How After-Market Exhaust Systems Can Disrupt Your Car’s Power Curve

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LIFE SUPPORT
The accelerator sequentially trips a column of distributed superconducting L-C circuits that shoves out the fluid with a magnetic piston. As the tray struck the floor and folded up against her body, the yank on her clit chain brought a scream from her throat before she fainted. It is very important to pay attention to tell-tale signs that something might be amiss. Just didnt think of carrots as a breakfast food? Quickly she realized she was immobile. As the laces became tighter and tighter, her feet were forced into a harsh en pointe position.

Stronger with Shield

Common Avian Emergencies

As I was saying, we got this rust infection about ten days out. I didn't have any more farm than an Eskimo. I cleaned the place out, sterilized, and reseeded. The infection was all through the ship and I couldn't chase it down. We finished that trip on preserved foods and short rations and I wasn't allowed to eat at the table the rest of the trip. I exhausted the air from an empty compartment, suited up, and drilled a couple of holes to the outside. Then I did a piping job to carry foul air out of the dark side of the ship in a fractional still arrangement — freeze out the water first, then freeze out the carbon dioxide.

Pesky thing was always freezing up solid and forcing me to tinker with it. But it worked well enough to get us home. Bart and Dan went off to do that, and Jim followed behind them. But from their faces, he could tell that their hopes weren't too high. Obviously, most of the oxygen had been put into the new extension, since there was more room there for the big containers of liquid oxygen. They had been in the shadow, below the main part of the hull, where they could stay liquid; but the heat of the fire had bent and twisted them, and some had even exploded violently.

Gauge will tell you what per cent has been used. It was a lot less than they would have liked. And we don't have chemicals to soak up the carbon dioxide they breathe out for even that long. In a vague way, Jim still felt responsible for the trouble. He should have checked on his assistant. He'd been beating his head, trying to remember what he'd learned in high school about the behavior of the gas. His father had always maintained that a man could accomplish almost anything by reducing things down to the basic characteristics, and then finding out what was done in other fields.

He realized his mistake before the others swung on him. What are the basic characteristics of carbon dioxide? The young man who'd studied chemistry piped up again.

Animals breathe it out, and plants breathe it in, releasing the oxygen again. It freezes directly to a solid, without any real liquid state, and is then known as dry ice. What about the cold side—does it get cold enough to freeze it out? Dan, any way to get a gastight pan. We could blow it through there slowly enough—trial and error should tell us how slowly. In most space program, they use two breathing mixes for the atmosphere inside the habitat modules and space suits.

Low Pressure pure oxygen at High pressure breathing mix is pretty close to ordinary Terran air at sea level. The important thing to note is that for a low pressure breathing mix, the crew will die of anoxia if the atmospheric pressure falls below 5. For a high pressure breathing mix, anoxia lies below The basic limit is anoxia ocurrs when the Partial Pressure of oxygen drops below 5.

Anoxia will hit the crew when the atmospheric pressure drops to what pressure? Low pressure is attractive; since it uses less mass and the atmosphere will escape more slowly through a meteor hole. Unfortunately the required higher oxygen level make living in such an environment as hazardous as chain-smoking inside a napalm factory.

NASA found that out the hard way in the Apollo 1 tragedy. Since then NASA always uses high pressure, they use low pressure in space suits only because they cannot avoid it. This does raise a new problem. There is a chance that the high-oxygen atmosphere will allow a meteor to ignite a fire inside the suit. There isn't a lot of research on this, but NASA seems to think that the main hazard is a fire enlarging the diameter of the breach, not an astronaut-shaped ball of flame.

There are other problems as well, the impossibility of air-cooling electronic components and the risk of long-term health problems being two.

A more annoying than serious problem with low pressure atmospheres is the fact that they preclude hot beverages and soups.

It is impossible to heat water to a temperature higher than the local boiling point. And the lower the pressure, the lower the boiling point. You may have seen references to this in the directions on certain packaged foods, the "high altitude" directions. The temperature can be increased if one uses a pressure cooker, but safety inspectors might ask if it is worth having a potentially explosive device onboard a spacecraft just so you can have hot coffee.

Decompression sickness also known as DCS, divers' disease, the bends or caisson disease is one of the more hideous dangers of living in space. It occurs when a person has been breathing an atmosphere containing inert gases generally nitrogen or helium and they move into an environment with lower pressure. This is commonly when they put on a soft space suit or the room suffers an explosive decompression. It has all sorts of nasty effects, ranging from joint pain and rashes to paralysis and death.

The large joints can suffer deep pain from mild to excruciating. The brain can have sudden mood or behavior changes, confusion, memory loss, hallucinations, seizures, and unconsciousness. The legs can become paralyzed. Headache, fatigue, malaise, loss of balance, vertigo, dizziness, nausea, vomiting, hearing loss, shortness of breath, and urinary or fecal incontinence: Why does it happen?

Well, imagine a can of your favorite carbonated soda beverage. Shake it up, and nothing happens. But when you open it, the soda explodes into foam and sprays everywhere.

When you open the container of shaken soda, you lower the pressure on the soda fluid. This allows all the dissolved carbon dioxide in the soda to un-dissolve, creating zillions of carbon dioxide bubbles, forming a foam. Now imagine that the carbon dioxide is nitrogen, the drink is the poor astronaut's blood in their circulatory system, and the foam is the deadly arterial gas embolisms.

That's what causes the bends. Please note that sometimes the bends can occur if one moves from one habitat to another that has the same pressure, but a different ratio of breathing mix the technical term is "Isobaric counterdiffusion".

Spacecraft of different nations or models could use different breathing mixes, beware. In fact, rival astromilitaries might deliberately utilize odd-ball breathing mixes, to make life difficult for enemy boarding parties invading their ships. The bends can be prevented by slow decompression , and by prebreathing.

Or by breathing an atmosphere containing no inert gases. Slow decompression works great for deep-sea divers but NASA does not favor it for space flight. An atmosphere with no inert gases pure oxygen is an insane fire risk.

NASA does not allow a pure oxygen atmosphere in spacecraft and space stations, but will allow it in space suit in a desperate attempt to lower the suit pressure to the point where the astronaut can move their limbs instead of being trapped into a posture like a star-fish. So NASA astronauts do a lot of prebreathing. This flushes nitrogen out of the blood stream. NASA uses Terra-normal pressure The astronaut s enter the airlock, and the airlock pressure is reduced to They breath pure oxygen through masks for 60 minutes because the air in the airlock contains nitrogen.

They then put on their space suits and do an EMU purge i. The air inside their suits is now also pure oxygen. The airlock pressure is then brought back up to the normal They then do minutes of in-suit prebreath. Of those minutes, 50 of them are light-exercise minutes and 50 of them are resting minutes.

Thus "Slow Motion Hokey Pokey". Now they are ready to open the airlock and step into space. The innovation was the 50 minutes of exercise. Without it, the entire protocol takes twelve hours instead of one hour and fifty minutes. If the habitat module's pressure was 12 psi an astronaut could use an 8 psi space suit with no prebreathing required a pity such suits are currently beyond the state of the art , and for a 4.

In case of emergency, when there is no time for prebreathing, NASA helpfully directs the astronauts to gulp aspirin, so they can work in spite of the agonizing pain.

Please note that most of the problem is due to the fact that soft space suits have a lower atmospheric pressure than the habitat module. So this can be avoided by using a hard space suit or space pod.

All of the atmospheric controls will be on the life support deck. On a related note, forced ventilation in the spacecraft's lifesystem is not optional. In free fall, the warm exhaled carbon dioxide will not rise away from your face. It will just collect in a cloud around your head until you pass out or suffocate. In the image above the blue dome shaped flame is an actual candle burning in free fall.

And in Clarke's "Feathered Friend", he talks about the wisdom of using an animal sentinel to monitor atmospheric quality. Specifically by using the tried and true "canary in a coal mine" technique. I know most people like to tie little prayer flags and scarves and stuff to the air-vent to make sure it's working, but back home we use wind chimes. You don't have to be looking at 'em to know they're working. They're not like the chimes they have back on Earth; these only have one note.

Most habs around Saturn do it that way — each compartment has a single note. That way, you can tell location of a faulty blower just by the change in the sound.

And let me tell you, they are not optional. If you take a set down for anything other than maintenance on the air-vent in question, you can get arrested. Of course they're loud! That's how you know they're working. But I know what you mean — when I first moved out to Titan, it took me a good month to get used to 'em. I was up all night most nights hearing chimes all over the hab ringing. It was like this constant drone with a few off notes every now and then to make sure you didn't relax.

I complained to anybody who'd listen, which was nobody. All I did was get myself a rep as another dumb groundhog fresh off the boat. The chimes didn't just bother me at night, either. In public spaces they make quiet conversation just about impossible. And I just about failed my first semester in school from being distracted. Seriously, if I hadn't still been under Immigrant's Probation, I would have had to do a public service sentence.

As it was, I did have to take the Habitat Orientation class again — listening to the damned wind chimes the whole time. But let me tell you — They were absolutely right to bust me. They confiscated my ear buds when I got caught so I didn't have them during a weekend maintenance cycle on the hab. We were living in a retired Trans-Chronian, the kind they used to have before the River -class came out. The counter-spinning rings were always breaking down or getting fatigued or some damn thing, so we only had gravity maybe five days a week.

My little sisters loved it — I'd play catch with them, with the toddler standing in as the ball. Anyway, the apartment had only pair of rooms, and my parents got one and the girls the other. I slept in a bag in the living room and lived out of a foot locker. One night I woke up from a dead sleep with the uncontrollable feeling that something was wrong.

I couldn't put my finger out what it was, but the effect was disturbing. I figured that I was just having trouble sleeping from the wind chimes when I realized that was what was wrong — I wasn't hearing the chimes. A glance up told me that the chimes in the living room were still going, but I really didn't need it. The sound of all the chimes in our apartment had gotten so far under my skin over the weeks we'd been living there that I pretty much figured out immediately which chimes had stopped.

You guessed it — the girls' room. By the time I got in there they were both awake and holding hands while spinning like they teach you. My parents were in there a couple seconds after me, but only because they had farther to go. Anyway, it was nothing much as vent problems go. A stuffed rabbit toy had gotten jammed into the fan — so the girls got grounded and had to do extra chores for a week. They whined about it, and kids do, and then we all went back to bed.

It took a me good while to go back to sleep after that. For all I my complaining about those annoying, distracting, aggravating wind chimes, if we didn't have 'em up that night my sisters would have never have woken up. Yeah, Fireproof is another absolute classic from grand-master Hal Clement. And it hammers home a hard truth you can find in Lazarus Long's notebooks. On Terra, being ignorant shortens your lifespan. Being willfully ignorant is just asking for it.

And being willfully ignorant in space means you are doing your darndest to cop a Darwin Award. You don't just need a good education to get a job in space, you need so you don't die. Read how that moron saboteur Hart thinks education is a waste of time. Up to when his flaming body gets splattered all over the wall because he thinks he's so smart. He thinks Nah, I don't need no stinkin' physics and chemistry!

That's the last thing that goes through his brain, besides the bulkhead. If Igno-Spy had ever had a high-school Science class he might have realized he was turning the inside of his jail cell into a freaking free-fall thermobaric weapon.

With him flicking his Bic at the fuse like Wile E. To conserve his oxygen supply, the curly-haired cadet had set the controls of his boat on a steady orbit around one of the larger asteroids and lay down quietly on the deck. One of the first lessons he had learned at Space Academy was, during an emergency in space when oxygen was low, to lie down and breath as slowly as possible.

And, if possible, to go to sleep. Sleep, under such conditions, served two purposes. While relaxed in sleep, the body used less oxygen and should help fail to arrive, the victim would slip into a suffocating unconsciousness, not knowing if and when death took the place of life.

Unpleasant odors in the air is a problem, but there is not much one can do about it. After all, you can't just open up a window to let in some fresh air, not in the vacuum of space. NASA carefully screens all materials, sealants, foods, and everything else to ensure that they do not emit noticeable odor in the pressurized habitat sections of spacecraft and space stations.

Such odors can quickly become overpowering in such tight quarters. There's a fortune awaiting the man who invents a really good deodorizer for a spaceship. That's the one thing you can't fail to notice. Oh, they try, I grant them that. The air goes through precipitators each time it is cycled; it is washed, it is perfumed, a precise fraction of ozone is added, and the new oxygen that is put in after the carbon dioxide is distilled out is as pure as a baby's mind; it has to be, for it is newly released as a by-product of the photosynthesis of living plants.

That air is so pure that it really ought to be voted a medal by the Society for the Suppression of Evil Thoughts. Besides that, a simply amazing amount of the crew's time is put into cleaning, polishing, washing, sterilizing - oh, they try!

But nevertheless, even a new, extra-fare luxury liner like the Tricorn simply reeks of human sweat and ancient sin, with undefinable overtones of organic decay and unfortunate accidents and matters best forgotten.

Once I was with Daddy when a Martian tomb was being unsealed - and I found out why xenoarchaeologists always have gas masks handy. But a spaceship smells even worse than that tomb. It does no good to complain to the purser. He'll listen with professional sympathy and send a crewman around to spray your stateroom with something which I suspect merely deadens your nose for a while. But his sympathy is not real, because the poor man simply cannot smell anything wrong himself.

He has lived in ships for years; it is literally impossible for him to smell the unmistakable reek of a ship that has been lived in - and, besides, he knows that the air is pure; the ship's instruments show it.

None of the professional spacers can smell it. But the purser and all of them are quite used to having passengers complain about the "unbearable stench" - so they pretend sympathy and go through the motions of correcting the matter. Not that I complained. I was looking forward to having this ship eating out of my hand, and you don't accomplish that sort of coup by becoming known first thing as a complainer.

But other first-timers did, and I certainly understood why - in fact I began to have a glimmer of a doubt about my ambitions to become skipper of an explorer ship.

But - Well, in about two days it seemed to me that they had managed to clean up the ship quite a bit, and shortly thereafter I stopped thinking about it. I began to understand why the ship's crew can't smell the things the passengers complain about.

Their nervous systems simply cancel out the old familiar stinks - like a cybernetic skywatch canceling out and ignoring any object whose predicted orbit has previously been programmed into the machine. But the odor is still there. I suspect that it sinks right into polished metal and can never be removed, short of scrapping the ship and melting it down.

Thank goodness the human nervous system is endlessly adaptable. His hole was on the eighth level, off a residential tunnel a hundred meters wide with fifty meters of carefully cultivated green park running down the center. The main corridor's vaulted ceiling was lit by recessed lights and painted a blue that Havelock assured him matched the Earth's summer sky.

Living on the surface of a planet, mass sucking at every bone and muscle, and nothing but gravity to keep your air close, seemed like a fast path to crazy. The blue was nice, though. Some people followed Captain Shaddid's lead by perfuming their air. Not always with coffee and cinnamon scents, of course. Havelock's hole smelled of baking bread. Others opted for floral scents or semipheromones.

Candace, Miller's ex-wife, had preferred something called EarthLily, which had always made him think of the waste recycling levels. These days, he left it at the vaguely astringent smell of the station itself.

Recycled air that had passed through a million lungs. The circle of life on Ceres was so small you could see the curve. He liked it that way. Infinitely more serious than annoying odors are harmful atmospheric contaminants. They share the same problem that a spacecraft cannot open the windows to bring in some fresh air. But unlike odors, these can harm or kill.

Basic atmospheric monitors will keep an eye on the breathing mix inside the habitat module for oxygen and carbon dioxide levels. But prudent spacecraft will have monitors for carbon monoxide and other deadly gases, hooked up to strident alarms.

In space no one can hear you scream, but in the habitat module's atmosphere everybody can hear that high-pitched squeaky wheel in the ventilator. And there may be permanent hearing loss from loud noises, say, from rocket engines. As a point of reference, the normal ambient noise level on the International Space Station is 60 db. Acoustic criteria are specified in terms of A-weighted sound level L A or equivalent A-weighted sound level L eq , where it is a specified time period, usually 8 or 24 hours.

The equivalent A-weighted sound level is defined as the constant sound level that, in a given situation and time period, conveys the same sound energy as the actual time varying A-weighted sound. The basic unit for these measurements is the decibel. Space station laboratory modules should have A-weighted sound levels not exceeding 55 dB a noise criterion curve of approximately 50 and reverberation times not exceeding 1.

These values should permit 95 percent intelligibility for sentences under conditions of normal vocal effort with the talker and the listener visible to each other. Environments with A-weighted sound levels above 55 dB will require assistance for adequate speech communication.

Designers of audiecommunication systems should recognize that the systems will amplify and distribute noise as well as speech signals to both intended and unintended listeners. Therefore, their use should be carefully controlled. For sleeping areas, background A-weighted sound levels below 45 dB are preferred, while levels up to 60 dB A are acceptable. Brief noises or transients during continuous noise backgrounds are particularly disturbing to sleep. The probability of full behavioral awakening increases with increasing sound level of the transient.

For transients with an L A of 60 dB, the probability of full behavioral awakening is about 0. The risk for producing significant hearing loss is negligible in noise exposures to an L eq24 of 80 dB. A hearing conservation program similar to that described by the Occupational Safety and Health Administration should be initiated for exposures to an L eq8 of 85 dB or more. If acoustic requirements for acceptable speech communication, sleep, and hearing conservation are met, problems of annoyance and task disruption will be minimal.

Vibration criteria are specified for linear vibration in the Hz frequency range. To reduce the probability of motion sickness, it is recommended that acceleration not exceed 2. Specific tasks requiring more stringent vibrational criteria should be analyzed on an individual basis.

In the absence of appropriate information, these tasks should be simulated on earth to determine vibration sensitivity and required accuracy. If head or finger control is required to an accuracy of 5mm rms or 2.

Hypergolics hiss too, with a harsher metallic note, bangs and pings. Hydroxy rockets , they roar. Solid packs are similar, but rougher, with underlying stutters and clicks. You hear it with your bones. Hard burn, in the jargon, refers to the practice of injecting a limited supply of antiprotons into the exhaust of a fusion torch for short, high-power bursts. Former astronaut Jay Buckey, now at Dartmouth Medical School in Hanover, New Hampshire, US, says that both temporary and permanent hearing loss were recorded after flights on the Soviet and Russian Salyut and Mir stations, even for stays as short as seven days.

The lost hearing was usually at higher frequencies. The living quarters of the ISS are the Russian Zvezda module, which is the noisiest module on the station. NASA says the goal is for the working area to have noise levels at or below 60 decibels dB and sleep bunks to be 50dB. At their peak several years ago, noise levels reached 72 to 78dB in the working area and 65 dB in the sleep stations. Decibels are measured on a logarithmic scale, meaning, for example, that 60dB is 10 times louder than 50dB.

NASA has worked to reduce the noise and its effect on the crew. By November , noise levels had been lowered to between 62 to 69dB in the work area and 55 to 60dB in the sleep compartments. Astronauts on the ISS used to have to wear ear plugs all day but are now only wear them for 2 to 3 hours per work day. According to the US National Institutes of Health, however, noise levels below 80dB are unlikely to lead to hearing loss, even with prolonged exposure.

But while the primary cause of hearing loss in general is high noise levels, Buckey suggested in a paper in Aviation Space and Environmental Medicine that several other factors might contribute to the problem in space. Elevated intracranial pressure, higher carbon dioxide levels and atmospheric contaminants may make the inner ear more sensitive to noise, he says. But there have been no studies yet to test these ideas. Buckey had designed a device to measure hearing loss of astronauts on the ISS, but his project was cancelled around the start of when NASA reduced funding for life sciences.

Crews have installed fan vibration isolators and mufflers on fan outlets, and acoustic padding to wall panels. The current crew, Russian cosmonaut Pavel Vinogradov and US astronaut Jeff Williams, installed a sound-insulating cover on the Russian carbon dioxide removal system. They also started adding acoustic padding near the Russian air conditioner.

Future crews will swap out 30 to 40 fans with quieter versions. Meteors are probably nothing to worry about. On average a spacecraft will have to wait for a couple of million years to be hit by a meteor larger than a grain of sand. But if you insist, there are a couple of precautions one can take.

First one can sheath the ship in a thin shell with a few inches of separation from the hull. This "meteor bumper" aka " Whipple shield " will vaporize the smaller guys. For larger ones, use radar. It is surprisingly simple. For complicated reasons that I'm sure you can figure out for yourself, a meteor on a collision course will maintain a constant bearing it's a geometric matter of similar triangles.

So if the radar sees an object whose bearing doesn't change, but whose range is decreasing, it knows that You Have A Problem. This happens on Earth as well.

If you are racing a freight train to cross an intersection, and the image of the front of the train stays on one spot on your windshield, you know that you and the engine will reach the intersection simultaneously. One can make an hard-wired link between the radar and the engines, but it might be a good idea to have it sound an alarm first. This will give the crew a second to grab a hand-hold. You did install hand-holds on all the walls, didn't you? And require the crew to strap themselves into their bunks while sleeping.

Having said that, Samuel Birchenough points out that anybody who has played the game Kerbal Space Program know that an object that is not on a fixed bearing can still hit you. If your spacecraft and the other object are in orbit around a planet, the object's bearing will be constantly changing up to the last few kilometers before the collision. The moon, now visibly larger and almost painfully beautiful, hung in the same position in the sky, such that he had to let his gaze drop as he lay in the chair in order to return its stare.

This bothered him for a moment -- how were they ever to reach the moon if the moon did not draw toward the point where they were aiming? It would not have bothered Morrie, trained as he was in a pilot's knowledge of collision bearings, interception courses, and the like. But, since it appeared to run contrary to common sense, Art worried about it until he managed to visualize the situation somewhat thus: It was a simple matter of similar triangles, easy to see with a diagram but hard to keep straight in the head.

The moon was speeding to their meeting place at about miles an hour, yet she would never change direction; she would simply grow and grow and grow until she filled the whole sky. To guard against larger stuff Captain Yancey set up a meteor-watch much tighter than is usual in most parts of space.

The only condition necessary for collision is that the other object hold a steady bearing-no fancy calculation is involved. The only action necessary then to avoid collision is to change your own speed, any direction, any amount.

This is perhaps the only case where theory of piloting is simple. Commander Miller put the cadets and the sublieutenants on a continuous heel-and-toe watch, scanning the meteor-guard 'scopes. Even if the human being failed to note a steady bearing the radars would "see" it, for they were so rigged that, if a "blip" burned in at one spot on the screen, thereby showing a steady bearing, an alarm would sound- and the watch officer would cut in the jet, fast!

A more practical study of any such device shows that any extraneous object that does not change its aspect angle is necessarily on a collision course. Ergo, any target that does not move causes the alarm to ring, and the autopilot to swerve aside. If the habitat module or space suit is punctured, all the air will start rushing out. Unless you and the other occupants want to experience first-hand all the many horrible ways that space kills you , you'd better patch that hole stat!

An instrument called a Manometer will register a sudden loss of pressure and trigger an alarm. Life support will start high-pressure flood of oxygen, and release some bubbles. The bubbles will rush to the breach, pointing them out to the crew.

The crew will grab an emergency hull patch thoughtfully affixed near all external hull walls and seal the breach. The emergency hull patches are metal discs. They look like saucepan covers with a rubber flange around the edge. They will handle a breach up to fifteen centimeters in diameter. Never slap them over the breach, place it on the hull next to the breach and slide it over. Once over the breach, air pressure will hold it in place until you can make more permanent repairs.

A more advanced alternative to bubbles are "plug-ups" or "tag-alongs". These are plastic bubbles full of helium and liquid sealing plastic. The helium is enough to give them neutral buoyancy, so they have no strong tendency to rise or sink. They fly to the breach, pop, and plug it with quick setting goo. Much to the relief of the crew caught in the same room with the breach when the automatic bulkheads slammed shut. Holden froze, watching the blood pump from Shed's neck, then whip away like smoke into an exhaust fan.

The sounds of combat began to fade as the air was sucked out of the room. His ears throbbed and then hurt like someone had put ice picks in them. As he fought with his couch restraints, he glanced over at Alex. The pilot was yelling something, but it didn't carry through the thin air. Naomi and Amos had gotten out of their couches already, kicked off, and were flying across the room to the two holes.

Amos had a plastic dinner tray in one hand. Naomi, a white three-ring binder. Holden stared at them for the half second it took to understand what they were doing. The world narrowed, his peripheral vision all stars and darkness. By the time he'd gotten free, Amos and Naomi had already covered the holes with their makeshift patches. The room was filled with a high-pitched whistle as the air tried to force its way out through the imperfect seals.

Holden's sight began to return as the air pressure started to rise. He was panting hard, gasping for breath. Someone slowly turned the room's volume knob back up and Naomi's yells for help became audible. She was pointing at a small red-and-yellow panel on the bulkhead near his crash couch. Years of shipboard training made a path through the anoxia and depressurization.

Inside were a white first aid kit marked with the ancient red-cross symbol, half a dozen oxygen masks, and a sealed bag of hardened plastic disks attached to a glue gun. He wasn't sure if her voice sounded distant because of the thin air or because the pressure drop had blown his eardrums. Holden yanked the gun free from the bag of patches and threw it at her.

She ran a bead of instant sealing glue around the edge of her three-ring binder. She tossed the gun to Amos, who caught it with an effortless backhand motion and put a seal around his dinner tray. The whistling stopped, replaced by the hiss of the atmosphere system as it labored to bring the pressure back up to normal.

Little gas-filled plastic balls swarm into the compartment. They range from golf-ball to tennis-ball size. A new man, I decide.

He's heard about the Commander. He's too anxious to look good. He's concentrating too much. Doing his job one part at a time, with such thoroughness that he muffs the whole. The plug-ups will drift aimlessly throughout the patrol, and will soon fade into the background environment. No one will think about them unless the hull is breached. Then our lives could depend on them. They'll rush to the hole, carried by the escaping atmosphere. If the breach is small, they'll break trying to get through.

A quick-setting, oxygen-sensitive goo coats their insides. The cat scrambles after the nearest ball. He bats it around. It survives his attentions. He pretends a towering indifference. He's a master of that talent of the feline breed, of adopting a regal dignity in the face of failure, just in case somebody is watching. Something strange filled her mouth and she could feel something down her throat as well. As she tried to breath, she quickly realized she could only breathe through her nose.

Before she could truly understand her predicament, she saw her Master enter the room. A shiver of true fear ran down her back. Do you know how embarrassing it was to apologize to all my guests? You should be better trained than that.

Corey's eyes watered as a gurgle escaped her throat. For the next four weeks you will be my toilet slave. She was in a bathroom, tied in a position beside a man's urinal.

This is a bathroom in a friend's dungeon. They have parties here every night and quite a lot through the day. You should have plenty of customers. I'll see you in a month. She had been ok with the humiliation, the pain and torture, the body piercings and the sexual servitude.

She had never imagined she would be forced to be an actual toilet. She was scared to death and, in her panic, released her bladder. A catheter inserted in her had been designed to pump her own urine into the large clear basin that had been positioned over her face.

A large funnel led from the basin into her mouth. As the tube deposited her own urine into her mouth, another tube locked into her throat prevented her from doing anything other than swallowing. Rubber wedges had been forced between her teeth, holding her mouth wide open.

The result was her mouth as a reservoir for anything deposited into the basin above her, including her own excretions. As her own urine filled her mouth and she was forced to swallow it, tears began flowing from her eyes. Three days had passed and Corey had been unable to move an inch. A servant arrived almost hourly to wrench her bonds tighter. She knew now that not just straps bound her body, but steel bands riveted to the wall and floor.

She would never be able to move again until the steel rivets where cut away. She had lost count of the number of men and women who had defecated or urinated into her basin. At first she had to fight the incredible urge to vomit as she felt her mouth filling with warm shit. She tried to scream before the partygoers relieved themselves, hoping to gain some sympathy. Instead they often smiled at the whimper that escaped her throat, and then tried even harder to fill the basin, forcing her to take more than the typical mouthful.

Corey had even lost the ability to cry. She knew now that she had fallen to the lowest level possible. Not even treated as an animal, now she was just a receptacle for a series of strangers.

It was a vicious cycle. Often, after a big party night, the waste of the guests would distend her stomach. She had consumed everything from plain urine to diarrhea.

In the middle of the night, after the last guest had urinated, she would urinate or defecate herself, feeling her own waste products pumped back up into the basin and into her mouth. It was at these times she felt she wanted to die.

But she could not do anything except swallow her own feces again. For seven long days she had been used as a toilet at the club. She was surprised when someone started cutting away the rivets to release her, hoping that her Master had actually forgiven her. Once released, she thought the worst was over.

She quickly discovered her Master was still very angry. She was blindfolded once again, unlocked from the wall and transported to another location. It was an hour before she was chained on a cold, dirt floor. Her blindfold was removed as someone plugged her nose with stoppers. Long hoses where cut through the center of the stoppers so that she could breathe. The other end of the hoses extended away from her body, up into the darkness above her. Rubber wedges once again held her mouth wide open, though her throat was blocked, preventing her from breathing through her mouth.

She could swallow once again, but only breathe with some difficulty through the long hoses in her nose. The steel collar was still locked around her throat with short chains from both sides that kept Corey on her knees. Her arms were still bound behind her back, rivets holding her wrists to the back of her collar. As the hands left her once again, she tried to cry out but the throat gag only allowed a gurgle.

Darkness quickly surrounded her. After a few hours, Corey could hear the roar of a crowd in the distance. Light streamed in from overhead suddenly and, as she looked up to see the source, a thin stream of urine poured down on her head. It was then she realized she had been chained in the bottom of a portable toilet. She could now hear the soccer game outside and she realized it would be a long weekend. By the end of the first week she had been buried up to her breasts in feces and urine.

She knew she would soon be submerged in shit, unable to prevent it from entering her mouth. Already, despite the tubes in her nose, she could barely stand the smell around her. Her hair was covered with brown waste, her head draped with a piece of used toilet paper.

All she could do was stay on her knees and endure with the knowledge that she might stay here for weeks. The stadium had apparently closed in early evening. The sounds of the crowd receded and she was left in darkness.

The waste now covered her to her neck. She truly felt worthless as she kneeled in the bottom of the toilet. She knew in several hours she would be completely covered in other people's feces, and she will have lost all identity as an individual. She was a toilet slave now, finding in her mind the acceptance of her new position.

Nothing else mattered now. Corey had been cleaned thoroughly by the other slaves, her body scrubbed hard to ensure she would not be offensive to any guests or the Master. She did not fight, nor object at all. Corey had reached the depths of humiliation. Just hours ago, after spending her second week in the same portable toilet, she had been buried beneath human feces. Only the breathing tubes that remained unblocked allowed her to breath.

Her mouth, held open wide by the rubber wedges and her throat blocked open, was quickly filled as well. Corey had been forced to swallow a lot of the shit around her. By the time her Master's slaves had pulled her out, she had truly become a toilet slave. Now, as she kneeled at her Master's feet again, she kept her head bowed. She was sure she would have to prove her dedication as a toilet slave soon. She was not disappointed.

One of the slave girls, a young girl of seemingly only 18 years old, was stretched across a hobby horse as a guest fucked her up the ass. The girl, obviously not enjoying the penetration, was trying to scream, but another man kept her mouth filled with his huge cock. Finally, the first man came deep into the slave's ass and pulled out. Moving to her mouth, he replaced the second man, who moved to come in her ass as well, while the slavegirl cleaned off both their cocks.

Corey's Master pulled her up and made her kneel behind the young slave. She knew she was lower than the girl in stature, lower than them all. Her Master whispered quietly in the young slave's ear and, as Corey penetrated the girls asshole with her tongue, she could feel a piece of feces being forced out.

Corey sucked harder, pulling the soft lump from the girl and swallowing it. Corey's two months where nearly up, though she was unaware of the time. She had spent the past three weeks on a steady diet of shit and urine, never allowed to consume anything else. Even the lowliest slave was allowed to use her as a toilet, pissing in her mouth as she drank without hesitation. During the day, with her arms still bound up high on her back, she was responsible for cleaning the floors and toilets in the bathroom with her tongue.

She licked the stains out of the bowls, cleaning the inside and outside until spotless, swallowing any debris she might find. At times, the guests would avoid flushing the toilets. Corey knew when she found one like this, that she was to eat and drink any contents. The few times guests or slaves where allowed to use a real toilet, Corey was kept close to act as toilet paper. On her last day, Corey was led into the living room where she saw two people. The owner of the escort company and Cindy sat on the couch.

Both looked surprised as they recognized Corey. The innocent young girl from the Midwest was gone. Instead, they saw a blonde girl, walking in ballet shoes, with harsh rings pierced through her clit, nose and twice through her nipples.

As she turned to kneel at her Master's feet, they could see the brutal method her arms had been forced up her back, then riveted to the back of her steel collar. Cindy could not believe her friend was in this body of a slave. As Corey fell to her knees with practiced ease and her chain leash was locked to a ring in the floor, her Master addressed her for the first time in a month.

But I have a better offer. If you chose to stay for a complete year, I will pay you one million dollars. In truth, I will pay half to a trust fund now, with the other half held in escrow until the final date of your servitude. She was his toilet slave and couldn't understand the discussion of money. Have I displeased you? You were everything I could dream of. But I want to keep you for a year. He wants to keep you as a slave. But you don't have to do it. We will take you away for a few days to recover anyway, so you can make your decision later.

She looked back in confusion, unsure of what was happening. Two days had passed for Corey. At home again, she found it strangely surreal to be without her body in some sort of bondage.

Her various piercings had been removed, but all had been replaced with small bars or plugs, keeping them open in case Corey should decide to return. She had the use of her arms for the first time in two months, though she found it strange. Her feet had also not adapted. The long term wear of ballet shoes made standing flatfooted impossible.

She found herself wearing her five inch heels day and night, while asking Cindy to buy her even higher heels. She was not comfortable. Something had changed in her, making her normal life of modeling and acting seem less important, distantly unfamiliar. Even though she had plenty of money in the bank her priorities seemed to have changed now that she had enough money to do anything she wanted.

Rather than looking into buying headshots, she found herself surfing the internet for kinky clothes. Nights were the most difficult until Cindy purchased her own butt plug.

As she inserted it for the first time, she felt a familiar thrill from the pain. It was the best night of sleep she had since she returned. Cindy tried to be of help, but could only provide a distraction from Corey's thoughts. Though she refused to discuss her experience, she knew that she had been used and tortured mercilessly.

Despite her fear of what had been done to her, she knew she would still consider the offer her "Master" had made. It had been four weeks since Corey had returned from her traumatic job and Cindy hoped that the effects of her two-month stint as a slave had finally faded. She rang the bell a second time, glancing at her watch. Finally, she knocked on the door.

As she spoke, her knocks dislodged the door, which swung open on its own. The door had been open the whole time. Confused and somewhat concerned, she cautiously pushed open the door.

Cindy impatiently waited in Mr. After finding what she felt were signs that her friend Corey had been abducted, Cindy had turned to the most likely conclusion; her former client, the one who had hired her as a slave for two months, had come to take her back. She was terrified of the police, so turned to her boss instead.

She sat uncomfortably in the hard wood chair, subconsciously pulling on her skirt to cover more of her legs. After years working as an escort, she had grown accustomed to wearing sexy clothing, but she also knew that Mr.

Stanley was a lecher. She had spent the past two years in his employ, but all that time pointedly avoiding any personal contact. As she considered this, she suddenly felt exposed. Her t-shirt felt too tight, highlighting her 34D breasts too much, while her skirt fit snug around her contrasting inch waist. Despite this, she felt relief when Mr.

Stanley returned to his office, if only to get help for her endangered friend. Immediately his eyes dropped to her breasts. She tried to ignore it. Her voice quivered regardless. Stanley said, turning his attention to his desk and the work upon it. Stanley stopped at that, his attention returning to Cindy as he pulled off his glasses. She was sure that was what happened. Though she had never seen it in person, thankfully, she had heard rumors from other girls of agencies that often facilitated abductions.

In that moment, she realized what she had to do. Stanley looked at her, a skeptical expression on his face. Can you do it? I doubt I could get you on a guest list, and security is very tight. For years he had offered her lucrative jobs with men and women looking for a submissive brunette like her, but she had always turned him down. If I can get in there, maybe I can find her and get her back.

Stanley took a sip of his drink sitting on the table before leaning closer. His look was dead serious. She had little choice if she wanted to rescue her friend. She had never been a fan of any pain, much less the type of sexual torture she knew this buyer had in mind.

With that in mind, and ignoring the voice deep down that told her this would be different, she looked up to Stanley. Though she wanted desperately to cry out, to plead for mercy, some thread of her being still clung to the idea that she was playing the role of the perfect masochist.

Instead, she fought the urge as she had so many times before, trying to calm her own fears as she swung quietly in the early evening air. She had become quite accustomed to her new role over the days since she had joined the household, if being constantly in pain was anything you could grow accustomed to.

Each day, sometime early in the morning, after she was extracted from the multi-layer body bag she was kept in at night, Cindy was led naked from the basement dungeons on the end of a leash, her arms still bound with elbows touching behind her as they had been when Stanley had packed her.

The ache in her shoulders continued, but the coming predicament would quickly overwhelm the petty pain of her arms. Just as her arms had remained bound and thus useless, her jaw had grown accustomed to massive distention.

A huge ball gag remained jammed between her jaws, the strap pulled so tight that no amount of force by her tongue would dislodge it. Positioned standing in the center of the room, a man she was certain was not her new owner took a thin leather strap and wound it slowly and tightly around the base of each breast.

Halfway through the process, even as Cindy found herself moaning from the intense constriction, he would slip the strap through metal rings positioned on the outside and inside of each breast, clearly to provide a connection point for the overhead chains that she would soon dangle from. Once the strap had been wound, the chains would be lowered enough to attach to the four rings, then pulled toward the ceiling again. She would grunt as the bulk of her weight began to rest on her already tortured breasts, her toes reaching for the floor in a futile effort to relieve some of the pressure.

Her long brunette hair, placed in a tight ponytail with a strap included in the intricate style, was unceremoniously pulled down to a ring set in the floor beneath her. Her toes were quickly pulled away from the floor as her breasts were used as a pivot and her head as a lever. The strap was shortened until her body was pulled level to the floor. The strain on her neck was intense, and as she found herself staring at the back wall of the room, she could only moan from the pain building in both her neck and scalp.

Thin rope was then looped around her big toes, which were then folded beneath her, the toe ropes connected to the strap pulling her head to the floor, joining it mid way between. Pulled tight, the strained forced her neck back further while her back was arched painfully, a pain that would grow in intensity throughout the day.

Ropes attached to her knees and to poles on either side of her pulled her legs wide to expose her crotch. A variety of adjustments were made on the first morning to place her body at chest level to the man who bound her. As she was left for the first time, she quickly found herself alone. She had assumed, like in any sexual game, she would be positioned for the entertainment of an audience, or at least her new master.

But instead, she was alone, unwatched, untouched. The slight stirring of the air in the large room was the only thing keeping her company. On the second day of her role as decoration, she had been visited by another man after she was suspended, who in a brutal and efficient method pierced her body.

The session left rings at the base of her nipples, with rods near the tip, two clit rings, one inside the other, and a thick nose ring. Once his work was done, he left her alone once again. Cindy cried for what felt like hours, until she had no more tears. She had never wanted any type of modifications to her body, but now she not only had dual nipple piercings, she also felt the weight of the thick septum ring.

Her clit rings, though painful, were a distant ache that she could barely feel amongst the other torment she was enduring. It was then she began to realize, at least in part, what it meant to be a pain slave.

She found herself repeating only one word behind the gag, and this in almost a whisper through her own weakened voice. The hands touched her breasts, and even the lightest caress felt uncomfortable, as she knew they had turned red and sensitive from their constriction. But the hands disappeared, replaced suddenly by an explosion of pain on her inner thighs.

She bucked from the stroke of what she saw later was a harsh bamboo cane, but soon found there was no escape. A wail of fear erupted from her throat as another, and another stroke fell on her exposed thighs. Cindy lost count after the thirtieth stroke to her thighs, her mind a fog of pain and semi consciousness.

Her thighs felt like they were on fire, the series of welts growing by the second, as was the intense pain that emanated from each one.

Eight days earlier, Mr. Stanley had called Cindy at her apartment to tell her that everything had been arranged. Can you stand that long? She found Stanley in his office, a pile of strange material on his coffee table. He noticed her as she entered, then followed her gaze. Stanley started to arrange the gear Cindy began to get a little nervous.

She had been hired by clients in the past to do almost everything sexual, but being exposed to Mr. He was her boss, and a lecher, a combination that made her strive to avoid being in a compromising position around him. Cindy hesitated for a moment before she realized she had no choice. As her panties dropped to the floor, leaving her naked, she felt self-conscious as Stanley looked over her body with salivating eyes.

Cindy, angry at his response, put her hands on her hips and threw back her hair. He ignored her attitude, instead taking her offer, examining her thin, athletic body and long legs, before dragging his eyes over her large breasts and to the equipment he had laid out.

Stanley approached her, then carefully attached a series of adhesive pads to her body. Two small pads went over her nipples, with six additional pads around each of her breasts themselves, on her stomach, pressed over her clit, the small space between her pussy and anus, on her inner thighs and finally the soles of her feet.

He seemed to take his time, which only made Cindy angrier, but her anger distracted her from asking the purpose of all the pads. Wires extending from each gave little clue to their purpose. Once finished, he handed her a rubber cat suit. Cindy looked at the small outfit, wondering how it would stretch to fit her body, but began pulling it on her.

As she reached her crotch, Stanley stopped her, handing her two metal dildos. She looked at the cool steel, realizing she would need lube. She was far from turned on by her predicament. Not seeing any, and not wanting to ask Stanley, she resorted to sticking the dildo into her mouth, sucking and licking it to get it wet, before pressing it into her pussy.

She felt a flush of embarrassment as she found herself sucking the butt plug next, realizing she would soon be pushing it into her own ass. She gasped as the metal slid with some effort inside of her as well, making her gasp as they both filled her completely. She ignored their intrusion and began pulling up the suit. Stanley made sure the wires were fed from her body out the back of the suit, including wires that now extended to the two dildos inside of her.

Despite the earlier impossibility of fitting, Cindy soon found the suit stretched fully over her body. He handed her a rubber hood next, and as it fit smooth over her face he zipped it up in back. As he pulled it tight, forcing her elbows together, he could hear Cindy gasp.

A series of straps were laced around her legs, locking ankles, knees and thighs tightly together. It was intentionally too small, designed so that once it was properly laced on, the wearer would be completely unable to move. Consider this a warm-up. Already her shoulders had started to ache and the leather suit was removing any ability she would have to move.

A feature she had failed to notice as she had been put into it involved her feet. Rather than being allowed to stick up, her toes were pushed into a point parallel to her body.

As the laces became tighter and tighter, her feet were forced into a harsh en pointe position. As Stanly tightened a strap over her feet, he forced them to even curl back a little. She bit her lip instead, fighting back tears, as Stanley continued the process of strapping her into immobility. The suit reached up to her neck, but Stanley stopped before lacing that part.

He selected a leather hood first. Designed to work with the body bag, the hood extended down her neck and over her shoulders. The thick leather over her neck and body was built with rigid boning, much like a corset, intended to remove any chance of head motion. The hood itself was thick, with added padding over her ears and eyes. Only grommets were left for her nostrils, allowing the small favor of breathing. Before positioning the hood, Stanley peered under it.

As he began stuffing her mouth with the gag, she could hear his final words. It took another two hours to make it as tight as possible. What was left made Stanley feel even more horny. Cindy was reduced to a solid leather form, a smooth surface from head to toe. He took the wires from the pads and dildos, and attached them to a small box that would clip on to the suit. With a flick of a switch he knew the random shocks had begun. For a moment he watched, but could see no motion.

He flipped off the lights and left Cindy for the night. Inside the suit, Cindy was desperately struggling for release. The first shocks, a combination to her nipples and ass, made her scream into the harsh leather padding now stuffing her mouth beyond capacity.

These were no soft electrical impulses; every shock was like fire burning her, the effect coursing through her body for seconds after the actual shock had occurred. The first shock to her clit almost made her faint, followed by a long shock to her pussy, then to the soles of her feet. She bucked in response, the eye pads already dampened by tears. But despite her attempts to move, she knew she was being held rigid, and no escape on her own would be possible.

It was then that her claustrophobia began to set in. She hated tight spaces, and even panicked in total darkness. Stanley had laced her in the hood, but now she began to wail for escape. Her arms, already numb from the pain of their harsh bondage, were useless, as was the rest of her body. She was desperate for release, but found not the least of slack in her bondage. Her wails turned to sobs as he was forced to endure, and the first three minutes passed in silence in the office.

It was this way, two days later that Cindy was delivered to her new Master. She was the perfect mummified beauty, and a new found cruelty was borne inside of him. It was only the evening of the second day, a full 48 hours after he had placed the beautiful young girl in bondage, that he gave in and delivered her to her new Mater.

For Cindy it could have been a lifetime. Her mind had almost accepted her new fate, that as an immobile object of torture. As the laces were finally cut and the bag pealed away from her latex covered body, she sobbed in relief. Exhausted and terrified, she could do little to resist as she was suspended for her first day in the living room. She never set eyes on the man she both despised and feared, nor was she given the opportunity to ask. Her life became a routine; each night she was placed back in the extreme body bag Mr.

Stanley had delivered her in, complete with shock pads. The only additions were a feeding tube fed down into her stomach, a catheter and a new metal butt plug that incorporated an enema attachment. She found herself enduring nearly constant pain, so much so that even during the nights, when she was sure she had been forgotten and left for not hours but months, she felt some form of sleep wash over her.

But soon morning came, and with that she was suspended again. After only six days she felt like she was ready to break, as she struggled to hang on to a thread of her sanity, and her plan to rescue her friend. On what she determined was the eighth day, the routine was broken. Removed from her body bag, two rubber clad slaves carried her weakened form into a shower and cleaned her thoroughly.

Though she had never seen outfits like these, she felt a kindred spirit with the obviously tortured slaves. Their bodies covered in full black rubber from head to toe, she had difficulty understanding how they could see, much less breathe. They seemed to be a nearly rigid form, with what appeared to be harsh corsets under their rubber outfits holding both of their waists to tiny proportions.

Inflation bulbs dangled from between their legs, as did a catheter tube, connected to piss bags strapped to their thighs. Another tube, this from what was most likely a butt plug, traced up their backs to amber bags of some fluid strapped between their shoulder blades. She realized that both girls suffered a constant enema, with release only allowed by their master.

Despite her fatigue, she found she enjoyed the washing, completely forgetting that she was completely unshackled and able to break free. She was dried, her body powdered and hair gently brushed, Cindy moaned with pleasure as the slave carefully untangled the remnants of the ponytail. Of all things, she was most proud of her long hair, which now reached down to the middle of her back, a natural wave giving it a bouncy, shiny look.

Other elements produced by carbochlorination include titanium, potassium, manganese, chromium, sodium, magnesium, silicon and also with the use of plastic filters the nuclear fuels U and Th. Both C and Cl2 must be carefully recycled the recycling equipment dominates the system mass and replenished by regolith scavenging.

Lunar and asteroidal surface materials are ubiquitous and abundant sources of metals like silicon, aluminum, magnesium, iron, calcium, and titanium. Many schemes have been proposed for extracting these metals and oxygen for structural, electrical, and materials processing space operations.

However, all the metals burn energetically in oxygen and could serve as in-situ rocket fuels for space transportation applications. Table 1 lists the specific heats of combustion enthalpy at K and corresponding specific impluses at selected mixture ratios with oxygen of the above pure metals assuming rocket combustion at psia and an expansion ratio of Hydrogen is included for comparison. All the metals appear to offer adequate propulsion performance from low or moderate gravity bodies and are far more abundant than hydrogen on many terrestrial planets and asteroids.

It is noteworthy that silicon, the most abundant nonterrestrial metal, is potentially one of the best performers. In addition, iron with the lowest specific impulse is sufficiently energetic for cislunar and asteroidal transportation. Further, silicon and iron are the most readily obtained nonterrestrial metals. They can be separated by distillation of basalts and other nonterrestrial silicates in vacuum solar furnaces.

Efficient rocket combustion of metal fuels could be realized by injecting them as a fine powder into the combustion chamber. This could be done by mixing the fuel with an inert carrier gas or in liquid oxygen LOX to form a slurry.

Lean fuel mixtures would be used to achieve the maximum specific impluse by reducing the exhaust molecular weight without excessivly lowering the combustion temperature.

Two phase flow losses are estimated to be acceptable for anticipated throat sizes based on measured thrust loss data from solid rocket motors ustng aluminized propellants.

The metals could be atomized by condensing droplets in vacuum from a liquid metal stream forced through a fine ceramic nozzle. Brittle metals like silicon and calcium might be pulverized to sub 20 micrometer size in vacuum in autogenous grinders that operate by centrifugal impact and are independent of the gravity level. Atomic hydrogen is also called free-radical hydrogen or "single-H". The problem is that it instantly wants to recombine. Free radicals are single atoms of elements that normally form molecules.

Free radical hydrogen H has half the molecular weight of H 2. Free radicals extracted by particle bombardment are cooled by VUV laser chirping, and trapped in a hybrid laser-magnet as a Bose-Einstein gas at ultracold temperatures.

A Pritchard-Ioffe trap keeps their mobile spins aligned, using the interaction of the atomic magnetic moment with the inhomogeous magnetic field. Free radical deuterium that has been spin-vector polarized is stable against ionization and atomic collisions.

Because of its large fusion reactivity cross-sectional area, it makes a useful fusion fuel. Most of the data here is from Metallic Hydrogen: Silvera and John W.

Hydrogen H 2 subjected to enough pressure to turn it into metal mH , then contained under such pressure. Release the pressure and out comes all the stored energy that was required to compress it in the first place.

It will require storage that can handle millions of atmospheres worth of pressure. The mass of the storage unit might be enough to negate the advantage of the high exhaust velocity. The hope is that somebody might figure out how to compress the stuff into metal, then somehow release the pressure and have it stay metallic. That is, if the pressure on metallic hydrogen were relaxed, it would still remain in the metallic phase, just as diamond is a metastable phase of carbon.

This will make it a powerful rocket fuel, as well as a candidate material for the construction of Thor's Hammer. Then that spoil-sport E. Salpeter wrote in "Evaporation of Cold Metallic Hydrogen" a prediction that quantum tunneling might make the stuff explode with no warning.

Since nobody has managed to make metallic hydrogen they cannot test it to find the answer. Silvera and Cole figure that metallic hydrogen is stable, to use it as rocket fuel you just have to heat it to about 1, K and it explodes recombines into hot molecular hydrogen. Recombination of hydrogen from the metallic state would release a whopping megajoules per kilogram.

TNT only releases 4. This would give metallic hydrogen an astronomical specific impulse I sp of 1, seconds.

Yes, this means metallic hydrogen has more specific impulse than a freaking solid-core nuclear thermal rocket. I sp of 1, seconds is big enough to build a single-stage-to-orbit heavy lift vehicle, which is the holy grail of boosters. The high density is a plus, since liquid hydrogen's annoyingly low density causes all sorts of problems. Metallic hydrogen also probably does not need to be cryogenically cooled, unlike liquid hydrogen. Cryogenic cooling equipment cuts into your payload mass.

The drawback is the metallic hydrogen reaction chamber will reach a blazing temperature of at least 6, K. By way of comparison the temperatures in the Space Shuttle main engine combustion chamber can reach 3, K, which is about the limit of the state-of-the-art of preventing your engine from evaporating.

It is possible to lower the combustion chamber temperature by injecting cold propellant like water or liquid hydrogen. The good part is you can lower the temperature to 3, K so the engine doesn't melt. The bad part is this lowers the specific impulse nothing comes free in this world. But even with a lowered specific impulse the stuff is still revolutionary. At atmospheres of pressure in the combustion chamber it will be an I sp of 1, sec with a temperature of 7, K. At 40 atmospheres the temperature will be 6, K, still way to high.

Injecting enough water propellant to bring the temperature down to 3, to 3, K will lower the I sp to to seconds. Doing the same with liquid hydrogen will lower the I sp to 1, to 1, seconds. Two electrons in a helium atom are aligned in a metastable state one electron each in the 1s and 2s atomic orbitals with both electrons having parallel spins, the so-called "triplet spin state", if you want the details.

When it reverts to normal state it releases 0. Making the stuff is easy. The trouble is that it tends to decay spontaneously, with a lifetime of a mere 2. And it will decay even quicker if something bangs on the fuel tank.

Or if the ship is jostled by hostile weapons fire. To say the fuel is touchy is putting it mildly. The fuel is stored in a resonant waveguide to magnetically lock the atoms in their metastable state but that doesn't help much. There were some experiments to stablize it with circularly polarized light, but I have not found any results about that. Meta-helium would be such a worthwhile propulsion system that scientists have been trying real hard to get the stuff to stop decaying after a miserable 2.

One approach is to see if metastable helium can be formed into a room-temperature solid if bonded with diatomic helium molecules, made from one ground state atom and one excited state atom. This is called diatomic metastable helium. The solid should be stable, and it can be ignited by heating it. Theoretically He IV-A would be stable for 8 years, have a density of 0. The density is a plus, liquid hydrogen's annoying low density causes all sorts of problems. Robert Forward in his novel Saturn Rukh suggested bonding 64 metastable helium atoms to a single excited nitrogen atom, forming a stable super-molecule called Meta.

Whether or not this is actually possible is anybody's guess. In theory it would have a specific impulse of seconds. Metastable helium is the electronically excited state of the helium atom, easily formed by a 24 keV electron beam in liquid helium. Spin-aligned solid metastable helium could be a useful, if touchy, high thrust chemical fuel with a theoretical specific impulse of 3. Electromagnetic ion thrusters use the Lorentz force to move the propellant ions.

Helicon Double Layer Thruster. Magnetoplasmadynamic thruster , a travelling wave plasma accelerator. Propellant is potassium seeded helium. Impulsive electric rockets can accelerate propellant using magnetoplasmadynamic traveling waves MPD T-waves.

In the design shown, superfluid magnetic helium-3 is accelerated using a megahertz pulsed system, in which a few hundred kiloamps of currents briefly develop extremely high electromagnetic forces. The accelerator sequentially trips a column of distributed superconducting L-C circuits that shoves out the fluid with a magnetic piston. The propellant is micrograms of regolith dust entrained by the superfluid helium. Each J pulse requires a millifarad of total capacitance at a few hundred volts.

Compared to ion drives, MPDs have good thrust densities and have no need for charge neutralization. However, they run hot and have electrodes that will erode over time. Moreover, small amounts of an expensive superfluid medium are continually required. One of my mentors, Dr. Jones of the University of Arizona, has worked out the physics of this.

A plasmoid rocket creates a torus of ball lightning by directing a mega-amp of current onto the propellant. Almost any sort of propellant will work. The plasmoid is expanded down a diverging electrically conducting nozzle. Magnetic and thermal energies are converted to directed kinetic energy by the interaction of the plasmoid with the image currents it generates in the nozzle. Unlike other electric rockets, a plasmoid thruster requires no electrodes which are susceptible to erosion and its power can be scaled up simply by increasing the pulse rate.

The design illustrated has a meter diameter structure that does quadruple duty as a nozzle, laser focuser, high gain antenna, and radiator. Laser power 60 MW is directed onto gap photovoltaics to charge the ultracapacitor bank used to generate the drive pulses.

The variable specific impulse magnetoplasma rocket is a plasma drive with the amusing ability to "shift gears. Three "gears" are shown on the table.

There are more details here and here. A chemical rocket tug would require 60 metric tons of liquid oxygen - liquid hydrogen propellant. Granted the VASIMR tug would take six month transit time as opposed to the three days for the chemical, but there are always trade offs. Propellant typically hydrogen, although many other volatiles can be used is first ionized by helicon waves and then transferred to a second magnetic chamber where it is accelerated to ten million degrees K by an oscillating electric and magnetic fields, also known as the ponderomotive force.

Franklin Chang-Diaz, et al. Electrostatic ion thrusters use the Coulomb force to move the propellant ions. Ernst Stuhlinger, a leading authority on electric ion propulsion, has often said that such a rocket system would be ideal for a manned journey to Mars. What the joke is saying is that electrostatic drives are power hogs.

Solar power is relatively lightweight but the energy is so dilute you need huge arrays. Nuclear power can supply megawatts of power, but reactors have a mass measured in tons. But the joke is on the wag. Turns out there is such a thing as an extension cord long enough, it is called beamed power. This is where the spacecraft has a relatively lightweight power receptor, while back at home is a kilometers-wide solar power station that gathers gigawatts of power and beams it to the spacecraft via microwave beam or laser.

The beam becomes the extension cord. When I was a little boy, the My First Big Book of Outer Space Rocketships type books I was constantly reading usually stated that ion drives would use mercury or cesium as propellant. But most NASA spacecraft are using xenon. Ionization energy represents a large percentage of the energy needed to run ion drives. In addition, the propellant should not erode the thruster to any great degree to permit long life; and should not contaminate the vehicle.

Many current designs use xenon gas, as it is easy to ionize, has a reasonably high atomic number, is inert and causes low erosion. However, xenon is globally in short supply and expensive. Older designs used mercury, but this is toxic and expensive, tended to contaminate the vehicle with the metal and was difficult to feed accurately. Other propellants, such as bismuth and iodine, show promise, particularly for gridless designs, such as Hall effect thrusters.

Field-Emission Electric Propulsion typically use caesium or indium as the propellant due to their high atomic weights, low ionization potentials and low melting points. Central City and the other bases that had been established with such labor were islands of life in an immense wilderness, oases in a silent desert of blazing light or inky darkness. There had been many who had asked whether the effort needed to survive here was worthwhile, since the colonization of Mars and Venus offered much greater opportunities.

But for all the problems it presented him, Man could not do without the Moon. It had been his first bridgehead in space, and was still the key to the planets. The liners that plied from world to world obtained all their propellent mass here, filling their great tanks with the finely divided dust which the ionic rockets would spit out in electrified jets. By obtaining that dust from the Moon, and not having to lift it through the enormous gravity field of Earth, it had been possible to reduce the cost of spacetravel more than ten-fold.

Indeed, without the Moon as a refueling base, economical space-flight could never have been achieved. The spacecraft then will attempt to redirect the object into a stable orbit around the moon. Within that limited ARM context, a conservative engineering approach using an existing deep-space propulsion system e. Our interest in near Earth objects NEOs should be more expansive than one or a few missions, though. This essay examines an alternative propulsion system with substantial promise for future space industrialization using asteroidal resources returned to HEO.

Electrostatic propulsion is the method used by many deep space probes currently in operation such as the Dawn spacecraft presently wending its way towards the asteroid Ceres. For that probe and several others, xenon gas is ionized and then electrical potential is used to accelerate the ions until they exit the engine at exhaust velocities of 15—50 kilometers per second, much higher than for chemical rocket engines, at which point the exhaust is electrically neutralized.

This method produces very low thrust and is not suitable for takeoff from planets or moons. However, in deep space and integrated over long periods of engine operation time, the gentle push of an ion engine can impart a very significant velocity change to a spacecraft, and do so extremely efficiently: The solar system has planets, asteroids, rocks, sand, and dust, all of which can pose dangers to space missions.

The larger objects can be detected in advance and avoided, but the very tiny objects cannot, and it is of interest to understand the effects of hypervelocity impacts of microparticles on spacesuits, instruments and structures. For over a half century, researchers have been finding ways to accelerate microparticles to hypervelocities 1 to kilometers per second in vacuum chambers here on Earth, slamming those particles into various targets and then studying the resultant impact damage.

These microparticles are charged and then accelerated using an electrical potential field. It is a natural step to consider, instead of atomic-scale xenon ions, the application to deep space propulsion of the electrostatic acceleration of much, much larger microparticles:.

However, their high exhaust velocity is poorly matched to typical mission requirements and therefore, wastes energy. A better match would be intermediate between the two forms of propulsion. This could be achieved by electrostatically accelerating solid powder grains. Several papers have researched such a possibility. There are many potential sources of powder or dust in the solar system with which to power such a propulsion system.

NEOs could be an ideal source, as hinted at in a presentation:. Asteroid sample return missions would benefit from development of an improved rocket engine… This could be achieved by electrostatically accelerating solid powder grains, raising the possibility that interplanetary material could be processed to use as reaction mass.

Imagine a vehicle that is accelerated to escape velocity by a conventional rocket. It then uses some powder lifted from Earth for deep-space propulsion to make its way to a NEO, where it lands, collects a large amount of already-fractured regolith, and then takes off again. It is already known that larger NEOs such as Itokawa have extensive regolith blankets. Furthermore, recent research suggests that thermal fatigue is the driving force for regolith creation on NEOs ; if that is true, then even much smaller NEOs might have regolith layers.

Additionally, some classes of NEOs such as carbonaceous chondrites are expected to have extremely low mechanical strength; for such NEOs, it would be immaterial whether or not pre-existing regolith layers were present, as the crumbly material of the NEO could be crushed easily. After leaving the NEO, onboard crushers and grinders convert small amounts of the regolith to very fine powder. These processes would be perfected in low Earth orbit using regolith simulant long before the first asteroid mission.

Electrostatic grids accelerate and expel the powder at high exit velocities. Not all of the regolith onboard is powdered, only that which is used as propellant: The Dawn spacecraft consumes about grams of xenon propellant per day.

For asteroid redirect missions, a much higher power spacecraft with greater propellant capacity than Dawn is needed, and NASA is considering one with kilowatt arrays and 12 metric tons of xenon ion propellant , versus just 0. If that 12 metric tons were consumed over a four-year period, then that would equate to 8.

The machinery required to collect, crush, and powder a similar mass of regolith per hour need not be extremely large because initial hard rock fracturing would not be required. It is plausible that the entire system—regolith collection equipment, rock crushing, powdering, and other material processing equipment—might not be much larger than the 12 metric tons of xenon propellant envisioned by NASA. One of the attractions of the scheme described here is that this system could be started with one or a few vehicles, and then later scaled to any desired throughput by adding vehicles.

Suppose that, on average, a single vehicle could complete a round-trip and return tons of asteroidal material to HEO once every four years. After arrival in HEO, maintenance is performed on the vehicle. Some of the remaining regolith is powdered and becomes propellant for the outbound leg of the next NEO mission. A fleet of ten such vehicles could return 1, tons per year on average of asteroidal material, while a fleet of such vehicles could return 10, tons per year.

The system described is scalable to any desired throughput by the addition of vehicles. Mass production of such vehicles would reduce unit costs. A system of many such vehicles would be resilient to the failure of any single one. If one of the many vehicles were lost, then the throughput rate of return of asteroidal material to HEO would be reduced, but the system as a whole would survive.

Replacement vehicles could be launched from Earth, or perhaps the failed vehicle could also be returned to HEO for repair by one of the other vehicles. The scheme discussed in this essay would use powdered asteroidal regolith instead of xenon, and would save not only the material cost of the xenon ion propellant itself, but also the vastly larger cost of launching that propellant from Earth each time.

Over several or many missions, the initial cost of developing the powdered asteroid propulsion approach would justify itself economically. Over dozens or hundreds of missions, the asteroidal material returned to HEO could serve as radiation shielding, as a powder propellant source for all sorts of beyond-Earth-orbit missions and transportation in cislunar space, and as input fodder for many industrial and manufacturing processes, such as the production of oxygen or solar cells.

All of this advanced processing could be conducted in HEO, where a telecommunications round-trip of a second or two would allow most operations to be economically controlled from the surface of the Earth using telerobotics.

By contrast, the processing that happens outside of Earth orbit would be limited to the collection, crushing, and powdering of regolith. These latter and simpler processes would be completed largely autonomously. Low Earth orbit LEO is reachable from the surface of the Earth in eight minutes, and geosynchronous orbit—the beginning of HEO—is reachable within eight hours.

The proximity of LEO and HEO to the seven billion people on Earth and their associated economic activity is a strong indication that cislunar space will become the future economic home of humankind. In the architecture described here, raw material is slowly delivered to HEO over time via a fleet of regolith-processing, electrostatically-propelled vehicles; by contrast, humans arrive quickly to HEO from Earth.

This NEO-based ISRU architecture could be the foundation of massive economic growth off-planet, enabling the construction mostly from asteroidal materials of massive solar power stations, communications hubs, orbital hotels and habitats, and other facilities. One of the ideas I had been thinking of blogging about was the thought of augmenting Enhanced Gravity Tractor EGT asteroid deflection with in-situ derived propellants.

The gravitation attraction force is usually the bottleneck in how fast you can do an asteroid deflection, but in some situations the propellant load might matter too.

That would imply getting somewhere between 16x the thrust per unit time as running the same amount of power through the HET. One nice thing is that some of this material can be gathered while landing to gather the additional mass for the enhanced gravity tractor.

Field-emission electric propulsion , a type of Colloid thruster. They typically use caesium or indium as the propellant due to their high atomic weights, low ionization potentials and low melting points. This ion rocket accelerates ions using the electric potential maintained between a cylindrical anode and negatively charged plasma which forms the cathode.

To start the engine, the anode on the upstream end is charged to a positive potential by a power supply. Simultaneously, a hollow cathode at the downstream end generates electrons. As the electrons move upstream toward the anode, an electromagnetic field traps them into a circling ring at the downstream end. This gyrating flow of electrons, called the Hall current, gives the Hall thruster its name.

The Hall current collides with a stream of magnesium propellant, creating ions. As magnesium ions are generated, they experience the electric field between the anode positive and the ring of electrons negative and exit as an accelerated ion beam.

A significant portion of the energy required to run the Hall Effect thruster is used to ionize the propellant, creating frozen flow losses. On the plus side, the electrons in the Hall current keep the plasma substantially neutral, allowing far greater thrust densities than other ion drives. Gridded Electrostatic Ion Thruster. Potassium seeded argon is ionized and the ions are accelerated electrostatically by electrodes. Other propellants can be used, such as cesium and buckyballs.

Though it has admirably high exhaust velocity, there are theoretical limits that ensure all Ion drives are low thrust. It also shares the same problem as the other electrically powered low-thrust drives. In the words of a NASA engineer the problem is "we can't make an extension cord long enough. Low powered ion drives can get by with solar power arrays, all ion drive space probes that exist in the real world use that system. Researchers are looking into beamed power systems, where the ion drive on the spaceship is energized by a laser beam from a remote space station.

And it suffers from the same critical thrust-limiting problem as any other ion engine: Which means that it has a net space charge which repels any additional ions trying to get in until the ones already under acceleration manage to get out, thus choking the propellant flow through the thruster. The upper limit on thrust is proportional to the cross-sectional area of the acceleration region and the square of the voltage gradient across the acceleration region, and even the most optimistic plausible values i.

You can only increase particle energy so much; you then start to get vacuum arcing across the acceleration chamber due to the enormous potential difference involved. So you can't keep pumping up the voltage indefinitely. To get higher thrust, you need to throw more particles into the mix. The more you do this, the more it will reduce the energy delivered to each particle.

The illustrated design uses a combination of microwaves and spinning magnets to ionize the propellant, eliminating the need for electrodes, which are susceptible to erosion in the ion stream.

The propellant is any metal that can be easily ionized and charge-separated. A suitable choice is magnesium, which is common in asteroids that were once part of the mantles of shattered parent bodies, and which volatilizes out of regolith at the relatively low temperature of K. The ion drive accelerates magnesium ions using a negatively charged grid, and neutralizes them as they exit.

The grids are made of C-C, to reduce erosion. Since the stream is composed of ions that are mutually repelling, the propellant flow is limited to low values proportional to the cross-sectional area of the acceleration region and the square root of the voltage gradient. A 60 MWe system with a thrust of 1. Colloids charged sub-micron droplets of a conducting non-metallic fluid are more massive than ions, allowing increased thrust at the expense of fuel economy.

This fictional ship is a species of Ion drive utilizing cadmium and powered by deuterium fusion. Looking at its performance I suspect that in reality no Ion drive could have such a high thrust. The back of my envelope says that you'd need one thousand ultimate Ion drives to get this much thrust. A working fluid such as hydrogen can be heated to 12, K by an electric arc. Since the temperatures imparted are not limited by the melting point of tungsten, as they are in a sold core electrothermal engine such as a resistojet, the arcjet can burn four times as hot.

However, the thoriated tungsten electrodes must be periodically replaced. When used for mining beneficiation, regolith or ore is initially processed with a 1 Tesla magnetic separator and impact grinder 3. The arcjet can also be used for arc welding.

This device works by generating microwaves in a cylindrical resonant, propellant-filled cavity, thereby inducing a plasma discharge through electromagnetic coupling. The discharge performs either mining or thrusting functions. In its mining capacity, the head brings to bear focused energy, tuned at close quarters by the local microwave guides, to a variety of frequencies designed to resonate and shatter particular minerals or ice. In its electrothermal thruster MET capacity, the microwave-sustained plasma superheats water, which is then thermodynamically expanded through a magnetic nozzle to create thrust.

The MET needs no electrodes to produce the microwaves, which allows the use of water propellant the oxygen atoms in a steam discharge would quickly dissolve electrodes. MET steamers can reach seconds of specific impulse due to the high K discharge source temperatures, augmented by rapid hydrogen-oxygen recombination in the nozzle. Vortex stabilization produces a well-defined axisymmetric flow. The illustration shows a microwave plasma discharge created by tuning the TM mode for impedance-matched operation.

Regenerative water cooling is used throughout. For pressures of 45 atm, each unit can produce 30 N of thrust. The thrust array contains such units, at 50 kg each. Power and Randall A. Chapman, Lewis Research Center, In a resistojet , propellant flows over a resistance-wire heating element much like a space heater or toaster then the heated propellant escapes out the exhaust nozzle.

They are mostly used as attitude jets on satellites, and in situations where energy is more plentiful than mass. Tungsten, the metal with the highest melting point K , may be used to electric-resistance heat ore for smelting or propellant for thrusting. In the latter mode, the resistojet is an electro-thermal rocket that has a specific impulse of 1 ksec using hydrogen heated to K. Internal pressures are 0. To reduce ohmic losses, the heat exchanger uses a high voltage 10 kV low current Once arrived at a mining site, the tungsten elements, together with wall of ceramic lego-blocks produced in-situ from regolith by magma electrolysis are used to build an electric furnace.

Tungsten resistance-heated furnaces are essential in steel-making. They are used to sand cast slabs of iron from fines magnetically separated from regolith , refine iron into steel using carbon imported from Type C asteroids , and remove silicon and sulfur impurities using CaAl 2 O 4 flux roasted from lunar highland regolith.

An e-beam beam of electrons is a versatile tool. It can bore holes in solid rock mining , impart velocity to reaction mass rocketry , remove material in a computer numerical control cutter finished part fabrication , or act as a laser initiator free electron laser.

A wakefield electron accelerator uses a brief femtosecond laser pulse to strip electrons from gas atoms and to shove them ahead. Other electrons entering the electron-depleted zone create a repulsive electrostatic force. The initial tight grouping of electrons effectively surf on the electrostatic wave.

Wakefield accelerators a few meters long exhibit the same acceleration as a conventional rf accelerator kilometers in length. In a million-volt-plus electron beam the electrons are approaching lightspeed, so the term relativistic electron beam is appropriate. The wakefield can be used as an electrothermal rocket similar in principle to the arcjet, but far less discriminating in its choice of propellant. Fusion propulsion uses the awesome might of nuclear fusion instead of nuclear fission or chemical power.

They burn fusion fuels , and for reaction mass use either the fusion reaction products or cold propellant heated by the fusion energy. There is a discussion of magnetic nozzles here. For one thing, forget muon catalyzed fusion.

The temperature of the exhaust will not be high enough for torch ship like performance. You might use a heavy ion beam driven inertial confinement fusion pulse drive , or a Z-pinch fusion pulse drive. I don't think magnetic confinement fusion will work — you are dealing with a such high power levels I don't think you want to try confining this inside your spacecraft because it would melt.

D-T deuterium-tritium fusion is not very good for this purpose. If we assume we need to keep the temperature of the drive machinery below K to keep iron from melting, or diamond components from turning into graphite , you would need all non-expendable drive components to be located at least meters away from the point where the fusion pulses go off.

For a terawatt torch, this means you need to deal with gigawatts of radiation. You need a meter radius bell for your drive system to keep the temperature down.

This lets you get away with a 66 meter radius bell for a terawatt torch. To minimize the amount of x-rays emitted, you need to run the reaction at keV per particle, or 1. If it is hotter or colder, you get more x-rays radiated and more heat to deal with.

This could provide 1 G of acceleration to a spacecraft with a mass of at most 26, kg, or If we say we have a payload of 20 metric tons and the rest is propellant, you have 50 hours of acceleration at maximum thrust. Note that this is insufficient to run a 1 G brachistochrone. Burn at the beginning for a transfer orbit, then burn at the end to brake at your destination.

Note that thrust and rate of propellant flow scales linearly with drive power, while the required bell radius scales as the square root of the drive power.

If you use active cooling, with fluid filled heat pipes pumping the heat away to radiators, you could reduce the size of the drive bell somewhat, maybe by a factor of two or three. Also note that the propellant mass flow is quite insufficient for open cycle cooling as you proposed in an earlier post in this thread. Due to the nature of fusion torch drives, your small ships may be sitting on the end of a large volume drive assembly. The drive does not have to be solid — it could be a filigree of magnetic coils and beam directing machinery for the heavy ion beams, plus a fuel pellet gun.

The ion beams zap the pellet from far away when it has drifted to the center of the drive assembly, and the magnetic fields direct the hot fusion plasma out the back for thrust. One gigawatt of power requires burning a mere 0. Note that Tritium has an exceedingly short half-life of Use it or lose it. Most designs using Tritium included a blanket of Lithium to breed more fresh Tritium fuel. Fuel is Hydrogen and Boron Bombard Boron atoms with Protons i. Current research indicatates that there may be some neutrons.

Paul Dietz says there are two nasty side reactions. One makes a Carbon atom and a gamma ray, the other makes a Nitrogen atom and a neutron. The first side reaction is quite a bit less likely than the desired reaction, but gamma rays are harmful and quite penetrating. The second side reaction occurs with secondary alpha particles before they are thermalized.

The Hydrogen - Boron reaction is sometimes termed "thermonuclear fission " as opposed to the more common "thermonuclear fusion". A pity about the low thrust. The fusion drives in Larry Niven's "Known Space" novels probably have performance similar to H-B Fusion, but with millions of newtons of thrust.

The catch is, you have to arrange for the protons to impact with keV of energy, and even then the reaction cross section is fairly small. Shoot a keV proton beam through a cloud of boron plasma, and most of the protons will just shoot right through.

Either way, you won't likely get enough energy from the few which fuse to pay for accelerating all the ones which didn't. Now, a dense p-B plasma at a temperature of keV is another matter. With everything bouncing around at about the right energy, sooner or later everything will fuse. But containing such a dense, hot plasma for any reasonable length of time, is well beyond the current state of the art.

We're still working on 25 keV plasmas for D-T fusion. If you could make it work with reasonable efficiency, you'd get on the order of ten gigawatt-hours of usable power per kilogram of fuel. Graduate Student Alex H. Cheung is looking into turning this concept into a propulsion system. Fuel is helium 3 and deuterium. There are five general methods for confining plasmas long enough and hot enough for achieving a positive Q more energy out of a reaction than you need to ignite it, "break even":.

Of these reactions, the fusion of deuterium and tritium D-T , has the lowest ignition temperature 40 million degrees K, or 5. Another disadvantage is that 3 He is so rare that , tonnes of regolith scavenging would be needed to obtain a kilogram of it.

Alternatively, helium 3 can be scooped from the atmospheres of Jupiter or Saturn. Deuterium, in contrast, is abundant and cheap. Its advantage is that is suffers no side reactions and emits no neutrons, and hence the reactor components do not become radioactive. The 6 Li-H reaction is similarly clean. However, both the H-B and 6 Li-H reactions run hot, and thus ion-electron collisions in the plasma cause high bremsstrahllung x-ray losses to the reactor first wall.

There are two types of mission.

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