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NASA Wants Green Rocket Fuel
coondoggie writes "NASA is looking for technology that could offer green rocket fuel alternatives to the highly toxic fuel hydrazine used to fire up most rockets today. According to NASA: 'Hydrazine is an efficient and ubiquitous propellant that can be stored for long periods of time, but is also highly corrosive and toxic.' It is used extensively on commercial and defense department satellites as well as for NASA science and exploration missions."
Everybody should read one book about rocket propellants: Ignition! by John D. Clark. Apart from it being a good (and hilarious at times) read, it'll also show you why this project will most likely end up being a waste of money.
Nitrous oxide fuel blend is a mixed mono propellent that's non-toxic and has 320-340s ISP. Max Vozoff, formerly of SpaceX, talks about NOFB in this episode of The Space Show. He think's it's a game changer.
I guess if I was one of the technical crew who had to work with this stuff and be exposed to its toxicity, I'd be welcoming my boss researching a way of making my life safer. I'm sure the technicians love working for NASA but given the choice between working with highly toxic fuels that might burn them/ give them cancer/ other nice side effect, or something less damaging, I am sure they'd be all in favour of an option that won't harm them and won't potentially leak into local water tables, get drawn up into local water supply / agriculture and end up in their kids.
My experience is the people most likely to moan about health and safety are those whose greatest risk of an industrial injury is stabbing themselves with the office stapler. Folk working in genuinely high risk environments seem quite grateful their bosses have to abide by regulations.
I don't know if you've ever tried to obtain Halon lately but you'll find even if your system is still grandfathered it's nigh on impossible to get hold of, they've pretty much stopped making it. It's the same with the CFC's used by the shuttle's foam, being allowed to make it didn't mean the raw components are easy to come by. If they'd wanted to continue using CFCs they'd have to had to pay for a supply line to be available and maintained, whether they needed a lot or a little. The problem wasn't that they went green, the problem was that the alternative they chose wasn't the right one and they didn't want to invest the time and money working around that properly.
Going Green is probably just an excuse here, it's the money. Because it's toxic and corrosive it's hard to handle and thus expensive to handle. First you have the expensive equipment and protective gear, and then we have the paperwork... Think about it this way, every time you use the stuff you're generating reams and reams of risk assessments and paperwork. That paperwork is essentially a writeonly document which has to be produced everytime they come up with a slightly different way to do things.
Hydrazine is described as corrosive and toxic, both of which will make it expensive to handle, require special pipes and tanks and so on. As far as I know, it's not
an environmental consideration -- it surely decays to nitrogen and water pretty fast.
I suspect this is about cost saving in the handling.
It's not really about being "Green". Hydrazine is very toxic and extremely unstable. It's terribly dangerous to work with even when things are going right, and when a launch goes wrong you may end up dropping a hydrazine-filled satellite in an urban area. That's not good, so you have to considerably overengineer the tanks (adding weight, reducing payload) so they'll survive reentry and not poison people.
So why do we use this devil of a propellant?
Normal rocket juice is two parts - fuel (eg H2, kerosene) and oxidizer (eg O2, N20). You flow both into your combustion chamber, strike a spark, and away you go. That's great for long sessions of high-power lift. The problem is it's terrible for fine maneuvering. Maintaining the proper mixture gets harder with small flows, your spark plugs wear out with repeated firings, and generally the whole bipropellant setup is big, heavy, and complicated, and you want your satellite to be compact, light, and as simple as possible for reliability.
So that's where hydrazine comes in. It's the same property that makes it dangerously unstable that makes it an ideal fuel when you need very low impulse and very high reliability. You just open a small valve on the line from the pressurized tank tank to the engine - that's your only moving part. The hydrazine flows into the combustion chamber where there's a catalyst. It instantly and very exothermically decomposes into ammonia, nitrogen and hydrogen gas. The very high temperature rise makes the exhaust velocity really high, which is great for efficiency.
Et voila, you have a rocket engine where the only moving part is the flow control valve. Since you want to do complex maneuvers, you can sprinkle a bunch of these little, simple, lightweight engines all over your craft instead of having a couple big complex (fuel mixing) ones with vectoring (gimbals and actuators are just more things to fail, plus now you need flexible fuel lines), and you can do your maneuvers in tiny bursts that are too short to even get a bipropellant engine to light off.
Similarly, the very low parts count makes hydrazine turbine engines very useful where maximum reliability is required - for instance APUs for hydraulic power used for the space shuttle, and on military aircraft for emergency backups.
Finding a safe replacement would allow much safer handling, lighter safety systems, and allow monopropellant engines to be used in places that they're impractical now.
When I was at school, one of the exam questions in S level chemistry was to estimate the maximum temperature reached if a stream of hydrazine hydrate was mixed with a stream of concentrated hydrogen peroxide. Of course, after the exam we had to try it... two carefully aimed pipettes over the centre of the biggest Belfast sink in the lab, three quarters full of cold water. I'm not disclosing how we released the liquids safely. If you can work it out, I'm not telling you anything you don't already know here. There was a white glow at the centre. I guess nowadays with the fear of terrorists no school exam would dare ask the question, whereas in those days I suspect the exam setter thought "Well, if they've done the work for S level, they deserve a little entertainment."
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
Politician storage is complex, expensive, and requires high levels of administratium, the heaviest element known. After long periods of storage politicians also decay into bureaucratium, which has a negative half-life and so becomes more massive over time.
Wikipedia says:
Hydrazine is also used as a low-power monopropellant for the maneuvering thrusters of spacecraft, and the Space Shuttle's auxiliary power units (APUs). In addition, monopropellant hydrazine-fueled rocket engines are often used in terminal descent of spacecraft. A collection of such engines was used in both Viking program landers as well as the Phoenix lander launched in August 2007.
In all hydrazine monopropellant engines, the hydrazine is passed by a catalyst such as iridium metal supported by high-surface-area alumina (aluminium oxide) or carbon nanofibers,[25] or more recently molybdenum nitride on alumina,[26] which causes it to decompose into ammonia, nitrogen gas, and hydrogen gas according to the following reactions:
Countercitation needed. :)
Before you spout off about the ET insulation foam having been reformulated without CFCs, try reading the CAIB report (volume 1, Page 51), which specifically states that the portion of the foam that broke loose was the OLD CFC-based formulation.
http://caib.nasa.gov/news/report/pdf/vol1/full/caib_report_volume1.pdf
The story about the reformulated foam causing the Columbia accident is largely the doing of Rush Limbaugh, who seized on a lie from one of his typically ill-informed listeners, and kept repeating it until it became accepted as fact by everyone on the right.
http://mediamatters.org/research/200508090007
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Hydrazine isn't used for heavy lifting rockets. It's for monopropellant thrusters. Satellite positioning, lifting and attitude control. The shuttle manouvering thrusters (Until recent retirement). That sort of thing. Very important in moving satellites around once they are up there.
Challenger blew up because one of the O-ring seals failed in a SRB due to an unexpected susceptability to prolonged low-temperature conditions. Nothing to do with asbestos.
Doesn't it happen to be the propellant for the Dragon's thrusters -- used for launch escape, orbital maneuvering, attitude control, and perhaps even controlled descent. I don't see that last one panning out all that well: you probably don't want to step out from a Dragon capsule right after it touched down on Earth and breathe the fumes. There's always a bit of unburned stuff around, and it doesn't take much to make you sick AFAIK. Space Shuttle is a much bigger vehicle so it can support you hanging around until it's safe to egress -- just listen to NASA TV recordings from Shuttle landings and hear how long they stay after landing, doing checklists... On a Dragon there would be not much to do, and I don't know how much oxygen is left in the Spacecraft segment after landing -- i.e. how long can you stay put before popping the hatch; especially in emergency situations -- say somehow they blow a tank a-la Apollo 13 and need to get back ASAP, it'd be a sad thing to land safely just to get killed by hydrazine vapors... I'm sure they are considering all that, but it'd be interesting to read some documents giving a bit more detail to the procedures...
A successful API design takes a mixture of software design and pedagogy.
Even more important - a hydrazine thruster is super-high-reliability. In space, pulling to the curb and calling AAA isn't an option (yet.) A liquid bi-propellant thruster is substantially more complicated than a hydrazine monopropellant one, and is more likely to have problems.
"Green" is the modern equivalent of "Safety First," which is a load of crap except for the safety alarmists (i.e. safety equipment vendors.) Mike Rowe is spot on with "Safety Third." I'd put Green at fourth. Every task has an attendant risk and cost. Environmental impact is a cost.
I'm all for developing less-toxic solutions, but a hydrazine monopropellant thruster is damned effective. It also shifts the system risk to the ground handling crews, where we can deal with it (as opposed to shifting it to on-orbit failures.)
"Kerosene + LOx = OMFG that is a LOT of Thrust!"
Yes but you can't store LOX for long periods, It want's to boil off. Hydrazine will stay stable for a long time, and another important aspect of hydrazine is it's hypergolic properties. This makes the engines very very reliable and simple to build. Just mix hydrazine and nitrogen tetroxide in a combustion chamber and it auto ignites. Or you can use a catalyst to break down the hydrazine, like in the shuttle APU. I know of no "green" propellents that can do this.
The "EPA asbestos ban caused Challenger!" story is every bit as much BS as the "CFC-free foam caused Columbia!" story. The material used on Challenger still contained asbestos, just as the failed foam on Columbia's fuel tank was made with CFCs. Read James Oberg's explamation here:
www.msnbc.msn.com/id/11031097/ns/technology_and_science-space/t/myths-about-challenger-shuttle-disaster
Myth #5: Environmental ban led to weaker sealant
A favorite of the Internet, this myth states that a major factor in the disaster was that NASA had been ordered by regulatory agencies to abandon a working pressure sealant because it contained too much asbestos, and use a weaker replacement. But the replacement of the seal was unrelated to the disaster â" and occurred prior to any environmental ban.
Even the original putty had persistent sealing problems, and after it was replaced by another putty that also contained asbestos, the higher level of breaches was connected not to the putty itself, but to a new test procedure being used. âoeWe discovered that it was this leak check which was a likely cause of the dangerous bubbles in the putty that I had heard about," wrote physicist Richard Feynman, a member of the Challenger investigation board.
And the bubble effect was unconnected with the actual seal violation that would ultimately doom Challenger and its crew. The cause was an inadequate low-temperature performance of the O-ring seal itself, which had not been replaced.
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