NASA Wants Green Rocket Fuel 185
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."
NOFB (Score:5, Informative)
Nitrous oxide fuel blend [wikipedia.org] 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 [wordpress.com]. He think's it's a game changer.
CFCs got hard to obtain (Score:5, Informative)
Re:CFCs got hard to obtain (Score:4, Informative)
Re:God help us (Score:5, Informative)
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.
Hydrogen peroxide (Score:5, Informative)
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."
Re:CFCs got hard to obtain (Score:5, Informative)
Err, no it's not
Re:God help us (Score:3, Informative)
Ummm, hydrazine is not a monopropellant, it is "burned" with an oxidiser such as nitrogen tetroxide (N2O4) or an acid like Red Fuming Nitric Acid (RFNA) which, as you can guess from the name has the same sort of ground handling properties as hydrazine (i.e. if it leaks it can dissolve the operators working the fuelling system).
The Space Shuttle's Orbital Manoeuvering System (OMS) engines burned monomethyl hydrazine (MMH) and N2O4. This meant that when the Shuttle returned to Earth it had to be effectively treated as toxic waste before handlers could safely remove the surplus fuel in the OMS tanks. If you ever watch videos of a Shuttle landing and its aftermath you'll see folks in full-coverage bunnysuits at the back of the Shuttle making sure no propellants are leaking and preparing to decant the reserve fuel and oxidiser from the tanks before the Shuttle is moved off the runway.
A major benefit of fuel/oxidiser combos like MMH/N2O4 is that they are very stable and stay liquid at very low temps, something that long-duration space flights require. The Cassini mission probe carried over three tonnes of MMH/N2O4 and it spent seven years in flight before its final 90-minute engine burn to successfully put the probe into orbit around Saturn.
Re:I take it you're not a technician handling it? (Score:5, Informative)
We can handle it safely but it comes at a cost. Here are some examples.
We need to wear these things. http://www.wolfhazmat.de/astrosuit/nasa_01.htm [wolfhazmat.de].
Every time you run an operation where it might spill you need to clear the work area of all nonessential personnel.
You need scrubbers to vent the vapors through when processing.
You need detectors/absorbers on every port.
You need yearly training for the whole workforce to know what to do when there is a leak (there is a VERY distinctive ammonia smell)
So the main thing isn't that it's unsafe. We know how to work with it properly. The problem is the costs involved with doing it. If an alternative can be found it would make it much safer and quicker to process rockets and spacecraft. Imagine if you had to have a 500 ft clear area around an airplane while fueling it. It would make everything about flying more expensive.
Re:God help us (Score:5, Informative)
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. :)
Re:God help us (Score:5, Informative)
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 [nasa.gov]
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 [mediamatters.org]
Re:God help us (Score:5, Informative)
Re:We don't launch enough rockets for this to matt (Score:5, Informative)
Re:From the introduction (Score:4, Informative)
Tidied up the quote a bit, since it's delectable:
Now it is clear that anyone working with rocket fuels is outstandingly mad. I don't mean garden-variety crazy or a merely raving lunatic. I mean a record-shattering exponent of far-out insanity.
There are, after all, some chemicals that explode shatteringly, some that flame ravenously, some that corrode hellishly, some that poison sneakily, and some that stink stenchily. As far as I know, though, only liquid rocket fuels have all these delightful properties combined into one delectable whole.
Also, I'd like to also state my thanks to imbaczek for posting the link, 40 pages in and it's a page-turner :)
Re:God help us (Score:5, Informative)
"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." [mikeroweworks.com] 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.)
Re:God help us (Score:5, Informative)
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.
Re:We don't launch enough rockets for this to matt (Score:5, Informative)
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.