What are Hypergolic Rocket Fuels? (Other than Explosive, Corrosive, Toxic, Carcinogenic and Orange)
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- čas přidán 7. 11. 2019
- Hypergolic fuels are a core technology in rocket science, propellents that will spontaneously combust when mixed together. This makes them attractive for rocket designers, who generally aren't the people who have to get in a the protective gear to load the stuff.
So, what are they made of, and why do designers pick one option over another? - Věda a technologie
Hypergolic fuels: Booms, Bangs and Bottles full of Nope since 1935.
You should be writing my titles.
"Bottles of nope"
Absolutely priceless
With all the things about these hypergolics, they are still the least dangerous ones that are in use, the more exotic ones proved to be a little hard to handle, so the ones that merely dissolve you are the ones in use.
@@scottmanley gotta be worth an edit..
A few more lyrics and this could be sung in the manner of a sea shanty. I'll leave it to more loquacious minds.
“Ignition!” occupies a special place in my library.
Defiantly. There is a special shelf for special books. its the only one not stuffed. I build more shelves rather than add an unworthy book to that shelf.
NMCCW I am 40 pages into it and can’t seem to put it down! So far it is one of my favorite scientific books due to the sarcasm and humor used throughout the book.
Same. It's a gem.
Does anyone else kinda feel like sometimes when Scott says "fly safe" its almost like a threat or ominous advice that a supervillian will give?
He really likes his flies.
Not in the least.
No. He’s like the nicest guy
This one was particularly sinister.
His subject brought a pretty grim warning out of him this time.
ah Aerozine 50, the Arnold Palmer of hypergolics
As Derek Lowe once wrote in his 'Things I Won't Work With' column, "There aren't many gently sloping paths down to nitrogen gas."
Things I Won't Work With is pure writing genius, comparable only with Ignition in its wit, truth and brain-melting terror at what chemists will do. The FOOF article in particular makes me cringe every time.
That's a great way to put it!
I've been a fan of Lowe's for some time. "Sand Won't Save You This time" is a classic. ClF3 provides you with the fun of seeing house bricks and snow burst into flames. Tasty. Oh, by the way, the guy who worked on FOOF, Alexander Streng (aided by his wife - now that's serious love when you're prepared to help your husband work with FOOF) also came up with O2ClF3, the world's only violet coloured oxidising agent. While permanganate has a reddish bias to its purple colour, O2ClF3 is far end of the spectrum violet, even more so than subliming iodine.
As for the Strengs, Lucia Streng was also a hardcore chemist in her own right. She was the one who synthesised krypton difluoride. Oh to have been a fly on the wall during their dinner time conversations!
@@throx ... if you can get a copy of the Streng paper on FOOF, do so. It's hilarious to behold. Mind-buggering chemical insanity, presented in the sort of calm, understated tones more usually associated with discussion of Greek noun declensions. I found a copy, and boy, did this guy know how to make mad science look frighteningly reasonable. The epic level of nonchalance that exudes from the paper, while discussing the sort of chemical reactions that make most sensible people want to be on a different continental land mass, simply has to be seen.
@@Calilasseia I wonder if they made O2ClF3 as a quest to create a pretty colour for each other. The oxidation may be a side effect of aiming for specific electron binding levels to get the desired spectral lines.
When the chemical you're using to make your propellant safer is ***hydrofluoric acid***, that's a rocket fuel I'll take with a tall glass of nope!
Less evaporation during transport/storage.👍
If you think that's bad, you should check out chlorine tri-fluoride. It will spontaneously combust on contact with _sand._ In other words, there is no possible way to extinguish a chlorine tri-fluoride fire.
@@deusexaethera let it burn out. or dose it with water for a show.
@@deusexaethera The most fun fuel/oxidizer combination for a rocket: chlorine trifluoride and dimethylmercury. Great ISP, at the price of turning your launch pad into a Superfund site, _at best_!!!
meldroc whats the isp?
"Oh no, we spilled some liquid oxygen! What do we do?"
"Shut off any ignition sources and leave the area. Just wait it out."
Back When, one of the engineers habitually smoked some kind of old jockstrap/inner tube mix cigars. One of the techs dipped one of these in LOX and left it on the his desk for the engineer to find. When he lit it, it flashed instantly to ash, and took a goodly part of his mustache and eyebrows with it. He took the hint...
@@Jonascord Did the same, they burn really fast, he got a single puff out of it before it was down to the filter.
With LOX remember not to use shoe polish, it may not be the best thing. Was filling a LOX tank in the bay, and there was a snake in there. Broke it, as it fell out of the gloves when I grabbed it, and on landing on the floor at cryogenic temperature it broke into pieces.
Check and see if your feet are still there. You would have learned real fast if the ground was fuel contaminated.
@@Jonascord I'm wondering who was he employed by the propulsion engineering division of Acme?
@@arnoldsherrill6305 Next Best thing, Lockheed.
I loved this video. It reminded me of the time way back when I was a kid when I was playing with some friends and we accidentally made a hypergolic mixture. Some other kids had raided a chemical storage building and we had gallon jars of reagent grade acid in just about every basic variety. Quarter of a small test tube filled with nitric acid and other "stuff" went boom. Burned a hole in the ceiling and through one kid's coat giving him the nastiest big green scab. We did a little research and figured out we'd accidentally made rocket fuel, but I had forgot about that until watching the fuming nitric acid in this video. Damn, I had a good childhood.
i'll bet that kid didn't have a good childhood
Ok, boomer
Ah back when home chemistry sets for kids were still thought of as a perfectly normal idea.
I once made a batch of acid (Not sure what kind as this was in the late 80's) knocked the beaker over by accident after dissolving my mixing stick, and subsequently melted a hole in my bedroom carpet. Dad moved a wardrobe over the hole after cleaning up and taking away my chemistry set. That hole might still be there :-)
I wish people could still have childhoods like this
You sure did. We did :)
"Scott Manley, the hypergolucky guy!" (From "happy-go-lucky", in case you've never heard the term before!)
Excellent video as always, Scott, thanks!
If you have to wear a space suit _on Earth_ the design of your spacecraft may need rethinking.
I've been reading Ignition! myself recently. Thank you for recommending it! It's a fantastic book!
I'm a fan of the British Black Arrow's sort-of hypergolic system using the heat (600F) from decomposing H2O2 to auto-ignite the RP-1.
Wrote out a long comment on the Me163 and of course you covered it! What an absolutely insane machine. Used two fuels that when mixed they ignited... and the pilot sat in between the tanks in the wings, and right in front of the primitive, unstable rocket motor.
The Me163 had to be refuelled from two separate trucks that had to stay far away from each other to prevent even the fumes from mixing. One drop in the wrong place, any unnoticed spill before the other fuel was loaded, and BOOM. (One fuel type per wing, they couldn't touch before reaching the rocket motor).
You had to be a real mad lad to be on the ground crew, and clinically insane to be the pilot.
German test pilot Hanna Reitsch loved that little Aircraft .I think one tried to kill her ?
Hanna Reitsch crashed several times in the 163, still loved it. If you don't mind it being a flying bomb, especially for the time, it is a brilliant machine.
Were German test pilots even allowed to say no to a test flight?
Rock Lover She lost her nose when the 163 crashed. She would only wear a lap strap not a full harness, she smashed into the dashboard.
The BBC TV series “The Secret War” has a great episode with the 163 and interviews with Hannah Reitsch.
As a chemist, love these chemistry videos! When I watched that Boeing launch abort test I recognised the gas as NO2, glad you're here to explain how that came about because I was wondering!
One small point - be careful how you use the terms "strong acid" and "weak acid" because although HF is very reactive it is not technically a strong acid. Strong acids are defined as acids that completely dissociate in water and HF does not because the bond is stronger and has more covalency due to better orbital overlap.
Further to that, the 1% HF you're talking about is described as a dilute acid because a weak acid is defined as an acid that does not fully dissociate in water.
Using HF to protect the rocket plumbing from acid is like using Sodium Fluoride to protect teeth from acid, just a lot more extreme.
An odd thing is, it's not really a terribly strong acid; the fluorine wants to hold onto the hydrogen too much. It is really toxic, as are many of the byproducts when it reacts with random molecules, and it particularly attacks skin and glass.
Great explanation, Scott!
And thanks to all the commenters who suggested John D. Clark's _Ignition!_
I just bought it for my Kindle, and Asimov's Foreword had me laughing out loud!
I own the books “The Chemical Elements and Their Compounds” by Neville Sidgewick in 1950. I remember the part about perchloric esters and enjoyed the bit in Ignition! where the author refers to perchloric esters and draws attention to the Sidgewick work and how experimenters wore iron masks.
This reminds me of an incident that happened some time back in the 90's when I worked at Rocketdyne in Canoga Park. Two scientists were killed in an explosion when they mixed some chemicals together. I don't know what they were mixing, but the initial story was that they were doing rocket fuel research. Later, the truth came out; they were actually illegally disposing of hazardous chemicals by combustion, and the company used "research" as an excuse to get around environmental laws. This happened at the Santa Suzanna Field Laboratory, which we called "the hill".
In the Army we had to deal with a lance missile that had malfunctioned. It used UDMH and IRFNA. Both were a bitch because they could compromise the filters in a gas mask and then melt your lungs. We had to use full rubber tap suits with self contained breathing systems just to approach the missile. Then we had to render safe the damaged warhead and retrieve the telemetry package. This was probably the most dangerous thing I did.
9:32 - and that's how Scott Manley told North Korea what they were doing wrong...
For additional government secrets, look at the recent history of this channel. Scott has been posting some seriously "Should this maybe be classified or something" types of videos lately.
It isn't classified, but the things he shares are so cool that you think they should be!
Scott said they moved on
We already have a "clean" hypergolic oxidizer. The jetpack they used at the Olympics used it as a monopropellant. It's Hydrogen Peroxide, and at a high enough purity (over 80%) it is referred to as High Test Peroxide, or HTP.
Very suitable as a rocket fuel oxidizer.
Problem is, it's not nice stuff to handle, and it's not long-term stable.
The hydrogen peroxide you can buy in the drug store is 3-5% peroxide with the rest being water.
Hair-bleach grade peroxide is 10%, and you don't want to spill that on you by accident.
Peroxide you find in a chemistry lab supply catalog is commonly available up to 30% concentration, and if you get that on you you'll get a chemical burn.
The rocket grade stuff is potent enough to eat the flesh off of your bones quite rapidly.
On the bright side, hydrogen peroxide is not stable enough to be poisonous or carcinogenic, and many plants and animals have enzymes specifically to deal with decomposing hydrogen peroxide (so called Peroxidase enzymes).
The primary problem with HTP is it's stability, or more correctly it's lack of long-term stability. Hydrogen peroxide at any concentration will spontaneously decompose to water and oxygen gas without the presence of a catalyst, so every vessel that is expected to store hydrogen peroxide has some form of pressure-relief valve or pressure accommodating features in it as a safety measure. Hydrogen peroxide is commonly stored in plastic bottles with the top section having a bellows or accordion shape, specifically so the oxygen that forms when hydrogen peroxide decomposes has somewhere to go without making the bottle explode.
Britain used peroxide in many rocket engines with RP-1, and that combination might as well be hypergolic. Sure, it's not RELIABLY "ignites on contact" hypergolic, but if the peroxide is decomposed by running it thru a catalyst bed the resulting reaction products (water vapor and oxygen gas) exit the catalyst bed at a high enough temperature to ignite the RP-1, which will burn using the oxygen liberated from the peroxide, so you still get the end result of ditching the ignition system (unless you count the catalyst bed, however I don't count that because it's in constant operation while the engine is firing).
With a similar approach, pretty much any standard non-hypergolic rocket fuel will work with HTP.
I believe that combining HTP with one of these new green monopropellants would result in a green bipropellant, however I have no idea if anyone has investigated this.
The reason hydrogen peroxide is not used for rocket oxidizer much today is that it has poor specific impulse. With the same fuel, Liquid Oxygen will provide superior specific impulse compared to H2O2 as you don't have to lug around all that water that can't react with the fuel. When a storeable propellant is needed, UDMH/NTO is preferred because it gives superior performance, however I do believe that there have been rocket engines that used the hypergolic combination of a hydrazine-type fuel and H2O2.
We tend to think of hypergolics as highly reactive fuels which ignite upon contact with highly reactive oxidizers, but then there is chlorine trifluoride which is hypergolic with rocket engines, rocket scientists and rocket launch pads...
Back in the early 1970's I worked for a watchmaker/jeweler who used fuming nitric acid to clean silver, he would put a little on cotton wool and then wipe the silver with it.He said it spread the silver about,one thing for certain it always gave him sore fingers as he never wore gloves and by the next day was complaining about not being able to work as his fingers were sore. He never learnt I said on many occasions he should wear gloves.
Smelly too, in the case of aniline.
Edit: And no love for Britain's RP-1/HTP engines?
If you decompose the H2O2, the oxygen and steam are hot enought to be hypergolic with kerosene.
Mhmm. Stink rockets!
Your lungs wants to know your location...
Made me think of bombardier beetles. Sadly I couldnt find anything about the specific impulse of their butt explosions on wikipedia.
They tried things that were far more smelly than aniline... get a copy of "Ignition!", there's a whole chapter titled, "The Hunting of the Hypergol", describing all the crazy things they tried out in the decade after WW2.
@@WakarimasenKa Don't think it is much, more designed to leave them right there, while the aggressor is desperately wanting to be NOT there.
Thanks again Scott.. I always wondered about fuels and their properties.. Great class.. I even took notes.. carry on, be safe and have fun doing it!
Missed these types of videos from Scott lately. Happy it’s back.
Your video about propellants inspired me to start reading "Ignition!", and I literally read the chapter you just covered today!
Starting the weekend with Scott Manley!
Yes, after dealing with all the BS in the daily news, I look forward to some intelligent, factual content from Scott.
I wonder how many young people are inspired by this video to become chemists. Scott makes it interesting and walks you through what problems those chemists were solving
Thanks for covering red- and white-fuming nitric acid. Long ago, I read references to them, but no one ever explained what they were, and you couldn't find it even in specialty shops! The "fuming" part should have tipped me off.
Great as always Scott. I'm just finishing reading Ignition!: An Informal History of Liquid Rocket Propellants and absolutely love it. Fascinating read on the history of rocket fuels.
The lighting was great and audio better! Content was fantastic as always too :D
Top work!
I like the word "Hypergolic".
@@metalwhere that's why there are no vampire astronauts.
I initially thought it was hyper-gaullic, like a spiced up version of Asterix and Obelix.
Stop being hyperbolic.
But what does it mean?
@@aspuzling Explained here: 0:10
A lot of Europe is in a place right know where they would need someone from science instead of a politician.
Know that I've made my nephews watch these videos of yours and they want to learn so much more.
Yours sincerely iamthebeelzebub.
A lot of the world is in dire need of scientists, not just Europe. Look at the US, South America...
Same situation in the U.S. - I feel like we need intelligent content like this before someone outlaws it...
It's a good day when there's a new Scott Manley video!
Another great video Scott, always enjoy your content. Hope you have a good weekend!
That was a fantastic summary. This whole area of chemical engineering is pretty much a mystery to most other engineers. I had heard those propellant terms many times over the years without knowing what they really meant. THANKS!!
Get a limited edition HULLO-39 Kraken T-Shirt (or Hoodie) and help support the channel. www.bonfire.com/hullo-39/
Hey friend, you dropped an *h*
@@Mythricia1988 Obviously there were dark forces at work trying to stop this campaign.
The most amazing thing about the Hydrazines is that they figured out how to make them at all. as you say, Hydrazine tends to blow up at the drop of a hat. with a fairly high explosive velocity.
"The real name for Hydrazine is hard to say, but that's the least of your problems" lol
ANY other person or CZcamsr would require 1hour to explain it. Scott does the job in 11minutes with lots of it coming from his memory.
I'm betting he writes a script he's cribbing off of. Not a dig on him, he still has to do the work and put a lot of careful thought into what makes the cut. Succinctness is an underappreciated life skill.
@@JeepWranglerIslander he doesn't actually and that just shows that he is in fact a godly manifestation
Now this is great stuff. Nobody does rocket science like Scott Manley. Fabulous fuel talk about stuff I really wanted to know. In my job I use strong nitric fuming like this. Never knew about inhibitor system using HF. Golden man! Top drawer!
Scott - you’re very close to 300,000,000 views on CZcams. 🤯 Congratulations!! And thanks again for all the amazing content.... onwards to 1,000,000,000!! Fly safe!
One nice thing is that their mach diamonds look beautiful!
Thanks for the chemistry lesson Scott!
More of the same in the book "Ignition!" It's a fun book.
One of the handful of consistent channels where I don't feel less intelligent after watching a video, which is very much appreciated!
You didn't mention the nastiest oxidiser of them all: Chlorine Trifluoride
This stuff makes literally anything a hypergolic fuel.
That's what this video is all about
czcams.com/video/_wLk2j7_KB0/video.html
Chlorine Pentaflouride: all the nastiness of CTF, with 20 seconds better performance. :-)
Chlorine Trifluoride: everything is bomb.
@@drtidrow "At room temperature it reacts readily with all elements (including otherwise "inert" elements like platinum and gold)"
Sounds nasty.
@@JohnSmith-dt1tw ... In short ... Reacts with: baryonic matter. :D
Yess more stuff on hypergolics!!! Starting the weekend the right way!
Fascinating summary Scott, thanks!
Fascinating stuff! Thanks for this interesting summary! 🚀💥💨
My favourite video from this channel
I worked around the Titan II when I was in the USAF in the late 1960’s. Those propellant transfer guys didn’t fool around. If you haven’t seen “Command and Control,” the documentary about the time we almost had Armageddon in Arkansas, it is worth the time to watch.
Early congrats on 1M subs Scott, it won't be long now. Thanks for all of the great info on our space programs.
I'm not a chemistry expert, but I think "nitrogen tetroxide" should be a completely correct name. You can leave out the prefix when it's the "standard" mixture... mononitrogen tetroxide isn't really a thing as far as I can figure, so dinitrogen should be the correct default when you've got four oxygens.
Classic Intro, GREAT =)
Hi Scott. Thanks for the great content. Would you do a video on Reaction Engine's recent success in testing their pre-cooler?
Thanks, Scott. A very professional and understandable video!
Thank you for this very informative video Scott.
4:30 space shuttle in present tense - shall we tell him ?
When the footage of the dragon capsule escape system test failure came out and people on the news were talking about "clouds of smoke seen for miles" I just remember seeing the footage and saying aloud, "That's not smoke guys; that's nitrogen dioxide." Thanks for the "Ignition" recommendation; I'm so happy it was reprinted.
Thanks. After one of your recent videos, I was left wondering about the term hypergolic.
Don't forget that the British Black Arrow used a quasi-hypergolic mixture of catalyzed hydrogen peroxide and RP-1. Once passed over a catalyst, HTP decomposes into very hot steam (about 800F IIRC) and molecular oxygen, which readily combusts with RP1 and probably other fuels as well. This remains an under-utilized combination. Yes, it is lower performance, but it more than makes up for it by the lack of cryogenic qualities, low toxicity, and high density.
I'm currently writing a large assignment on hypergolic fuels. This has been such a good help, since getting a grasp of the subject is.. well, rocket science.
Never looks away from the camera toward a prompt screen or says "err" whilst searching for the right word. He knows what he is talking about. Respect.
Great explanation, as always! Thanks.
HF is not a very strong acid, it just happens to be able to etch glass and is very toxic. It's just a tad stronger than formic acid but nowhere near nitric acid. As you go down the halogen group the acids get stronger, so HF is actually the weakest of them, followed by HCl then HBr and HI.
Fun fact as a side note: that part of the safety data sheet could very well also be from some of the nastier essential oils. (Though pretty much all of them are nasty when concentrated)
TheYear2525 More fun facts: Hydroiodic acid is listed as a U.S. Federal DEA List I Chemical, owing to its use as a reducing agent related to the production of methamphetamine.
An alternativ to Aerozine 50, used by Ariane 2-4 is UH25, wich is a mix of 75% UDMH with 25% Hydrazine.
Thanks for another really fascinating video!
Nice, a video on monopropellant should be very interesting too :D
Good explanations - thanks!
You are amazing Scott I love space because of you bro
Explosive, Corrosive, Toxic, Carcinogenic and Orange... I did not expected this channel to talk about politic. :D
very nice explanatory video!
While watching OLF I thought.. 🤔 Hmm I wanna brush up on my knowledge about hypergolics.. Aaaaand Scott just released exactly this 👍
Thank you Scott for this very informative video! I would, however, like to point one thing out: Hydrofluoric acid is not particularly strong, it is only about as strong (or, rather, weak) as citric acid. Despite this, it is dangerous to handle since it can penetrate the human skin. Additionally, it is the only acid able to corrode glass.
imagine what would happen if a rocket fueled with hydrogen and flourine blasted of. The shower of hydrofloric acid wouldn't be so good for the launch pad I'm guessing.
Thank you Schart for this human skin! I would, however, like to handle hydroflouric acid. I think it is the only acid that can corrode (haha) glass omg what a moron sorry had to say something
Great job for this information
Great video, Scott!😍 how about a follow up video about pyrophoric substances?🙌🏼
Hey Scott, love your vids. Have you ever considered hanging up some sound panels to improve your sound quality? You can also diy them with old towels and cover it with a nice space or kerbal print ;o) Just a thought.
The knowledge drop is both intense and effortless, must be a Scott Manley video!
Thanks...Scott..!
Things spontaneously combusting seems to be a theme in rocket science.
Rockets, unsurprisingly, have a lot of uses for combustible things.
incredible explanation. thank you
Hi Scott. I like your videos a lot. I was thinking about how different thrusters work, and about how gimbaling on engines works. Just ideas for upcoming videos? Regards. Laust, Denmark
Yup. Used to work with MMH/NTO systems. Fun stories!
You rock Scott keep it up
Scott Manley you are the man
I misunderstood the title as being what are some hypergolic fuels that aren't like the rest, but still a good video.
Scott: Make a video on the advantages to remplace hypergolic control thrusters with cryogenic propellants with ignition for RSC and main propulsion, this allows higher isp, is not a nasty stuff and you can use all the fuel you have in what you most need (propulsion or RSC).
Why few spacecraft took advantage of that? taking into account how easy is to store cryo fuels on space (in case you have clear enough how heat flow work on space, emission coefficients, reflection, etc)
I took a lotta antihistamines and I’m just trying not to fall into my phone but I can oddly comprehend 90% of everything chemistry he’s sayin
Pete is never wrong it’s my email for Netflix they always hung up on Netflix support
Scott... are you a chemist or an astrophysicist?.. or both? this stuff is friggin awsome. thnx dude.
Scott I process E-Waste for precious metals, HNO3 is routinely used by myself to form Aqua regia, also in the separation of Gold from certain base metals. The brownish red gas that is produced in the reaction, is that Nitrogen Dioxide? Great videos! Keep them coming and as always "Fly Safe"!
Yup the gas is nitrogen dioxide. 😁🤓
Fantastic video, I wish you could have mentioned the necessity of sticking with hypergolic fuels for relighting rocket engines without fail. For when you absolutely positively need to get off the surface of the moon. That, and the problems with housing solid rocket motors in orbit.
Science Friday with Scott Manley!
Just learned what a methyl group is. Thanks Scott!
I sensed this video coming when I saw you discussing this on the Twitter
Another fun area where hydrogen peroxide is used, if i remember correctly, are torpedoes. Now those are again often used in subs. So now you have a very reactive substance that releases a ton of hot gas whenever it breaches it's container and it's all contained inside a pressure vessel several hundred meters beneath the surface. Not to mention a lot of these torpedoes used it as an oxidizer so there was lots of fuel for it to react with as well.
I'm still waiting to see a clearer explanation of the N2O4 cloud that enveloped the Starliner a few days ago while still in the air. In addition to looking bad my concern is that it may have played a role in the failure of the third parachute. Additionally, when the capsule landed, quite close to the service module, the fumes blew towards the capsule and if they use venting to equalize the capsule pressure so they can open the door then fumes could easily get into the capsule and that would not be good for the crew. Something just didn't look right with the N2O4 cloud as the chutes were deploying.
Monomethyl hydrazine and Nitrogen Tetroxide... Fun, fun, fun. Working with that stuff on the shuttle program in the early 90's was exciting.
_"Fun, fun, fun."_ Reminds me of the saying that "Some people need the spice of mortal danger to make life palatable." 🙃
2:41 reminded me the "Only the good" episode of Red dwarf, when Rimmer was trying to memorize the name of some compound and then trying to say it.
When you've got to put on a moonsuit that rivals the newest generation of spacesuits just to be around these chemicals, most people generally look for another line of work.
Have to be better than a space suit, that only has to withstand direct sunlight and vacuum for a while. The suits need to survive conditions like that in the Jovian upper atmosphere. Jupiter's colours come from having an atmosphere mostly made from all sorts of nasty nitrogen and hydrogen compounds.
The german DLR made experiments with a mixture of N2O (laughing gas) and ethylene/ethan. The mixture is not hypergolic by itself, but the laughing gas can be decomposed by a catalyst. The decomposition ist exothermic and the gas is hot enough to ingnite the resulting oxygen/fule mixture. Let's call it indirect hypergolic ... Both laughing gas and an ethylene/ethan mixture are only little harmfull to health and environment.