Hydrofluoric acid is no joke. When I was younger, I worked in a wafer fab (a facility for making integrated circuits) and inadvertently got some 100% HF on the sleeve of my jumpsuit. I only noticed it after about 20 minutes when I saw that the material of the suit was flaking off and disintegrating. I didn't feel any pain until another 10 or 15 minutes while I was on the way to the hospital. The doctors had to inject my arm with a silver solution to try to get the HF to bond to that instead of my bones - my arm was ballooned out to about twice its normal, scrawny size due to the HF and the injected treatment. The pain was almost indescribable. They said I probably only got a few milliliters on me. I was VERY careful of HF after that.
I once managed a small lab at a teaching institute. My direct supervisor (totally ignorant of chemistry) allowed another researcher to “do his stuff” in our lab. Ultimately several people were grateful I did the research & was ready for “the accident”......... the researcher using the HF did not know any of emergency procedures, or how to clean up & decontaminate... aah those were the days
P N my high school chemistry teacher powered a tin turbine with steam generated by Hydrogen peroxide reaction with potassium permanganate I one demo he covered Newton’s Third Law, exothermic reactions and catalysts.
Yeah, electronics PhD student here, HF is a bastard. Luckily we now have RIE gas etching (basically fancy microwave which creates plasma from gas, the plasma then etches the wafer), so we don't have to use it in liquid form.
@P N a friend of mine in high school would dig up all the old 1950s and 1960s chemistry texts and make things like NI3. We found that the key problem was obtaining some of the reagents, even the things used to derive them. Seems in the 1950s and 1960s certain chemicals were simply easier to get. Our lab techniques were poor though, and the books didn't give you step-by-step how to do it, but assumed some theoretical and practical background and NI3 was probably the most exciting thing we made.... although a friend of ours did a backyard fireworks show with DIY ignitors etc... he tried carefully to get purple fireworks working, but seems the chemistry for the colour was extremely sensitive to contamination. These are all things high school chemistry should be able to help with, but I'm quite sure the teachers have no clue at all and are only concerned about children graduating with all their fingers.
"fluorine is a better oxidizer than oxygen" this is one of those simple sentences that masks an absolute horror for basically any organic substance that doesnt want its oxygen ripped off.
If fluorine had been more abundant during Earth's formation would life than be based around carbon, fluorine and hydrogen instead of oxygen? Than fourine would be completely safe and we would have more powerfull rockets :D
I heard about theories explaining how silicon could replace carbon in the formation of life, but I doubt you could make the same case for flourine since differences in chemistry of flourine vs. oxygen are much more pronounced than chemistry of carbon and silicon. Different groups in the periodic table for the former pair.
Zero time-lost accidents, even. Given what he was working with, and the potential for mishaps, and those mishaps he *did* have that thankfully avoided leading to people getting seriously hurt, that's damn impressive. And he's not even entirely sure how he managed it.
Favourite bit in the book; Clark weeding out applicants by having a massive bang go off in the middle of the interview; the ones still with clean undies at the end got the job.
"It is also hypergolic with such things as cloth, wood and test engineers." Drat, there goes my revolutionary plan to line a rocket's interior with test engineers.
@@nikkiofthevalley At least nuclear weapons abide by the always never principle. It won't go off accidentally, dimethylmercury probably won't abide by that principle.
The chapter on Monopropelants has my favorite overall quote. "Any intimate mixture of a fuel and an oxidizer is a potential explosive, and a molecule with one reducing (fuel) end and one oxidizing end, separated by a pair of firmly crossed fingers, is an invitation to disaster."
@@williamchamberlain2263 Considering this is the same book which outlines people putting aluminium, mercury, and chlorine triflouride in rockets to get better specific impulse values...
They actually managed to persuade _five_ fluorine atoms to huddle around a single chlorine, to make chlorine pentafluoride, an even more energetic compound.
@@drtidrowChemically speaking, ClF5 still has 2 electrons left to form covalent bonds with yet two more fluorine atoms.. It just takes an even madder scientist
Having ADHD, I would probably never be allowed to work with such chemicals. I would enjoy it too much. "Hey, what happened to my ozone? That Rubix guy better not be playing with cesium again!"
This incident resulted in a single casualty, who suffered a heart attack while running from the scene. Casualty continued running for a further hundred yards or so before collapse.
Derek Lowe's 'Things I Will Not Work With' blog led me to Ignition. Also worth a read. A quote: "The general rule is, if you’re looking for the worst organic derivatives of any metal, you should hop right on down to the methyl compounds. That’s where the most choking vapors, the brightest flames, and the most panicked shouts and heartfelt curses are to be found. Methyl organometallics tend to be small, reactive, volatile, and ready to party."
I LOVE that book! And you didn't even mention the monopropellant madness! "Any intimate mixture of a fuel and an oxidizer is a potential explosive, and a molecule with one reducing (fuel) end and one oxidizing end, separated by a pair of firmly crossed fingers, is an invitation to disaster!" He then goes on about how the first monopropellant engines ran on nitroglycerin, and other monoprops that they had "never been able to fire them in a motor, since they invariably detonated before they could be poured into the propellant tank".
"It is hyperbolic with test engineers." How was THIS fact discovered? Aren't test engineers rather expensive to use as rocket fuel? "Hello, could you make 100 lbs of dimethyl mercury?" "Are you *INSANE*?"
One of my favourite lines from the book comes from the chapter on the experimental high-energy liquid monoprops: "On paper, it sounds ideal... But! Any intimate mixture of a fuel and an oxidiser is a potential explosive. And a molecule with one reducing (fuel) end and one oxidising end, separated by a pair of firmly crossed fingers, is an invitation to disaster". This humorously understated comment (in keeping with the rest of the book) confirms the fact that yes, quite a lot of early experimental propellant research involved the chemical equivalent of crossing one's fingers and hoping for the best!
Our catchphrase at XCOR was, "If you can't spill it on your shoe, we don't want to use it." During a pump test, Dan Delong actually detected a small LOX leak when his foot got cold, so he took his shoe off and let it warm up to allow the oxygen to dissipate- so it's a rule we really did use.
When I worked at Rockwell in eighties we lost a couple of engineers that were cleaning a rocket fuel tank, hydrazine (?) and forgot the safety requirements at KFC. Those kind of mistakes are fatal.
Him: "If liquid Fluorine wasn't reactive enough, how about you try to put even more Fluorine in?" Me: "Oh, no, he's going to talk about Chlorine Trifluoride, isn't he?" Him: "Chlorine Trifluoride!" Me: "I knew it!"
In the old west, Cowboys rode horses and had pistols and rifles. Engineers drove iron&steel trains and had double-barreled shotguns; 12, 10, and sometimes even 8-gauge. Space cowboys use nukes and pusher-plates with giant hydraulic systems. Space engineers use antimatter or other exotic fuel and a drive system that would be about as intelligible to 18th-century science as the vision of the four wheels was to Ezekiel.
@@abhinavgirish1609 Wasn't it one of the Glushko's experiments? There was an even worse one, where pentaborane/hydrazine fuel mixture was doped with beryllium.
Fifteen hundred comments so far. Enjoying reading some of them. For two years, 1965-67, I was a chemist at the Rocket Propulsion Laboratory, Edwards Air Force Base. Worked with much more dangerous chemicals than you mentioned. Shock sensitive explosives, and toxins like beryllium fluoride. One chemist, a Major, became incapacitated and had to retire. Two years were also spent contributing to the Skunkworks, 1963-65. That’s another story.
Derek Lowe, in his series on "things I won't work with", mentioned one compound that was sensitive to air movement (as in breathing on it) and would proceed to explode.
The most entertaining book on chemistry I’ve ever read. The section on hydrogen peroxide is a real eye-opener for anyone who thinks of this compound as merely the incredibly diluted solution sold in stores as a hair bleach or (somewhat incorrectly) as an antiseptic.
Hi I work on the RL10 and back in the 60-70's Pratt an Whitney did extensive testing using the RL10 with hydrazine and fluorine. On the E-7 test stand (deactivated in 1974 torn down in 1995 still had hydrazine trapped in the 1000 gallon tank found out the hard way) We had a whole Fluorine passivation area to treat the hardware. I was to young but saw many test tapes ran very well but when it blew it did so impressively. They also did Hydrogen and fluorine, and hydrazine and oxygen. Take care.
You missed one nasty fuel ... Pentaborane (aka: the "green dragon")! A complex mixture of boron and hydrogen atoms with a nasty garlic smell, burnt with a brilliant green flame, and had acute toxicity that rivaled some nerve agents. And it was produced in massive quantities to be used as "zip fuels". The remaining unused kegs of the chemical were either burned off or dissociated with hot water / steam yielding hydrogen and far less toxic boric acid solution (the "dragon slayer" process). You briefly touched the subject of zip fuels in the XB 70 video in mid 2018.
Hydrogen-fluorine combo: "... there is a niche for upper stages - where the rocket is far enough down-range that the exhaust" ... would be falling on _someone else._
Just another example of what is ok in small amounts but deadly in large quantities. Even oxygen is toxic if you get too much. (2bar of pure O2 will kill you.) And nitrogen will get you drunk at high enough pressure, (nitrogen narcosis). Drink too much water and you die. How much is often far more important, than what.
@@kamuroshow4884 Presumably because during their tests with it, an accident meant they were in the unenviable position of being able to inhale the stuff.
Which came in handy when the first industrial-sized batch of ClF3 was being tanked, and the tank supports started giving way. Luckily, the only casualty in the accident was a non-fatal heart attack suffered by one of the crew as they set new records in the To the Horizon Dash. (When I was teaching computer techs who were going to have to work in a high energy chemistry lab (Somebody has to pull network cables, fix the systems, and make sure the PhD in the lab isn't trying to log in with the shift lock key toggled) the Last Rule was "If you see me running, try to keep up."
Ignition is a superb book, although I've only read the PDF version--didn't realise they'd reprinted it! Just ordered my copy now (Amazon UK aren't out of stock...).
"...it is also hypergolic with things such cloth, wood and test engineers" You should defintiv do more voiceacting (like audiobooks), we will listen to you and enjoy for hours (or even days).
I worked in the semiconductor industry as a technician. We used hydrofluoric acid in several processes. It is seriously nasty stuff, we used to have first aid drills SPECIFICALLY for hydrofluoric acid. We were told a palm print sized exposure was fatal. Every first aid kit in the whole 40 football pitch sized factory had calcium cream for hydrofluoric acid exposure.
For discussion of more chemicals whose structures make you want to scratch out your eyes in horror, I would like to recommend a blog called "In The Pipeline," by Derek Lowe. Specifically, look for a series of entries under the category "Things I Won't Work With."
Found the blog years ago through XKCD, and then followed from there to the book. To the best of my recollection, that blog and that book are the only things that have literally had me rolling on the floor laughing.
You want to see Lowe's blog post on "Satan's kimchi", i.e., FOOF (here: blogs.sciencemag.org/pipeline/archives/2010/02/23/things_i_wont_work_with_dioxygen_difluoride). Now 𝘵𝘩𝘦𝘳𝘦'𝘴 an oxidiser.
He has an amusing post on Hexanitrohexaazaisowurtzitane and the synthesis of other compounds with far more nitrogen in them than any sane man would wish for. (If I recall, it becomes MORE stable when mixed 1:1 with Trinitrotoluene.)
Hah, I got hold of a digital copy some years ago. Excellent book. My favourite bit is probably the reaction test where two tiny droplets were placed on a watch glass and allowed to touch, and the reaction reduced the watch glass to powder. Talk about high explosive...
One of my favourite bits is when Clark happened to notice a particular lab sample (some exotic nitrate or other) turning brown rather rapidly, with just enough time to yell "everybody get down!" before the beaker exploded and shot across the top of table they were all sitting around.
For a *really* nasty propellant, look up "Nuclear salt-water rocket" on Wikipedia... When I read this, my first thought was: "Could Dr. Strangelove please refrain from inventing stuff when he's *that* drunk...?"
Just checked them out per your recommendation. Absolutely amazing stuff if we can figure it all the way out. The theoretical aspects are fascinating and the numbers produced are staggering.
ANY test need to be conducted no closer to the Earth that on the Moon. The location need to be chosen so that the exhaust is directed well away from the Earth and ANY satellite or active space station.
I wonder if the book mentions the various types of nuclear rockets. Nuclear pulse propulsion, where you use nuclear bombs behind a pusher plate, would actually be fairly safe "fuels" to handle in the sense that the bomb devices would be hard to accidentally detonate. Nuclear thermal rockets like NERVA are a different story; once the reactor has gone critical the fuel becomes pretty lethal stuff to be around. My favorite has to be the nuclear salt water rocket, which uses an open cycle liquid fuel core. The liquid is basically water with uranium or plutonium salts dissolved in it, which are injected into a reaction chamber and mixed to become supercritical, heating the water to steam and blowing it out the nozzle as reaction mass, along with all the fission products. High Isp and high thrust, it's almost a torch drive but using it in atmosphere would be unconscionable, since it's basically a giant flying Chernobyl disaster.
I guess robots could use for aerospace vehicles and rockets, like, when AI will rebel against humans. They can cut expenses on concentration camps that way.
As far as I remember nuclear salt water rocket engines are more like taking the most powerfull milisecond of Chernobyl, multply that my 64 if I remember correctly, and then just have that running for a few minutes instead of a milisecond.
Reprinted ? My word, I have ordered it immediately! Ignition! is the best chemistry book I've read during my lifetime (on par with Gergel's "Excuse me sir, would you like to buy a kilo of isopropyl bromide ?")
My thermo/gas dynamics and propulsion professor in the early '90s at Ohio State was Rudolph Edse, an honest-to-God German rocket scientist. While doing some background research in grad school, I found some reports he wrote in the '50s and '60s describing hilariously dangerous rocket fuel experiments that his research group at OSU did. IIRC, they did a couple tests of a hydrogen/fluorine fueled rocket engine in an empty lot across the river from campus before somebody asked them if they could please stop killing the grass...
Yes indeed Scott, I checked this book out of the local library circa 1960's, now have two copies including a copy recently given to me as a gift from my best friend. Quotes like "hypergolic with sand,water and test engineers",You summed up the book well, Thank you - Ken
And then he gets around to talking about fluorine combined with chlorine... A chemical so aggressive that the German chemical weapons program discontinued their study in it because they realized that it could never be transported. Should a passing airstrike happen any containment vessel with chlorine trifluoride would simply delete anything that the bomber had missed.
1972 ! My gosh Scott you are a young lad. Born about the time I was getting out of submarines. Ethanol. - in my submarine days that was known as “torpedo juice” used as a propellant and commonly used by the crew for libations; if they could get away with it and if you were willing to suffer the wrath of the captain. I immensely enjoy your RU-vid postings. Keep it up😊
I always remember the dimethylmercury bit, its a potent reminder that what someone is asking for and what they want are two different potentially life saving things
In my old textbook, the example for that lesson was someone accidentally buying oxalic acid for a rhubarb dish, instead of the substance marketed as "anti-oxalic acid" back in the day.
I've wanted a copy of that book since I read "Excuse me, sir ..." I'm surprised you omitted the ClF3 spill story, that is one of my favorite anecdotes.
Simon Ingram I would say "walk a mile in another man's shoes" but it was really an embarrassing combination of shaking, running, and tip-toeing my way out of there.
Let's add the famous quote from Isaac Asimov's foreword (I've seen a part of it on doors at the ESTEC ESA center in Holland): "Now, it is clear that anyone working with rocket fuels is outstandingly mad. I don't mean garden-variety crazy or 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."
Ordered the book in Feb direct from the publisher. Still waiting. :(. It has shipped though. Just turns out the remarkably low shipping price to the other side of the planet may have involved actual ships.
If you're talking about Apollo 1 (and you must be, there wasn't any other such disaster), they were going to fly on Stautn I, not Saturn V (and no, not Saturn IB either). still, there were two unmanned test flights of Saturn V before Apollo 8, and of course last ever flight of Saturn V launched Skylab, but this one used shroud with the same diameter as the 3d stage (which Was the Skylab, converted from SIVB third stage, and not actually a rocket stage BTW)
also, Apollo 1 did have an escape tower, which was a problem during the disaster because they were worried that it might get set off by the heat and flames and make an even bigger disaster.
My (relatively) near-experience with such substances occurred in college, when--for my elective "X experiment" in chemistry--I expressed interest in liberating fluorine. "No, you don't want to liberate fluorine," said my professor. Some years earlier, he related, another student of his had done that, and the experiment was successful--WAY too successful. "Seeing laboratory glassware burning with green flames," he said, "is not something I care to experience again!" When I suggested synthesizing dinitrogen tetroxide as an alternative "X experiment," he smiled at me and muttered something about a death wish (perhaps fortunately, I was unaware of Hydyne at that time)... :-)
How about crush mercury temprometers as teenager on the floor and not able to clean in it up from the synthetic carpet that cover the whole bedroom -I lived there 10 years .I guess this why im wierd ,( i slighty remember this happened twice ) ; Next malfuntion as teenager -My father ( dead by now) found a a discharged pot of selfglowing yellow green power on a local city dump,, physorus ? used to make signs glow i belive -some of it ended up on same carpet - a lot ...
6:00 "Putting more fluorine into the system" isn't the full story. Teflon, PFTE, has lots of fluorine, but makes for a horribly bad rocket fuel (even though it would allow the rocket to slide to the launch pad really easily...). No, what does matter is the reactivity of the fluorine. Fluorine itself tries very VERY hard to get an additional electron. And it is reactive exactly when it doesn't have one. Like in F2, where both fluorine atoms hold on to their electrons with the same strength, and in ClF3, where the central chlorine can hold on to its electrons pretty well too, making the Cl-F bonds tentative at best. On the other hand, if you have fluorine in a compound in which it has sated its hunger for an eighth electron, like in HF or in PTFE, it's fairly docile stuff actually, because you have to invest huge amounts of energy to get it away from that extra electron it has managed to grab...
Yes, THX much for that clarification. My grandfather illustrated reactivity by explaining salt. Chlorine gas is corrosive, toxic, and acidic, and Sodium reacts violently with oxygen. But Sodium Chloride is one of the most ubiquitous and useful substances on the planet (below water, oxygen, chlorophyll, hemoglobin, and DNA).
Actually, PTFE makes a pretty decent oxidizer. It's used in a thermite-like composition with magnesium to make flares and pyrotechnic igniters for solid rockets. www.vti.mod.gov.rs/ntp/rad2009/1-09/bosk/bosk.pdf
Great book Scott, agree with you 100%. Had mine for about 30 years. Attempted to make RFNA - cough cough - and almost lost a lung. Another good author from the same generation as Clarke is Willy Ley - Rockets, Missiles and Space Travel. Less technical and more historical but also a good read.
I read some of an aerojet book, they tested nitromethane. They said that when the engines ran out of fuel they exploded violently. That is exactly what nitro dragsters do, slight change in combustion and HUGE fireball.
Seconded! The CD video was very well presented, but I'd also like to hear Scott's opinion on the technology from a real-world, not Kerbal, perspective (although he's undoubtedly chatted about them before during livestreams etc.)
Great review of a very interesting book. I've always had a fascination with the darker side of chemistry (from my love of true crime) and I've heard of the lethality of some of these compounds before. I didn't realise there is such crossover in uses haha!!!
There's a web comic that's been going for about 20 years now called freefall, it's about a genetically modified wolf working as a awrospace engineer in a teraformed planet. One of the characters as punishment is forced to work at a fast food restaurant and when asked what would happen if he quit is told he'd be forced to work at a chemical plant that produces clorine triflorideand then is told of it's hypergolic properties.
It's described as a "cleaning compound" (which is true) and after being told how dangerous it is, the character asks, frightened, "what if that stuff gets on *me*?" Two answers, given by two different characters in rapid succession: "You will be very clean." "And on fire."
The comic is freefall. When it mentioned chlorine triflouride I assumed it was a joke as chemically it doesn't make sense. A web search and I realised that it does exist but having it around doesn't make sense.
Another problem with liquid ozone / oxygen mixture is the tendency for ozone to separate out due to its higher density. One then obtains nearly pure liquid ozone at the bottom yielding a large KABOOM.
My grandfather use to work with liquid rocket motors. He told me a story of a man who sprayed a hose in what he believed to be an empty 55 gal drum. Previous fuel evaporated out and left sensitive crystals. As soon as the water hit, "he turned into a red mist." Another time of an evacuation siren, ran outside behind a tree. "All clear" siren sounded and 30 seconds later, the roof blew off the building. I'm here today because he waited. "Unsymmetrical dimethylhydrazine" was the one he talked about most.
Missed out on Hydrogen Peroxide. The Messerschmitt Me 163 Komet fighter fueled by it sometimes exploded on takeoff, sometimes exploded on landing, and sometimes just exploded.
John Francis Doe An important question here is, was he arrested before or after the explosive risk to innocent life detonated in inevitable fashion? Hopefully "before"?
@@scottmanley I liked the part on using boron in rocket fuels. On paper it seems ideal because it's heavy. In practice boron compounds proved to be impossible to make work because they left tarry deposits everywhere inside the test engines. The worst part was how the deposits would build up in the nozzle throat, despite the high velocity hot gas flowing through, building up until choking the combustion chamber down to the point where the pressure would make it explode if the fuel supply wasn't cut off. Has me wondering if there are any newer alloys or surface treatments that would be non-stick to boron compound combustion byproducts - in the hot inside of a rocket engine. Or might there be newer chemistry knowledge that could keep a boron compound fuel from producing those sticky byproducts?
Scott - My father and I both worked at Aerojet-General - My father was a propulsion scientist and chemical engineer. He was tasked with working in the 1970s with a solid fuel component in liquid form, so dangerous that only two people were crazy enough to work the contract - My father and his right-hand man. They had about 10 or so gallons of these stuff in the distillation apparatus and were returning in the company truck to check on it when the entire building went up while they were about 300 yards from the building. They turned the truck around and escaped with their lives. The entire building was vaporized... The blast was so powerful, it sheared the steel columns of the building at the concrete pad and it looked like a giant had punched a hole into the ground where the entire reaction had gone critical. We both saw a lot of accidents and near misses in our time there, each working just over 31 years a piece at the company. ;>)
I managed to get my hands on a PDF of it a number of years ago. After I read it -- repeatedly -- I sent off a copy to a friend of mine who was equally geeky when it came to such things. I've heard that he printed it out and locked himself in the bathroom for the better part of six hours before he finally emerged. A classic. I'm going to have to dodder over to Amazon and see if I can't get a paper copy.
But something more potent than alcohol was needed for the X-15 rocket-driven supersonic research plane. Hydrazine was the first choice, but it sometimes exploded when used for regenerative cool- ing, and in 1949, when the program was conceived, there wasn't enough of it around, anyway. Bob Truax of the Navy, along with 104 Winternitz of Reaction Motors, which was to develop the 50,000 pounds thrust motor, settled on ammonia as a reasonably satisfactory second best. The oxygen-ammonia combination had been fired by JPL, but RMI really worked it out in the early 50's. The great stability of the ammonia molecule made it a tough customer to burn and from the beginning they were plagued with rough running and combus- tion instability. All sorts of additives to the fuel were tried in the hope of alleviating the condition, among them methylamine and acetylene. Twenty-two percent of the latter gave smooth combustion, but was dangerously unstable, and the mixture wasn't used long. The com- bustion problems were eventually cured by improving the injector design, but it was a long and noisy process. At night, I could hear the motor being fired, ten miles away over two ranges of hills, and could tell how far the injector design had progressed, just by the way the thing sounded. Even when the motor, finally, was running the way it should, and the first of the series was ready to be shipped to the West Coast to be test-flown by Scott Crossfield, everybody had his fingers crossed. Lou Rapp, of RMI, flying across the continent, found him- self with a knowledgeable seat mate, obviously in the aerospace busi- ness, who asked him his opinion of the motor. Lou blew up, and de- clared, with gestures, that it was a mechanical monster, an accident looking for a place to happen, and that he, personally, considered that flying with it was merely a somewhat expensive method of sui- cide. Then, remembering something he turned to his companion and asked. "By the way, I didn't get your name. What is it?" The reply was simple. "Oh, I'm Scott Crossfield."
My late grandpa, Vic Horton, worked for Thiokol's Reaction Motors Division prior to his long NASA career. One of the projects he worked on was the XLR-99 engine for the X-15 and was present during its first successful test firings and throttling demonstrations. Later, after he joined NASA in 1958, he became involved in the actual X-15 flight tests.
I totally forgot about this book. I actually have a copy and started to read it a few years ago, but I never finished it. Time to change that. Thanks for reminding me.
Safety Time Machine Key Points 1. Automatic door lock. 2. Goes invisible. 3. Moves objects out of the way. 4. Can stand extreme weather. 5. Has solar panels. 6. Has camera/TV inside so the time travellers can only observe history. 7. Has rocket fuel. 8. Rocket fuel fades extremely fast in the sky. 9. Automatic probability control so history doesn't change on it's own. 10. Uses wormholes to time travel.
what effect did the mercury have on performance, I'd imagine it would cool the exhaust but probably increase mass flow rate, but lower the specific impulse by lowering the kinetic energy of the exhaust products.
I believe the intention was the opposite; to increase thrust/specific impulse by densifying the propellant and therefore INCREASING the velocity of the exhaust gas (while also doing useful things like keeping chamber temps under control, as you mentioned). But it's been a while since I last read the book, so I might have that arse-backwards... don't quote me. ;) EDIT: Yep, I had it backwards, you were correct. Specific Impulse dropped sharply, but Density Impulse (Isp x Propellant Density) increased significantly to the point where there might have been major performance benefits in applications with a low "tank loading factor" (e.g. air-to-air missiles, which have a fairly low ratio of dry mass:tank volume), if only the stuff wasn't so damn toxic. In any case, it wouldn't have had any major benefits for an orbital launcher with a high mass:volume ratio, where Isp is king.
