Choice of fuel in a launch vehicle

[propforce]

Which one? The case of behind a wall?<br /><br />I remember during the early days of NASP engine testing, we could not get the hydrogen to mix well in the scramjet combustor, so we kept pumping in more hydrogen until it has more hydrogen than all the air could burn. Well... they didn't burn <i>inside</i> of combustor. <img src="/images/icons/laugh.gif" /> We had an exhaust vent like a chimney just free venting to outside air. The gaseous hydrogen decided it was a good place to go boom inside the chimney <img src="/images/icons/shocked.gif" /><br /><br />The test faciility was next to an airport which they did not appreciate the loud bangs and smokes coming out of our chimney, it tends to disturb pilots during takeoffs and landings, so they sent a few fire engine trucks over. The boss had to go out and assure them that it will not happen again. The next day management directive came down "No injecting hydrogen above the stoichiometric fuel/ air ratio !!!" <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

 

[drwayne]

I had my own - discussions with the fire department when I was in graduate school - fortunately, that was only over *little* things like liquid nitrogen bombs.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[lampblack]

<font color="yellow">I had my own - discussions with the fire department when I was in graduate school - fortunately, that was only over *little* things like liquid nitrogen bombs.</font><br /><br />Wow, Wayne... if the Soviets had ever taken over the U.S., you would have been at the heart of the insurgence with a background like that. <img src="/images/icons/wink.gif" /><br /> <div class="Discussion_UserSignature"> <font color="#0000ff"><strong>Just tell the truth and let the chips fall...</strong></font> </div>

 

[drwayne]

Well, those bombs were kind of like my brain - they sound a lot better than their actual effect.<br /><br /><img src="/images/icons/wink.gif" /><br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>"No injecting hydrogen above the stoichiometric fuel/ air ratio !!!"<p><hr /></p></p></blockquote><br /><br />You know you've got an interesting job when the boss tells you something like that. <img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[drwayne]

For sure.<br /><br />Beats the department chairman telling me "Wayne - no more bombs, OK? no more bombs"<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[trailrider]

I never heard of LO2/LH2 as being referred to as hypergolic. While they may create an explosion or ignition under the right conditions, in most rocket engines I've heard of, they require an ignition source initially. Once burning in the pre-burner or main combustion chamber, they WILL sustain combustion.<br /><br />Hypergolics are generally chemicals which will ignite on contact. Combinations that have been used include fuming nitric acid (red or white, depending on the N02 content)/aniline or furfuryl alcohol or hydrazine (all long obsolete...the last rockets to use RFNA/aniline were the Nike Ajax, and also my own XLR-4C static test article, I designed in high school); N204, which is RFNA with all the H20 removed, and contained under its own vapor pressure/ hyrdrazine or Aerozine 50, which is a 50/50 mix of Unsymmetrical DiMethyl Hydrazine and plain Hydrazine; and some other nasty combinations of chemicals that are too much of a problem to handle.<br /><br />The Titan II used the N2O4/Aerozine 50 mix in both stages, as did the Titans 34-D, Commercial Titan Launch Vehicle and the Titan IV in the liquid stages. Except for Titan II, the others had SRM's as the "Zero Stage", with the Stage 1 being ignited at altitude, rather than "all up" with the solids.<br /><br />As military weapons, the storable hypergols provided rapid launch capability, but long term storage could prove a nightmare! Over time (perhaps a number of years, but not indefinitely), the N2O4 tended to corrode the tankage. One fatal accident occurred in a Titan II sight when a BMAT (Ballistic Missile Analyst Technician) dropped a wrench that bounced off the silo wall and dinged the N2O4 tank. The subsequent leak could have been controlled, except that they flooded the launcher with water, and that created an explosion that killed a member of the cleanup crew. I think that was at Little Rock AFB.<br /><br />The Russians also had big problems with the N2O4/Hydrazine combo in some of their submarines. Leaks

 

[drwayne]

"Not sure whether that will require igniters or not!"<br /><br />I am not familar with any hydrocarbon / liquid oxygen system that is hypergolic. As I mumbled earlier (before I utterly confused things with my mis-adventures), FLOX is hypergolic with many things, including some hydrocarbons.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[drwayne]

By the way, did anybody look at that paper I linked? - there are some interesting concepts - gels and the like in there....<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[propforce]

Yes I did a quick look last night. Not sure I agree with their conclusion though, but did not have the time to go thru in detail.<br /><br />Just for the record, I think it's important to point out that LO2/LH2 combustion is not "hypergolic", the fact that they may "auto-ignite" at high temperature do not make them "hypergolic" and definitely not at liquid phase. Even GO2/ GH2 in a rocket chamber requires an ignition source.<br /> <br /> <div class="Discussion_UserSignature"> </div>

 

[drwayne]

I stand corrected - make that - sit corrected.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[propforce]

BTW, liquid oxygen (LO2) is way more dangerous than liquid hydrogen (LH2) which is contrary to what most believe.<br /><br />I was doing some testing at Sycamore Canyon where we vent out a mixture of gaseous and liquid hydrogen. The LH2 droplets would come down like little sprinkles. I decided to experience this on a personal level, so I walked into the LH2 "rain" with my bare arms exposed. (Kids, do not try this at home) <img src="/images/icons/laugh.gif" /><br /><br />The little cryogenic droplets of LH2 felt like needle pain on my skin as it absorped my body heat and quickly vaporized. But overall, I suffered no physical injuries.<br /><br />I would not do that if it was LO2 !! <img src="/images/icons/shocked.gif" /> The LO2 would explode upon contact with any oily surfaces (which is fuel). A LO2 spill is way more dangerous than a LH2 spill. LH2 will qenerally vaporize very quick whereas LO2 represent an explosion hazard. Sometime we may need to call in a helicopter to lift anyone who's trapped in a LO2 spill area out.<br /> <div class="Discussion_UserSignature"> </div>

 

[drwayne]

I lost a lot of sleep in graduate school to - liquid helium.<br /><br />We would get a big dewar of it in to do low temperature ESR work. It was an open loop system - so we had only a limited time cold - so you had to work through the availability.<br /><br />I was glad when we got the closed loop refrigeration system - and could keep a sample cold for weeks.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[pmn1]

There is an article by Stephen S Pietrobon (Small World Communications) in the May/June 1999 Journal of the British Interplanetary Society about replacing the SRB’s with LRB’s<br /><br /><font color="yellow">The use of high-density hydrogen peroxide/kerosene liquid rocket boosters for the Space Shuttle is investigated as a replacement for the existing SRB’s. It is shown that H2O2/Kerosine outperforms solids, LOX/Kerosene and LOX/LH2 as a general booster propellant due to its high density and moderate exhaust speed. With the same propellant mass and size as that of the current SRB’s, computer simulations indicate payload mass can be increased by a third from 24,950kg to 33,140kg for a 28.45°, 203.7km circular orbit.</font><br /><br /> <br />Hi,<br /><br />ChrisMc on Nasaspaceflight.com has found a PDF of the whole article.<br /><br />Just googled, and found the article you mention is availabe as a pdf: http://www.sworld.com.au/steven/pub/lrb.pdf<br /><br />His site may also have some more things of interest: http://www.sworld.com.au/steven/ <div class="Discussion_UserSignature"> </div>