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Space Forum / Shuttle / June 2007resid. hypergolics
I was watching a repeat of the post landing briefing and Mike Linebaugh was talking about purging residual hypergolics from the orbiter after landing... are those LH2 and LO2 and I assume its whats left over from liftoff in parts of the pumps, pipes? whatever... wouldnt they just evaporate or sublime or whatever they do out in space? or if they are in a closed system they might still be present? Or is he talking about whats left over in the re-entry engines. >I was watching a repeat of the post landing briefing and Mike Linebaugh was >talking about purging residual hypergolics from the orbiter after [quoted text clipped - 3 lines] >closed system they might still be present? Or is he talking about whats >left over in the re-entry engines. It is what is left over in the "re-entry" engines -- called the Orbital Maneuvering System. The small jets that control attitude -- called the Reaction Control System -- are also hypergolic. Danny Deger > I was watching a repeat of the post landing briefing and Mike Linebaugh was > talking about purging residual hypergolics from the orbiter after landing... [quoted text clipped - 3 lines] > still be present? Or is he talking about whats left over in the re-entry > engines. LH2 and LO2 are not considered hypergolics. And they're not terribly dangerous, at least compared to hypergolics. You can breathe some of their vapors with no ill effects (in fact, you NEED to breathe some O2). The shuttle uses MMH and nitrogen tetroxide as hypergolic propellants for the RCS and OMS engines. Those are what have to be purged, as they're extremely hazardous to come in contact with, even in low concentrations. http://en.wikipedia.org/wiki/Hypergolic >> I was watching a repeat of the post landing briefing and Mike Linebaugh >> was talking about purging residual hypergolics from the orbiter after [quoted text clipped - 15 lines] > > http://en.wikipedia.org/wiki/Hypergolic Add to that hydrazine for the APUs and there are some nasty chemicals on board...  Signature--- there should be a "sig" here snip > Add to that hydrazine for the APUs and there are some nasty chemicals on > board... Good point. The APU fuel is pretty nasty stuff. Danny Deger NASA offered me $15,000 to take down my web site. Take a look and see why. www.dannydeger.net >> I was watching a repeat of the post landing briefing and Mike Linebaugh >> was [quoted text clipped - 11 lines] > LH2 and LO2 are not considered hypergolics. And they're not > terribly dangerous, at least compared to hypergolics. I was reading that there is a "spark plug" in the main combustion chamber that ignites the gasses... then what are those sparks that shoot outside the SSME just before liftoff? >> LH2 and LO2 are not considered hypergolics. And they're not >> terribly dangerous, at least compared to hypergolics. > > I was reading that there is a "spark plug" > in the main combustion chamber that ignites the gasses... then > what are those sparks that shoot outside the SSME just before liftoff? Correct. The "sparklers" you see are there to burn off residual hydrogen that may leak out before launch or during a launch abort so there's no chance of a fire or explosion. SignatureGreg Moore SQL Server DBA Consulting Remote and Onsite available! Email: sql (at) greenms.com http://www.greenms.com/sqlserver.html >>> LH2 and LO2 are not considered hypergolics. And they're not >>> terribly dangerous, at least compared to hypergolics. [quoted text clipped - 8 lines] > leak out before launch or during a launch abort so there's no chance of a > fire or explosion. Did anyone see the Delta Heavy launch? It had/has lots of unburned hydrogen around the booster that ignites at lift off. It looks like the darn thing is going to blow up. SignatureDanny Deger NASA offered me $15,000 to take down my web site. Take a look and see why. www.dannydeger.net > Did anyone see the Delta Heavy launch? It had/has lots of unburned > hydrogen around the booster that ignites at lift off. It looks like > the darn thing is going to blow up. That seems to be part of the RS-68s design, using lots of hydrogen to chill down the engines just prior to ignition. It was anticipated and allowed for with insulating blankets and inert gas purges, but it sure looks like a Bad Moment In Launch History until it lifts off. I've heard a hint that Boeing/Rocketdyne is working on the problem. --Damon >> Did anyone see the Delta Heavy launch? It had/has lots of unburned >> hydrogen around the booster that ignites at lift off. It looks like [quoted text clipped - 7 lines] > > --Damon I have recently "retired" (see my web site) from NASA and the word on the street at NASA was the first thing Boeing would have to do to man rate the Delta Heavy is to have it NOT look like it is going the blow up at lift off. SignatureDanny Deger NASA offered me $15,000 to take down my web site. Take a look and see why. www.dannydeger.net > I have recently "retired" (see my web site) from NASA and the word on the > street at NASA was the first thing Boeing would have to do to man rate the > Delta Heavy is to have it NOT look like it is going the blow up at lift > off. Everyone knows that management is concerned first with appearances. It's true in *every* organization, not just NASA. It prevents a lot of confrontations with upper management, who usually don't have a clue about the *real* day to day processes in the organizations they manage, if you get rid of *anything* that may look out of place to them, even if you know what you're "fixing" isn't *really* a problem. It's similar to what you have to go through to get ISO certified. ;-) In the case of the Delta IV Heavy, the fireball at liftoff isn't supposed to be a problem, but it does have the effect of getting your customer's management worked up, so it will almost certainly be fixed. Even if NASA never flies anyone on a Delta IV Heavy, Boeing's other customers will almost certainly be happier if they don't see a fireball on the pad every time they launch a payload with Delta. Jeff Signature"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety" - B. Franklin, Bartlett's Familiar Quotations (1919) >In the case of the Delta IV Heavy, the fireball at liftoff isn't supposed to >be a problem, but it does have the effect of getting your customer's >management worked up, so it will almost certainly be fixed. Even if NASA >never flies anyone on a Delta IV Heavy, Boeing's other customers will almost >certainly be happier if they don't see a fireball on the pad every time they >launch a payload with Delta. Maybe I've been an engineer too long, but this makes no sense to me. If I'm a customer, I want a safe ride to space, not good cosmetics. I want every Boeing engineer working on fixing something that might fail (like the list of almost-problems on the SpaceX flight, surely Boeing has a similar list), and not something they can show is OK. Worst of all, the fix (to a non-problem) might cause some different failure, so I would not want to be on the first non-fireball flight. Lou Scheffer >>In the case of the Delta IV Heavy, the fireball at liftoff isn't supposed >>to [quoted text clipped - 13 lines] > Worst of all, the fix (to a non-problem) might cause some different > failure, so I would not want to be on the first non-fireball flight. You've never had upper management disagree with engineers because to them something *looks* bad, even though the engineers know it's o.k.? Let's consider the CEV's escape tower. I'd think that even if the engineers could make a solid case for deleting the escape tower, management would absolutely insist on its continued inclusion. Why? Because of the Challenger accident. Yes I know it's a completely different design, but it would be awfully hard to convince non-engineers (e.g. politicians in Washington D.C.) that the CEV doesn't need an escape tower based on this "obvious" evidence. Jeff Signature"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety" - B. Franklin, Bartlett's Familiar Quotations (1919) > ... Boeing's other customers will almost > certainly be happier if they don't see a fireball on the pad every time they > launch a payload with Delta. So far as I know, Boeing has no other customers for the Delta IV except U.S. government agencies. > Jeff SignatureFear is the path to the dark side... Fear leads to anger... Anger leads to hate... Hate leads to banjos... Banjos lead to suffering! |
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