There can be few objects whose alleged imminent death has been cheered by so many so vocally bar perhaps Saddam Hussein's statue in 2003 or one of those boats they floated in the Coliseum where they apparently recreated ancient sea battles 20 centuries ago in imperial Rome. But the criticism of NASA's Ares I crew launch vehicle must be on a par
With US Air Force memos making claims about exploding Ares I first stages (126 Shuttle missions and not one SRB has exploded so why do they worry so?) and newspaper articles about launch abort systems taking longer to design - what the article doesn't mention is that you can't close a LAS design until you know what mass (hello, Orion project office?) it is definitley lifting - the staff of NASA's Ares projects office might be feeling like the Christians that the Romans so happily fed to Lions, again in the Coliseum
It has to be said that the English language pro-spaceflight community's blogosphere (which is overwhelmingly American) is broadly in agreement (see here, here, here and here as examples) over what future Ares I should have, i.e,. none. Sorry NASA but your blog postings don't quite balance things out...
But not to worry as Hyperbola is setting itself on a trajectory to put forward counter arguments (hopefully better ones than NASA has put forward to date) to the blogosphere barrage and give reasons as to why Ares I will survive the US human spaceflight plans review
on June 12, 2009 12:25 AM | Reply
A segmented Titan IV solid motor with the same heritage as the Shuttle SRB did explode at Vandenberg in 1986. And the Challenger motor could have failed the pressure vessel in a similar manner; it was lucky it didn't, been thought the results would have been the same.
The Orion LAS must either be capable of pulling the capsule free of an intact SRB that would now be thrusting at higher G once the Orion comes off the top, or the LAS has to outrun an exploding solid that has been terminated by the destruct system. We can't have it both ways.
on June 12, 2009 7:03 AM | Reply
Toast!
on June 12, 2009 10:37 AM | Reply
But the Shuttle SRB has never exploded in flight. Fact. On your other two points:
1. Orion departure from intact SRB which is faiing some how, this I imagine would either be that, i, there is a control problem with thrust vector control so the Ares I is veering off its correct trajectory or, ii, it is not generating enough thrust
1i upon pyrotechnic separation the LAS will pull Orion in a different direction to the thrusting SRB that is veering away and will not be chasing the capsule that is now on a separate vector
1ii an SRB that is not generating enough thrust is no different in principle to an engine out scenario for a cryogenic engine and so either the LAS can be fired or upper stage separation carried out as normal - depends on where it is in the ascent
2 the termination of the SRB can be carried out 'x' milliseconds after the Orion has departed and by which time it will be at a substantial distance. You don't know what that distance would be and I would suggest it would be sufficient to avoid debris
on June 12, 2009 6:13 PM | Reply
Re your point 1i: you must take into account the so-called "diabolical trajectory" which is range-safety-speak for a situation in which the out of control SRB decides it will fly into the capsule no matter that the capsule is on a slightly different trajectory. I recently spent a fair amount of money being forced by safety people to do analyses that had a probability of ten to the minus tenth over exactly this point. Ares 1 will, as well.
Of course in the end, you can escape from Ares 1 by using more and more LAS thrust, but the loads so generated are tough on crew and structure. You pay for that every time you launch. And it is unnecessary if one were to use a Delta IV or Atlas 5, both without solids.
on June 13, 2009 9:10 AM | Reply
No doubt tenth to the minus tenth is a cheeky phrase of your own but it does indicate that your work suggested that the diabolical trajectory is a very unlikely event. You could just as easily argue that an SRB malfunction on Shuttle ascent could lead to a diabolical trajectory for SRBs jettisoned by Shuttle during a TAL situation. In any ascent you can imagine a wide variety of off-nominal, contingency scenarios but there comes a point where the likelihood of one of them happening and the cost of resolving them means they are scenarios that just have to be left as just possibilities.
on June 13, 2009 5:33 PM | Reply
Rob, I wish ten to the minus tenth was a cheeky phrase, but is the straight truth. We were required to 'be safe" to that level. I don't make this stuff up...it cost real money and time to deal with the requirement imposed upon us.
The way the range deals with an SRB jettison during TAL is the SRB's burn out long before the Shuttle can TAL. So the problem doesn't come up. If it was a problem, the SRBs would be destroyed, and then we are back to the fragment issue.
on June 13, 2009 5:48 PM | Reply
Sounds like an extreme probabilistic assessment. I can only assume that the USAF is being sold a reduced EELV costs argument and has come to think it can use range requirements to nail Ares I's coffin shut and get EELVs selected for Orion. We'll see.