Wayne Hale on "Black Zones"

[tblaxland]

Some more words of wisdom from Wayne Hale:
http://www.spaceref.com/news/viewsr.html?pid=29847
(you can view the actual blog here but SpaceRef have kindly compiled the relevant series in a continuous article).

I thoroughly recommend reading the whole article but here are some extracts to whet your appetite:

[FONT=Verdana,Geneva,Arial,Helvetica,sans-serif][SIZE=-1]'black zone'... a portion of a manned rocket launch trajectory where the premature shutdown of any or all running booster engines will lead to loss of the re-entry vehicle and crew...[/SIZE][/FONT]

[FONT=Verdana,Geneva,Arial,Helvetica,sans-serif][SIZE=-1]Satellite launchers seek the most efficient way to get to orbit... So most expendible satellite launch vehicles go high early and then pitch over toward the horizontal for the largest part of the rocket burn... [/SIZE][/FONT][FONT=Verdana,Geneva,Arial,Helvetica,sans-serif][SIZE=-1]abort modes and crew rescue are not a consideration. There has been some speculation that if an EELV were to be used to power the Orion capsule into orbit, there would be large parts of the trajectory where early aborts would cause loss of the capsule and crew during re-entry: the dreaded black zone. By adjusting the launch trajectory lower, these black zones can probably be eliminated -- but at a cost. The cost is performance: mass to orbit is decreased by flying a safer, more depressed trajectory.[/SIZE][/FONT]

[FONT=Verdana,Geneva,Arial,Helvetica,sans-serif][SIZE=-1]The shuttle flies a trajectory that is more depressed than expendible launch vehicles. This allows for potentially graceful abort trajectories following a premature engine shutdown.[/SIZE][/FONT].. [FONT=Verdana,Geneva,Arial,Helvetica,sans-serif][SIZE=-1]So the shuttle has a lot of capability compared with other rockets -- and a lot less capability than any capsules.[/SIZE][/FONT]

[FONT=Verdana,Geneva,Arial,Helvetica,sans-serif][SIZE=-1]As to why EELVs were not chosen by the Exploration team early on -- I don't think black zones had a lot to do with it, but I really don't know. I should ask and I will ask and I will report to you at a later day. However, the standard trajectory design for EELV launches would result in extensive black zones -- which can be either greatly reduced or eliminated by adjusting the trajectory -- which in turn leads to significant reductions in the mass which the EELV could place in orbit.[/SIZE][/FONT]

 

[Tschachim]

[FONT=Verdana,Geneva,Arial,Helvetica,sans-serif][SIZE=-1]As to why EELVs were not chosen by the Exploration team early on -- I don't think black zones had a lot to do with it, but I really don't know. I should ask and I will ask and I will report to you at a later day.[/SIZE][/FONT]

Well, that's interesting indeed, Jeff Hanley, now the Constellation program manager, said something different last month (and all the time before that): http://forum.nasaspaceflight.com/index.php?topic=14773.45

On EELV, because it won't be nearly the performer of Ares I, the abort problem would be much tougher. Harder nut to crack to get rid of black zones where abort is not possible.

As there's an ongoing discussion whether the ESAS was "dishonest" about the possibility to use EELVs in favor of ATK's SRM approach now called "Ares I", it would be interesting to know Wayne Hale's opinion about that...

Cheers
Tschachim

 

[movieman]

Except Boeing have already said they could eliminate all the 'black zones' on the Delta without a significant impact on payload...