RTLS Abort

[najab]

Each of the 5 GPC's can fly the vehicle by itself. What they do is run the same software, using the same inputs on 4 of them in tandem. If the results from one of them don't match the other three, that one is considered failed and is taken out of service. The 5th one runs the BFS.

 

[najab]

One example that just came to mind to demonstrate the difference between the PASS and BFS software: SRB separation. PASS monitors the pressure transducers in the SRBs and initiates separation when the pressure drops below a fixed level. BFS initiates SRB sep at T+2:xx (I can't remember the exact time) - after all, they couldn't still be burning, could they?<p>shuttle_guy told us once that in a launch-day sim, there was an RSLS abort at T-0:01, but the BFS didn't halt, it was still running (and believed the vehicle was flying). They had to spot that, and disable it before it separated the SRBs <b>on the pad</b>!!!</p>

 

[teije]

That would have been a big 'oops'.... Good thing it was a sim!<br /><br />Thanks guys! I'm learning a lot here! <img src="/images/icons/smile.gif" />

 

[najab]

Now that I think about it some more, wasn't it that the GPCs had inhibited the ignition command to the SRBs for some reason? So the clock actually did hit zero.

 

[georgeniebling]

So ... what would happen if the ignitor was not stopped and:<br /><br />SSMEs were shutdown in a RSLS abort but the SRBs ignited ....<br /><br />

 

[georgeniebling]

if I'm reading this correctly ... the SRBs could have seperated from the stack *on the pad* .... as in .... there would have been video footage of the SRBs falling to the sides of the stack on the pad ....<br /><br />wow, THAT would be a PR nightmare ....<br /><br />"no, really ... it was a minor glitch, nothing to see here"

 

[nacnud]

I think that the SRBs are taking the weight of the ET and orbiter on the pad so rather than the SRBs falling to the sides the ET and orbiter would drop down. <img src="/images/icons/crazy.gif" />

 

[henryhallam]

I think this would be unlikely as the SRBs are ignited by the RSLS only once all SSMEs are confirmed as running and properly functioning (as far as I'm aware). If it did happen I would imagine it might be survivable for the crew - the shuttle will liftoff on SRB thrust alone, when they've burned out the crew can bail out. However there is the risk of propellant umbilicals being ripped open during the unwanted launch and I suppose something nasty could happen there.

 

[georgeniebling]

oh good God .... obviously the damage (total destruction of the stack, the pad, and a certain perimeter around the pad and loss of life onboard and at KSC) would be horrible.<br /><br />That is why I was asking possible effects on the *other* pad .... I presume in that order of explosion most if not all the hard assets (both pads, VAB, LCC, etc) would be lost.

 

[drwayne]

Ben Rich has an account of some experiments that were done at the Skunk Works during the liquid hydrogen plane work they did. It sounds like they had quite a bit of *fun*.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[nacnud]

Yep, thats a big tempurature difference.

 

[najab]

><i>This was not a sim but a launch attempt for STS-64 in 1994.</i><p>I feel used and lied to. *sniff* <img src="/images/icons/laugh.gif" /></p>

 

[georgeniebling]

what aircraft is/was this done from?<br /><br />could they have tested this from Enterprise during one of the drop tests?<br /><br />and speaking of Enterprise ... couldn't Enterprise's landings be counted in the "successful landing" column of shuttle events? (yeah, I know .... I just like the old girl and enjoy remembering the test series)

 

[georgeniebling]

I'll clarify what I was referring to:<br /><br />what aircraft is/was this done from? (I meant the bail out tests you mentioned .... you said there had been test jumpers ... could they have tested the bailout from Enterprise or was this done from another aircraft?)<br /><br /><br />and speaking of Enterprise ... couldn't Enterprise's landings be counted in the "successful landing" column of shuttle events? (yeah, I know .... I just like the old girl and enjoy remembering the test series) :<br />(someone else had replied to my question about the number of Shuttle missions with the # for launches, # on-orbit, and # of landings ... I was curious if the Enterprise Approach Tests could becounted as SHuttle landings .....<br />

 

[drwayne]

When was the last time anyone was actually in the Enterprise while if was in the air (on the back of the 747)? The test series? Or did they let anyone ride in it when it was ferried around after that?<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[najab]

I seriously doubt they would let anyone ride in the Orbiter when it's on the SCA - there would be no quick way for them to get out if there was a major malfunction.

 

[drwayne]

I seriously doubted it to, but, well....funny things happen...<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[SpaceKiwi]

Do they still ferry Enterprise around? I thought she was parked up at the Smithsonian? <div class="Discussion_UserSignature"> <p><em><font size="2" color="#ff0000">Who is this superhero?  Henry, the mild-mannered janitor ... could be!</font></em></p><p><em><font size="2">-------------------------------------------------------------------------------------------</font></em></p><p><font size="5">Bring Back The Black!</font></p> </div>

 

[georgeniebling]

najab suggested the danger is being in the Orbiter lest there be a major malfunction ....<br /><br />wouldn't it make sense to have someone in it (any Orbiter on the back of the SCA) lest a major malfunction occur so the Orbiter could be detached and a landing attempted?<br /><br />note: could the window covers be made .. eject-able?

 

[drwayne]

A few years ago the 747/orbiter flew right over us, near our home in Navarre, on its approach to overnight at Eglin. It sure made a lound and distinctive sound....of course, at that point it was pretty low too...<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]

To elaborate on post-ALT ferrying of Enterprise....<br /><br />Although it is pretty much a permanent Smithsonian fixture today, it did make some appearances at airshows in the years after its retirement, including a visit to the famous Paris Air Show. It rode on the back of an SCA for that. (Considering that using a 747 as an SCA really takes the vehicle to its limits, I have to be rather impressed that they managed a transatlantic crossing. I wonder if they had to stop in Iceland or someplace to refuel? I'm sure fuel consumption is a lot more dramatic in an SCA than in a typical passenger 747.)<br /><br />I read a fun article about SCA pilots once. One of them described it as flying the world's most sophisticated biplane. <img src="/images/icons/wink.gif" /><br /><br />My father-in-law got close to an SCA once, with a shuttle on the back. I'd have to ask my husband for details, but if memory serves, it was during the one-and-only stay of an actual space-worthy orbiter at a public airfield: Dallas/Fort Worth. My father-in-law (who provides base security for the USAF) was stationed in the vicinity at the time, and was part of the security detail assigned to watch over it while it was there. Very cool vehicle. <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>

 

[najab]

><i>Considering that using a 747 as an SCA really takes the vehicle to its limits, I have to be rather impressed that they managed a transatlantic crossing. I wonder if they had to stop in Iceland or someplace to refuel? I'm sure fuel consumption is a lot more dramatic in an SCA than in a typical passenger 747.</i><p>The main reason it's so dramatic is because it has to fly so low - 15,000 feet as opposed to 35,000 for a typical trans-Atantic flight. The reason it has to fly so low is to prevent the fluids freezing and bursting their lines. I asked shuttle_guy about the crossing to Paris, and he couldn't remember, but he was 95% sure that they did fly the Northern route and stopped in Iceland to refuel (not reprop in this case <img src="/images/icons/wink.gif" />).</p>

 

[drwayne]

I seem to recall in its post-flight-test years it also did some testing at various places, but my memory may be faulty...<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[najab]

It was used for fit checks at KSC and VAFB.

 

[drwayne]

Your answer still does not preclude faulty memory on my part! LOL at Wayne the old fart...<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>