RTLS Abort

blazingcessna · Apr 22, 2005

Can the shuttle actually do an RTLS? It seems that it would have to be at a high altitude before it could, otherwise there would be a new attraction on the beach. And if it was loaded fro bear, could you actually do a gear up belly landing?

SpaceKiwi · Apr 22, 2005

Theoretically, yes. However, it would be the highest of high-risk maneuvers and you would need to exhaust your entire lifetime's worth of good luck to pull it off I suspect. You have to wait until the SRB's have completed their burns, and then perform a powered pitch maneuver with ET to get headed back in the right direction. I believe this is the most dangerous part of the whole RTLS maneuver, and there is a good possibility you disintegrate at this point if the flight computers don't get it exactly right. I'm sure one of the experts will come in on this and confirm, but I doubt an Orbiter and crew would survive a gear-up landing due to the speed of approach and angle of attack to the runway. In that situation, I think the crew would rather take their chances bailing out (itself a highly dangerous maneuver). <div class="Discussion_UserSignature"> Who is this superhero? Henry, the mild-mannered janitor ... could be!-------------------------------------------------------------------------------------------Bring Back The Black! </div>

SpaceKiwi · Apr 22, 2005

SG, out of curiosity, do all Astronauts train for the bail-out maneuver on another aircraft, possibly configured with the correct diameter hatch in order to mimic the Orbiter as much as possible? <div class="Discussion_UserSignature"> Who is this superhero? Henry, the mild-mannered janitor ... could be!-------------------------------------------------------------------------------------------Bring Back The Black! </div>

ambrous · Apr 22, 2005

Where would the ET impact on the approach to KSC?

SpaceKiwi · Apr 22, 2005

I imagine that would depend on where they were trying to reach but, assuming you were trying to get back to KSC, as soon as the Orbiter got on the correct glide path with the correct velocity they would ditch the tank. So it would likely be in the Atlantic, many miles off the East Coast. I should say that might not be a huge amount of miles off the East Coast, as a RTLS action doesn't have the benefit of great height and great speed to play with as in a nominal return from orbit. <div class="Discussion_UserSignature"> Who is this superhero? Henry, the mild-mannered janitor ... could be!-------------------------------------------------------------------------------------------Bring Back The Black! </div>

najab · Apr 22, 2005

Out in the Atlantic, probably about 30-40 miles or so off the coast.

najab · Apr 22, 2005

>...as soon as the Orbiter got on the correct glide path with the correct velocity...Actually, in a RTLS abort the ET sep happens before the Orbiter is set up on the glideslope. At the time of ET sep the vehicle is back down in the atmosphere, and so the tank is separated (fast-sep) when they have enough airflow over the wings to fly properly. The Orbiter immediately has to pitch up to avoid recontacting the tank, then they can go about getting onto the glideslope.

SpaceKiwi · Apr 22, 2005

<img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> Who is this superhero? Henry, the mild-mannered janitor ... could be!-------------------------------------------------------------------------------------------Bring Back The Black! </div>

najab · Apr 22, 2005

>...as a RTLS action doesn't have the benefit of great height and great speed to play with...True, compared to return from orbit, but the problem with RTLS is actually too much height and particularly, too much velocity - in the wrong direction!!! The propellant dissipation phase of RTLS is all about killing the downrange velocity and getting the vehicle back into the atmosphere at a point from where it can glide back to KSC.

vogon13 · Apr 23, 2005

RTLS, risky as it is, would have been the only chance to get Columbia back. Re-entry heating for TAL is greater than a convential return to Edwards, or the cape. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Apr 23, 2005

Yeah, the what-ifs will drive you over the edge if you let them. A stand of silica fiber optics under the RCC, a photo cell,and a buzzer and the crew and gound control would have known.... <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

blazingcessna · Apr 23, 2005

I know the Orbiter has the aerodynamic characterstics of a pair of pliers, but I have always thought that any hard manuvers would snap the orbiter in half, specially if it is loaded heavy.

najab · Apr 23, 2005

For an ISS mission, the 'preferred' abort site is up the East coast, rather than back to the Cape. I can't remember where, but I once found a list of East Coast abort sites, it included one of the New York airports (I think it was JFK)! That would be something to see, an Orbiter gliding over NYC!

blazingcessna · Apr 24, 2005

I guess you all liked the opening of "The Core" with shuttle landing in the Los Angeles River!

SpaceKiwi · Apr 24, 2005

Hey, now that one must be true .... Hilary Swank can do anything, don't cha know! <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> Who is this superhero? Henry, the mild-mannered janitor ... could be!-------------------------------------------------------------------------------------------Bring Back The Black! </div>

steve82 · Apr 24, 2005

As many years as they've been practicing that maneuver, they could probably pull it off provided that all of the orbiter systems needed for it were working perfectly. The big question that's been surrounded by a lot of superstition over the years is whether they would ever push that little red button to invoke the BFS software.

najab · Apr 24, 2005

Did it scrub the launch, or were they brought back online in time?

steve82 · Apr 24, 2005

Ah, but would you pull the reserve if the main just didn't seem to be working right? Part of the reason for BFS was in case there was a generic problem in the PASS software. Some of the kinds of problems that could make PASS go down while not killing off a GPC would include things such as bad I-loads causing numerical integrators to diverge during a time critical portion of the flight, etc. Some of these failures can be very subtle yet still produce catastrophic results. As far as my observation about the orbiter working perfectly, I did qualify that with "all of the orbiter systems needed for it were working perfectly" Yep, the catch-22 of RTLS. Although there are some conceivable scenarios, say a massive ECLSS failure very early on, while all of the engines and GN&C and what not were working, that might lead to such a possibility. Now take your meds and lay off the caps.

najab · Apr 24, 2005

I'm sure that any time the crew or the ground don't like the numbers they are seeing, they'd push the button. As I'm sure you're aware, they have cue-cards onboard which tell them what they should be seeing during ascent and landing. If there was a serious deviation, and the BFS numbers were correct - the button gets pushed.I have to ask, however, how would the dolilu get messed up? When the crew is given the updated values they read them back, and enter them, then verify that they are correct. It would take a really convoluted set of screw-ups for the wrong values to be entered.Oh, btw, "Now take you meds and try using some whitespace."

steve82 · Apr 24, 2005

"I have to ask, however, how would the dolilu get messed up?" There are other Iloads besides the day-of-launch I-load update (dolilu). We have one specific case on record where a rendezvous targetting scheme failed to converge because the convergence limit (an I-load value) was incorrect for the range of the problem. If it were in a higher stress situation, say during powered flight in the atmosphere, that sort of failure- failure to converge, a trig function singularity, or any of a number of other possibilities- would have resulted in loss of the vehicle.

teije · Apr 25, 2005

Question about some of the acronyms in this thread. What are: BFS? GPC? PASS? forgive my ignorance and thanks in advance! <img src="/images/icons/smile.gif" /> Teije

teije · Apr 25, 2005

Thank you. So the BFS is used only in abort modes? RTLS, TAL, etc? Is there 'normal' backup of the PASS software as well?Also, you were talking about GPC 5 containing the BFS. Am I right in assuming that there are 4 normal GPC's? And do these work together, or are they redundant systems? The 'red button' that keeps being the discussion here. Is it only at mission control? Or in the orbiter itself as well? If someone presses it. Does BFS choose a flightpath? Or is this up to the commander/mission control? Quite a lot of questions. Sorry. <img src="/images/icons/smile.gif" /> Teije

najab · Apr 25, 2005

>The BFS software is not the same as the PASS software.It also isn't as...what's the word....refined. Compare it to AGS and PNGs in the Apollo LM - you could land on AGS if you had to, but all things considered, PNGs was your preference. In the same way, the BFS will get you to orbit, but it might probably won't be as accurate an insertion as PASS would achieve.

holmec · Apr 25, 2005

SG, what are the chances of surviving in maneuvers like this? Wheather it be attempting to land with the shuttle or bailing out. <div class="Discussion_UserSignature"> "SCE to AUX" - John Aaron, curiosity pays off </div>

teije · Apr 26, 2005

So from najaB's post my layman's conclusion is that BFS is kind of a 'safe mode' to PASS? But if they want to delete it and upgrade it with PASS, how can the STS fly on only 1 GPC instead of 4? And, another question. If the 'red button' is in the cockpit, is it only up to the commander/pilot to press it? Or can the call be made by mission control? Thanks, Teije

RTLS Abort

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