Returning aborted Orbiter to KSC

[Squid.erau]

Ikelos - 5/7/2007  1:38 PM

What about an F-18 as a refueler?

Unless my math is really off, a fully fueled F/A-18E with 4 external tanks has enough fuel to get the SCA about 114 miles.  And that's completely draining the F-18.  So yeah, it would take a lot of refuelings

Matt

[Ikelos]

Even if you give half the F-18's fuel, do four refuels thats ~200 miles, given the altitude and speed it could be done at close to the 747's cruise probably. Plus refueling the F-18 in air is not a problem at all. And 200 extra miles could mean quite a bit, or if need be, you could keep refueling over and over from a tanker to F-18 to 747.  I just think this is a doable situtation, maybe with a different small plane or something though.

[SpaceNutz SA]

Which raises the question - how many of these emergency situations does the crew train for because it seems like there are a lot of them.  Does the shuttle have all of these scenarios on-board or do they get up-linked as the situation unfolds?

[psloss]

Paging Jorge...FWIW, here's something he posted over on Usenet a little while ago (almost 7 years ago):
http://groups.google.com/group/sci.space.shuttle/browse_thread/thread/17c5fbe68003740/bcfb9f0c86220507

[Jorge]

psloss - 5/7/2007  3:02 PM

Paging Jorge...FWIW, here's something he posted over on Usenet a little while ago (almost 7 years ago):
http://groups.google.com/group/sci.space.shuttle/browse_thread/thread/17c5fbe68003740/bcfb9f0c86220507

Some things have changed in the last seven years but the broad outline is similar to what I wrote then.

The biggest change is the availability of CSCS (Contingency Shuttle Crew Support aka "safe haven") on ISS, followed by a LON (Launch On Need) rescue flight, as an alternative to performing a JEUS (Joint Expedited Undocking and Separation) followed by an emergency deorbit and landing.

This is not always a slam-dunk decision. The LON need-date is driven by the CSCS duration, and that duration is in turn driven by the amount of shuttle consumables available. To maximize CSCS duration, the shuttle crew first scavenges all available shuttle consumables, then once the orbiter is depleted (~23 days) performs an unmanned undocking/disposal of the crippled orbiter and relies on ISS consumables until the LON flight arrives. And of course there is the risk of committing a second shuttle/crew to a LON when the root causes of the failure on the original orbiter are unsolved.

Some emergency scenarios limit the shuttle consumables available. For example, loss of both Freon loops will cause the loss of all three fuel cells within a matter of hours, and once that happens, the fuel cells will no longer be able to generate water. That in turn will severely limit the CSCS duration should the shuttle crew stay aboard ISS rather than attempt an immediate JEUS/emergency deorbit. So in this scenario (or anything similar, like an orbiter cabin leak), MCC must make the JEUS vs CSCS/LON decision very quickly, based on limited data.

NASA has largely chosen to mitigate this risk by minimizing exposure. Flight Rules call for terminating the flight at the next Primary Landing Site (PLS) if one of the two Freon loops fails, for example. Radiator bypasses have been installed to prevent a MMOD strike on a radiator from depleting the associated Freon loop, as well.

On the other hand, more complications have arisen as ISS assembly continues. The original shuttle Emergency Separation procedure made no effort to protect the station from RCS plume impingement. That was acceptable in the early days when ISS was unmanned but now it carries the potential of rendering the station uninhabitable while simultaneously damaging the station crew's Soyuz escape vehicle beyond use. So the procedure has been modified to be "station friendly". It turned out to be impossible to do this while allowing safe separation from all combinations of orbiter/ISS stack attitudes, so the procedure was modified to maneuver the stack to one of two analyzed undocking attitudes first. This wound up not to be much of a net time hit since it could be performed in parallel with the Joint Emergency Egress, which requires some time to perform anyway.

Another complication has been the added requirement for "critical feathering" of ISS solar arrays as part of the JEUS. As solar arrays have been added outside the alpha joints on recent assembly flights, the station's vulnerability to RCS plume impingement has increased. Excessive RCS structural loads on unfeathered arrays can cause the SAW masts to buckle, turning the outboard blanket boxes/mast cannisters into something akin to a sledgehammer that could swing around and strike the pressurized modules. When the JEUS was first modified to accommodate this, the time required to get to undocking shot up to nearly 50 minutes. This was unacceptable and resulted in some serious negotiations about what was truly "critical". In the end, the feathering was split into three categories: that required prior to maneuvering to undock attitude, that required prior to undocking itself, and finally the nice-to-have. That last really caused some teeth-gnashing - of course it was all "critical", otherwise the ISS folks wouldn't have put it in the procedure in the first place, would they? - but eventually things got sorted out. Careful optimization of the procedure to allow maximum parallel activity by the ISS crew, shuttle MSes, and shuttle CDR/PLT got the time required to undock back down into the low 20s, and that with an untrained two-man shuttle crew. A full trained (and highly motivated, on the real day!) crew could of course do better.

In the end, JEUS/emergency deorbit vs CSCS/LON is a risk-vs-risk tradeoff that will require a lot of real-time decision making if one of these scenarios ever occurs. Flight Rules can reduce the amount of real-time rationalization but there are simply too many scenarios to try to write rules to cover them all. The Flight Rules provide a good playbook but MCC and the crew will still wind up doing a lot of improvised broken-field running when the play breaks down.

[brahmanknight]

Wow, Jorge!  That is the kind of analysis that I joined this site for.  I had no idea the SAWs could bend that far.  So does this mean that we are looking at about about an hour between decision and landing?  Somewhere around 20-30 minutes to undock, and 45 for deorbit?

[sbt]

Briefly returning to the original subject...

Would it be possible and/or advantageous to use the An-225 to retrieve a 'Landed Away' Orbiter? I'm presuming an adaptor for the Buran mounting points would be required which might reduce range unacceptably.

Rick

[Jim]

sbt - 8/7/2007  11:15 AM

Briefly returning to the original subject...

Would it be possible and/or advantageous to use the An-225 to retrieve a 'Landed Away' Orbiter? I'm presuming an adaptor for the Buran mounting points would be required which might reduce range unacceptably.

Rick

What says the range on the An-225 is any better (even without an adaptor)?  Also how would the combination be flight tested?  Buran tests would not be enough.

And why bother, the chances are remote

[Jorge]

brahmanknight - 8/7/2007  9:59 AM

Wow, Jorge!  That is the kind of analysis that I joined this site for.  I had no idea the SAWs could bend that far.  So does this mean that we are looking at about about an hour between decision and landing?  Somewhere around 20-30 minutes to undock, and 45 for deorbit?

About 2 hours. 20-30 from decision to undock, 30 from undock to deorbit TIG, and 60 from deorbit TIG to wheels stop.

That doesn't allow much of a deorbit window, so in the 2-hour case it's probably going to end in bailout rather than wheels stop.

OTOH, two hours to the ground is just the design case for the JEUS/Emergency Sep/Emergency Deorbit, driven by the "simultaneous loss of both Freon loops" scenario. Most scenarios allow more time.

[sbt]

Jim - 8/7/2007  4:42 PM

sbt - 8/7/2007  11:15 AM

Briefly returning to the original subject...

Would it be possible and/or advantageous to use the An-225 to retrieve a 'Landed Away' Orbiter? I'm presuming an adaptor for the Buran mounting points would be required which might reduce range unacceptably.

Rick

What says the range on the An-225 is any better (even without an adaptor)?  Also how would the combination be flight tested?  Buran tests would not be enough.

And why bother, the chances are remote

Well the payload at longer ranges (TBH, at any range) is significantly greater for the An-225 vs a B747. Whilst such things depend on the exact shapes of the payload range curves and the weight involved, at high payload weight that usually translates into greater range, although in this case drag might negate the advantage.

In an impossible situation range-wise for the SCA the An-225 MIGHT be an option.

Why not any other aircraft? - The An-225 was designed to carry external loads, not just Buran (specifically Launcher Stages but it has carried non-aerospace loads) and the SCA and the old Bison carrier are the only other aircraft set up for this.

As for flight test, I would presume that this would be a unique flight (or flights) cleared by analysis and with basic handling checks carried out within range of the departure airfield and appropriate manoeuvre limits imposed. I assume the analysis would be less onerous than for the SCA due to there being no fin or rudder behind the load on the An-225 and less difficult than from scratch due to the previous work on Buran and other loads.

As to why? - Because the remote chance had happened. Or are you saying NASA would just leave the Orbiter where it was rather than consider using a non-US asset?

To be clear, I was asking for more informed opinion on the pro and cons of this remote chance and hoping that I might thereby learn something.

BTW, thinking about the shipping option I briefly considered the implications of vessels other than a CVN before realising that this was the best option with regard to speed and power to avoid weather issues and to, if this failed, to limit accelerations on the Orbiter[1] (somewhere I encountered a source for accelerations on the contents of a container when the ship 'slams' - not good!). OTOH a (pretty solid) deck shelter would probably have to be constructed. I presume that salt water corrosion would not be much of an issue as dry air would be rigged up and the Orbiter was designed to survive the salt laden atmosphere on the pad.

Rick

[1] Size reduces motion due to weather in ships, plus Carriers are designed to have have long roll and pitch periods which eases flying operations and reduces the accelerations due to rapid righting seen in 'stiff' ships.

[Jim]

There are no impossible range solutions.
It isn't the weight that is the issue, it is the max altitude restriction imposed by the fluids on the orbiter.  This is what limits the SCA range.  A fully loaded B747 weighs more than the SCA with orbiter on it

"As for flight test, I would presume that this would be a unique flight (or flights) cleared by analysis and with basic handling checks carried out within range of the departure airfield and appropriate manoeuvre limits imposed"
Still wouldn't happen, still too much risk, and there would be other work arounds

And considering that such an event would end the shuttle program, it might be left there.

Also by the time an adapter could be built, the orbiter would moved by other means

[Jorge]

sbt - 8/7/2007  6:37 PM

Jim - 8/7/2007  4:42 PM

sbt - 8/7/2007  11:15 AM

Briefly returning to the original subject...

Would it be possible and/or advantageous to use the An-225 to retrieve a 'Landed Away' Orbiter? I'm presuming an adaptor for the Buran mounting points would be required which might reduce range unacceptably.

Rick

What says the range on the An-225 is any better (even without an adaptor)?  Also how would the combination be flight tested?  Buran tests would not be enough.

And why bother, the chances are remote

As to why? - Because the remote chance had happened. Or are you saying NASA would just leave the Orbiter where it was rather than consider using a non-US asset?

No, I think what he's saying (and if it is what he's saying, I agree) is that if an orbiter ever had to perform a TAL or otherwise non-CONUS landing, at this point in the program, it would be the last flight of that orbiter. So the orbiter would be returned to the US, but there is no need to return it quickly in one piece, since it is going to a museum anyway. Disassemble it at the TAL site, barge the pieces back by slow boat, and reassemble the orbiter at the museum.

[elmarko]

Speaking of elaborate refuelling in the air, this would seem to be a fun thing to post, although very off-topic:

http://www.raf.mod.uk/falklands/bb.html

The ridiculously well-planned refueling operation for the first bombing raids during the Falklands War. Those Vulcans were hungry beasts...

[Danny Dot]

Jim - 8/7/2007  7:46 PM

There are no impossible range solutions.
It isn't the weight that is the issue, it is the max altitude restriction imposed by the fluids on the orbiter.  

snip

Is it the water in the orbiter that doesn't like the altitude?  I assume the problem is the fluid freezes.  I have often wondered about the altitude restriction on the SCA.  I find it ironic that a vehicle designed to go into space, has to be ferried at a low altitude.

Danny Deger
http://www.dannydeger.net