Shuttle Fleet Grounded Indefinitely

[RThurmont]

Orbiter age is undeniably a long-term problem, but it didn't cause the loss of Columbia in 2003, and it was not responsible for the near-disaster on the current mission. I don't deny that the orbiters will at some point have to be replaced, but I think they are a long way from reaching that state.

In the aviation world, aircraft typically operate for 50,000 hours or so before receiving a D-check (a complete inspection and possible repair to the structure of the airframe), and can operate for decades before reaching the design limit (a pressurized aircraft can only be safely pressurized and depressurized so many times before the structure is comprimised).

The space shuttles, if they were airliners, wouldn't be even close to needing a D-check, let alone replacement. Now I recognize that the orbiters do undergo much greater stress than any aircraft we have down below. That said, they're also used far less, and are maintained far more extensively. They undergo extremely heavy D-check style maintenance between every flight. So far, we've yet to hear any report from NASA that they are worried about the age of the orbiters.

The problem is with the external fuel tank, and that much is obvious. The real question is, can NASA create a solution to obviate the risk of the orbiters being struck by stray foam?

[Broomstick]

Aluminum has the wonderful feature of being strong and light. It also has features that make it less than ideal in a high heat or high stress situations.

Steel might withstand repetitive stresses better, but it's too heavy to use as the airframe for the shuttles.

And even if it was light enough - steel can break under repetitive stress, too - I've seen it in aircraft before. If anyone is really interested in observing this you can probably go down to your local small airport and ask to see some busted parts. If there's a shop there that does helicoptor maintenance they should have no problem showing you stuff like that.

And before anyone brings up the composite argument - they have failure modes, too. I've seen composite props withstand all sorts of abuse, then shatter at the next ding. Composites can fail with no warning at all, or at least with no warning we're able to pick up at present. Steel, aluminum, wood, and cloth all show signs of wear if you bother to look, composites are more problematic that way.

ALL aerospace designs are a compromise, there are no ideal materials, they all have good points and bad points. Which is why anything that flies any distance needs maintenance and inspection.

As pointed out, the airframes have had nothing to do with the two shuttles lost. Sponteneous in-flight structural failures have gotten progressively rarer in the past half-century, which may tie in to why it was a frozen o-ring or busted heat tile that brought down the lost shuttles rather than a wing snapping off due to aerodynamic pressures.

The problem is that ANY flying machine is a complex system of the sort where a minor defect in a "minor" part can set off a chain of events that leads to catastrophic failure.

[RThurmont]

Well they're now talking about this grounding not being nearly as long in duration as the previous one, and there are even hopes that Atlantis will be able to get off the ground before the end of the year. There seems to be a firm commitment on the part of NASA to finish the ISS and to finish the space shuttle program, so we should probably discard any notions of early retirement at this point in time.

Unless in the coming weaks NASA discovers massive technical problems that can't be solved, I see the shuttles remaining in service as planned, albeit with a slight delay while this stray foam problem is corrected.

[WyrdNyrd]

According to earlier posts in this thread:

• A crew of four is all that's needed to get the Shuttle up and back again.
• Getting all 7 down again will be difficult, requiring 2 or 3 Shuttle trips, or 4 Soyuz trips, if the Shuttles can't fly anymore.

Doesn't that beg the question, "Why did they send a full crew of seven in the first place?"

Were all 7 really necessary? I though the main point of this flight was to test the improvements, with re-supplying the ISS as secondary. To fill the damned thing to capacity, despite not having tested the fixes, smacks less of confidence than of downright hubris.

Or am I missing something?

Oh, and now they're worried about protruding gap filler. At least it seems that the falling foam didn't cause any damage this time after all.

Shuttle managers are still deciding whether to send an astronaut to Discovery's underside to deal with material, or gap filler, that is sticking out between tiles in two places on the orbiter's underside.

"We have a team of folks working aggressively to go and make that gap filler safe if we decide it's an issue. We have a separate team looking at the effects of leaving that gap filler protruding," mission flight director Paul Hill said on Sunday.

'Russian roulette'

Any material dangling from the shuttle could increase heating on tiles downstream of it as Discovery re-enters Earth's atmosphere.

Any repair would most likely take place on the third and final planned EVA of the mission, which occurs on Wednesday.

[TimothyC]

According to earlier posts in this thread:

• A crew of four is all that's needed to get the Shuttle up and back again.
• Getting all 7 down again will be difficult, requiring 2 or 3 Shuttle trips, or 4 Soyuz trips, if the Shuttles can't fly anymore.

Doesn't that beg the question, "Why did they send a full crew of seven in the first place?"

Were all 7 really necessary? I though the main point of this flight was to test the improvements, with re-supplying the ISS as secondary. To fill the damned thing to capacity, despite not having tested the fixes, smacks less of confidence than of downright hubris.

Or am I missing something?

According to this the shuttle can bring down 11 people in a pinch.

Skylon's original post that included said link here.

[Firefox]

Were all 7 really necessary? I though the main point of this flight was to test the improvements, with re-supplying the ISS as secondary. To fill the damned thing to capacity, despite not having tested the fixes, smacks less of confidence than of downright hubris.

Yes, all seven were needed. The pilot, commander and flight engineer are not normally trained to perform EVAs -- that's the job of the payload and mission specialists, depending on the mission. And as far as EVAs are concerned, two astronauts are required to go at a time for safety reasons. The other two crew monitor their progress, and are trained to operate the RMS and perform other payload-related functions.

As for how easy it is to bring back seven astronauts from a wounded bird, Maurius explained that.

[Skylon]

Yes, all seven were needed. The pilot, commander and flight engineer are not normally trained to perform EVAs -- that's the job of the payload and mission specialists, depending on the mission. And as far as EVAs are concerned, two astronauts are required to go at a time for safety reasons. The other two crew monitor their progress, and are trained to operate the RMS and perform other payload-related functions.

Just to note, The Flight Engineer on this mission also was on the EVA crew (Steve Robinson, who just yanked that gap filler piece out). The Flight Engineer is generally picked by the Commander, whichever Mission Specialsit in the crew, the Commander feels is most familiar with the orbiter's systems. Their job is really more reserved for launch and entry and keeping the Commander and Pilot on track, following the timeline and sequence of events so they can do what they need to.

EVA's are also rather physically taxing proceedures and can leave someone pretty drained. Hence why the extra hands are usually around.

This flight is also busy as hell with all the inspections of the TPS.