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Author Topic:   Space shuttle main landing gear failure
ASCAN1984
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From: County Down, Nothern Ireland
Registered: Feb 2002

posted 09-01-2010 12:36 PM     Click Here to See the Profile for ASCAN1984   Click Here to Email ASCAN1984     Edit/Delete Message   Reply w/Quote
What would be the possibility of crew survivability if the main gear when lowered for landing failed?

mjanovec
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From: Midwest, USA
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posted 09-01-2010 01:36 PM     Click Here to See the Profile for mjanovec   Click Here to Email mjanovec     Edit/Delete Message   Reply w/Quote
The chances for survivability likely depend on the circumstances of the failure. Do both main gear fail to lower? Does the failure include the nose gear as well? Does only one main gear lower? Do both main gear lower but one or both fail to lock in place... or somehow fail to support the weight of the orbiter upon touchdown (perhaps after a hard landing)? Does the failure happen at touchdown or somewhere later during the rollout? Survivability may also depend somewhat on where the landing is taking place... KSC or Edwards.

I don't claim to know the answers to the above scenarios, though I have to assume only one main gear lowering might be worse than all gear failing to lower... since it rules out a textbook style belly landing. Then again, at the speed the orbiter is traveling at touchdown, I don't know how survivable a full gear-up belly landing is either.

Whatever the case, there is very little time to react to such a failure. Presumably the astronauts could have ejected from the shuttle during the first four test flights if the gear failed to deploy. That, of course, is no longer an option.

Jay Chladek
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From: Bellevue, NE, USA
Registered: Aug 2007

posted 09-12-2010 01:30 AM     Click Here to See the Profile for Jay Chladek   Click Here to Email Jay Chladek     Edit/Delete Message   Reply w/Quote
If the normal extension sequence doesn't take place, then the shuttle has a backup set of pyros that are designed to blow open the doors and extend the gear down and lock them into place.

The way the gears are designed with them folding back, if they get down part way, air drag will take them down the rest of the way to lock them into place.

Of course, at that point the pilots are on their own to essentially trust that the gear will be down and locked.

Other things could happen after touchdown, such as a tire blowing out or a brake locking up. Both happened on different shuttle missions, but usually after the rollout or at a slow enough speed so as not to cause any further problems.

Max Q
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From: Whyalla South Australia
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posted 09-12-2010 08:26 AM     Click Here to See the Profile for Max Q   Click Here to Email Max Q     Edit/Delete Message   Reply w/Quote
Has the shuttle ever blown a tire on landing?

GACspaceguy
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From: Guyton, GA
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posted 09-12-2010 08:58 AM     Click Here to See the Profile for GACspaceguy   Click Here to Email GACspaceguy     Edit/Delete Message   Reply w/Quote
STS-51D had a blown tire on roll out after landing. Here is the Youtube video of the liftoff and landing showing the tire blow.

Some reading I was doing indicated that nose gear steering was added to the Shuttle fleet after this incident. Prior to that was steering done via differential braking and was the use of differential braking a contributing factor resulting in a blown tire? Was there a significant cross wind for this landing? Looks like I have added more questions than answers to this thread.

moorouge
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posted 09-22-2010 03:25 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
My understanding of a landing gear failure is that it was considered to be a Critical One failure i.e. crew survival was problematical.

mto
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posted 09-23-2010 11:48 AM     Click Here to See the Profile for mto   Click Here to Email mto     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by GACspaceguy:
...was the use of differential braking a contributing factor resulting in a blown tire? Was there a significant cross wind for this landing? Looks like I have added more questions than answers to this thread.
Long time lurker and first time poster. There's an excellent series of lectures about the shuttle available for free at MIT OpenCourseWare. The lecture on Landing and Mechanical Systems (link) has a good description of the blow out on 51D by Dr. Jeffrey A. Hoffman who was part of the crew. The description begins at about the 1:13 mark in the mp3.

Differential braking due to the cross wind was indeed the cause. Nose wheel steering was available but was only 'single string' with no backup system and so was not normally used. A backup system and drogue chute added later eliminated the use of differential braking.

Jay Chladek
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From: Bellevue, NE, USA
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posted 09-24-2010 11:07 AM     Click Here to See the Profile for Jay Chladek   Click Here to Email Jay Chladek     Edit/Delete Message   Reply w/Quote
Another factor in the tire blowout was the way the KSC runway was grooved to facilitate water drainage during rain showers. Practically all heavy jet runways are grooved in this manner to help prevent hydroplaning if a jet has to land in rain. The runway was also crowned (i.e. the center of the runway sits slightly higher then the edges) for drainage purposes as well (same as a two lane highway). The drainage grooves cut in the runway put excessive wear on the tires and the crosswind blew the shuttle off centerline at touchdown, so it was trying to correct "uphill" as it were and that stressed the tires a bit too much.

As for brake lockup, the shuttle's beryllium brakes in the original design were prone to it. Indeed one of the early Challenger landings at Edwards had that problem and it was a bit of a puzzle to figure out how to pull the brake off one wheel set while it was on the runway. Beryllium is also a toxic metal if inhaled, so precautions had to be taken to avoid that problem as well. The brakes were eventually replaced with units that used carbon pads and they haven't been a problem since then. Of course, the drag chute also helps.

Hart Sastrowardoyo
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From: Toms River, NJ
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posted 09-24-2010 11:16 AM     Click Here to See the Profile for Hart Sastrowardoyo   Click Here to Email Hart Sastrowardoyo     Edit/Delete Message   Reply w/Quote
I always believed that the brake lockups - and maybe the tire blowouts - were due to the original weights of the orbiters. That is, they had wanted to build an 150,000 pound orbiter (although I'm unsure as to whether or not that's 150,000 pounds total or without main engines installed) and in the case of at least Columbia, wound up with an 182,000 pound or so orbiter.

ASCAN1984
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From: County Down, Nothern Ireland
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posted 09-24-2010 11:38 AM     Click Here to See the Profile for ASCAN1984   Click Here to Email ASCAN1984     Edit/Delete Message   Reply w/Quote
In the case of STS-107, has it ever been discussed what Columbia's flight controllers were thinking of doing with the tire pressure messages? If Columbia had survived reentry what would have happened for landing? Would we have seen the first shuttle bail out?

ilbasso
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From: Greensboro, NC USA
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posted 09-24-2010 01:03 PM     Click Here to See the Profile for ilbasso   Click Here to Email ilbasso     Edit/Delete Message   Reply w/Quote
I've wondered that about STS-107, too. But in watching the video of Mission Control during the final minutes, and you don't see orders being given to prepare for that contingency. I wonder how fast the bail-out procedure can be executed from the time it is called?

Obviously they needed to gather more info before committing to a course of action which would have meant certainly losing the vehicle in exchange for (probably) saving the crew.

Hart Sastrowardoyo
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From: Toms River, NJ
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posted 09-24-2010 01:16 PM     Click Here to See the Profile for Hart Sastrowardoyo   Click Here to Email Hart Sastrowardoyo     Edit/Delete Message   Reply w/Quote
My understanding is that the STS-107 crew was too high (and flying too fast) for a bailout. A bailout was optimal if the shuttle was on final approach (maybe if they had the runway in sight or was on one of their HAC swings?)

Skylon
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posted 09-24-2010 06:26 PM     Click Here to See the Profile for Skylon     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by ASCAN1984:
In the case of STS-107, has it ever been discussed what Columbia's flight controllers were thinking of doing with the tire pressure messages? If Columbia had survived reentry what would have happened for landing? Would we have seen the first shuttle bail out?

I do not recall if it was determined (when the tire pressure sensor went off) if that was due to bad sensor data as a result of hot plasma wreaking havoc with the sensors in Columbia's wheel well, or if the tire actually had low pressure prior to orbiter breakup. I think the former.

Had Columbia survived longer, no doubt the MCC team would have worked to determine if the tire pressure warning was instrumentation or a reality.

mjanovec
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From: Midwest, USA
Registered: Jul 2005

posted 09-25-2010 03:10 AM     Click Here to See the Profile for mjanovec   Click Here to Email mjanovec     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Hart Sastrowardoyo:
My understanding is that the STS-107 crew was too high (and flying too fast) for a bailout. A bailout was optimal if the shuttle was on final approach (maybe if they had the runway in sight or was on one of their HAC swings?)

I think you misunderstood ASCAN1984's question. I believe he was asking about preparing to bailout while Columbia was near KSC (if tire pressure had truly been the only issue at hand). I don't think he was talking about bailing out over Texas, where the tragedy occurred.

I concur with Jonathan (ilbasso) that it appears bailout was not something that was given any discussion (at least on the voice loops) after the tire pressure messages were received from Columbia. But I suspect that more than a few people in Houston suspected there was a deeper issue at play than just tire pressures.

Skylon
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posted 09-25-2010 07:39 AM     Click Here to See the Profile for Skylon     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by mjanovec:
I concur with Jonathan (ilbasso) that it appears bailout was not something that was given any discussion (at least on the voice loops) after the tire pressure messages were received from Columbia. But I suspect that more than a few people in Houston suspected there was a deeper issue at play than just tire pressures.
First of all, I don't think there was time. The tire pressure message was not long before loss of contact.

Second, I'd agree the MCC team was likely focused on more than the tire pressure message, as the off-scale low sensors with "no commonality" had been announced over the voice loop, and was being looked at. The tire pressure was probably seen as tied to that systemic problem with the sensors that had been observed.

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