Author Topic: NASA class MMOD as primary threat to commercial crew vehicles  (Read 34800 times)

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 28853
  • Minnesota
  • Liked: 9044
  • Likes Given: 5798
Dragon already contains strain gauges. Getting shot by a bullet should be detectable without 500lbs of wiring.
Sure, if you hit really close to a strain gauge and do a lot of damage.  Otherwise, they're useless for this....
If a huge MMOD hit Dragon, enough to fatally damage it, it would ring like a bell, like getting shot be a gun. You would hear it, and sound waves can be (and are) picked up by strain gauges. It may not be precise, but knowing that it happened would be useful info.

If a huge MMOD (hint: what does the first M stand for?)
huge being relative, of course. It'd have to be huge to make any fatal damage.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Online abaddon

  • Full Member
  • ****
  • Posts: 1804
  • Liked: 1320
  • Likes Given: 1298
That was used for ascent purposes and was designed [...]
That's a lot of words rather than just admitting you're wrong.  That doesn't mean it was perfect or even worthwhile, but a spacecraft has indeed used such a system.
Quote
your mass budget is much better spent making the vehicle itself less vulnerable to damage than it is trying to pinpoint where it did get hit.
That's a perfectly reasonable argument.

Online SWGlassPit

  • I break space hardware
  • Full Member
  • ****
  • Posts: 620
  • Liked: 522
  • Likes Given: 75
Did you read the minutes?  NASA wants the requirement to be met without requiring inspection.

I got that. Are you saying, NASA won't agree to inspections when they know, there is something wrong? Just insisting it is the sole problem of the contractor? Seriously?

I'm almost positive that they'll do inspections anyway.  The inspections, however, can't be part of the path to meeting requirements.  The vehicles have to do that by themselves.

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 28853
  • Minnesota
  • Liked: 9044
  • Likes Given: 5798
Did you read the minutes?  NASA wants the requirement to be met without requiring inspection.

I got that. Are you saying, NASA won't agree to inspections when they know, there is something wrong? Just insisting it is the sole problem of the contractor? Seriously?

I'm almost positive that they'll do inspections anyway.  The inspections, however, can't be part of the path to meeting requirements.  The vehicles have to do that by themselves.
So in other words, compound conservatism. Sounds like a good recipe to increase overall costs.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Online SWGlassPit

  • I break space hardware
  • Full Member
  • ****
  • Posts: 620
  • Liked: 522
  • Likes Given: 75
That was used for ascent purposes and was designed [...]
That's a lot of words rather than just admitting you're wrong.  That doesn't mean it was perfect or even worthwhile, but a spacecraft has indeed used such a system.

It's not the same system.  It wasn't designed to be used to detect MMOD strikes, and -- surprise -- it didn't do a good job of doing so.  No human spacecraft has flown with an MMOD strike detection system.

Online SWGlassPit

  • I break space hardware
  • Full Member
  • ****
  • Posts: 620
  • Liked: 522
  • Likes Given: 75
Did you read the minutes?  NASA wants the requirement to be met without requiring inspection.

I got that. Are you saying, NASA won't agree to inspections when they know, there is something wrong? Just insisting it is the sole problem of the contractor? Seriously?

I'm almost positive that they'll do inspections anyway.  The inspections, however, can't be part of the path to meeting requirements.  The vehicles have to do that by themselves.
So in other words, compound conservatism. Sounds like a good recipe to increase overall costs.

If you already have the assets and the capability to do a photographic inspection on orbit prior to or just after departure, why wouldn't you?  They did it for Shuttle, they did it for Soyuz.  All things told, the cost of doing the imagery vs not doing the imagery is minor.  What NASA is saying is "no, you can't skimp on shields by saying 'oh, they'll just catch it with imagery once we're up there.'  Your spacecraft has to be safe even without imagery."

Online Hobbes-22

  • Full Member
  • ****
  • Posts: 466
  • Acme Engineering
    • Acme Engineering
  • Liked: 164
  • Likes Given: 109
Dragon already contains strain gauges. Getting shot by a bullet should be detectable without 500lbs of wiring.
Sure, if you hit really close to a strain gauge and do a lot of damage.  Otherwise, they're useless for this....
If a huge MMOD hit Dragon, enough to fatally damage it, it would ring like a bell, like getting shot be a gun. You would hear it, and sound waves can be (and are) picked up by strain gauges. It may not be precise, but knowing that it happened would be useful info.

ISTR astronauts saying they could hear MMOD strikes on the ISS. That suggests non-fatal hits can be picked up by microphones. Spread a few along the main structures and triangulate to find the source, that should take far less than 500 lbs.

Online SWGlassPit

  • I break space hardware
  • Full Member
  • ****
  • Posts: 620
  • Liked: 522
  • Likes Given: 75
Dragon already contains strain gauges. Getting shot by a bullet should be detectable without 500lbs of wiring.
Sure, if you hit really close to a strain gauge and do a lot of damage.  Otherwise, they're useless for this....
If a huge MMOD hit Dragon, enough to fatally damage it, it would ring like a bell, like getting shot be a gun. You would hear it, and sound waves can be (and are) picked up by strain gauges. It may not be precise, but knowing that it happened would be useful info.

ISTR astronauts saying they could hear MMOD strikes on the ISS. That suggests non-fatal hits can be picked up by microphones. Spread a few along the main structures and triangulate to find the source, that should take far less than 500 lbs.

If that even works (signal-to-noise ratio issues abound here), what would that accomplish?  You look at it and go, "yep, that's a strike."  Then what?

Online guckyfan

  • Senior Member
  • *****
  • Posts: 6939
  • Germany
  • Liked: 1906
  • Likes Given: 1969

Online SWGlassPit

  • I break space hardware
  • Full Member
  • ****
  • Posts: 620
  • Liked: 522
  • Likes Given: 75

Online obi-wan

  • Full Member
  • **
  • Posts: 295
  • Liked: 630
  • Likes Given: 13
MMOD = Micro-Meteoroid and Orbital Debris

Online docmordrid

  • Senior Member
  • *****
  • Posts: 5456
  • Michigan
  • Liked: 2845
  • Likes Given: 1

What's next after that?

Open a bagged cola and watch it stream to the hole? /ducks/
DM

Online Hobbes-22

  • Full Member
  • ****
  • Posts: 466
  • Acme Engineering
    • Acme Engineering
  • Liked: 164
  • Likes Given: 109
Then what?

Look for it.
What's next after that?

That remains to be worked out, but it's bound to be better than blindly plunging into reentry with a hole in your heatshield (edit: or anywhere else that would cause a loss of mission).
« Last Edit: 08/29/2016 07:32 pm by Hobbes-22 »

Online SWGlassPit

  • I break space hardware
  • Full Member
  • ****
  • Posts: 620
  • Liked: 522
  • Likes Given: 75
Who said the hole is in the heat shield?

Online yokem55

  • Full Member
  • ****
  • Posts: 579
  • Oregon (Ore-uh-gun dammit)
  • Liked: 350
  • Likes Given: 12
So in other words, compound conservatism. Sounds like a good recipe to increase overall costs.

NASA learned the hard way that just because a backup is in place, you cannot get away with a deficiency in a primary system.

In this case, the primary system is the vehicle's resilience to MMOD. The backup is inspections and operational precautions. Now I think it's perfectly reasonable to ask that the threat model not be over exaggerated and be backed up by solid data, but asking that the spacecraft handle the lion's share of the risk on their own is not unreasonable at all.

Online abaddon

  • Full Member
  • ****
  • Posts: 1804
  • Liked: 1320
  • Likes Given: 1298
It's not the same system.  It wasn't designed to be used to detect MMOD strikes, and -- surprise -- it didn't do a good job of doing so.  No human spacecraft has flown with an MMOD strike detection system.
It had accelerometers to sense impacts and it was capable of detecting MMOD strikes.  I didn't say it was good.  But it flew, and it existed.

Not sure what angle you're pushing from here, but I'm content to drop it at that.

Offline virnin

  • Full Member
  • *
  • Posts: 103
  • Kansas
  • Liked: 47
  • Likes Given: 42
ISS updates regularly report on Russian crew performing impact detection experiments.  One would hope we are all learning from their work?

Online A_M_Swallow

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 8692
  • South coast of England
  • Liked: 404
  • Likes Given: 184

If that even works (signal-to-noise ratio issues abound here), what would that accomplish?  You look at it and go, "yep, that's a strike."  Then what?

If pieced into the main room duck tape a patch across the hole to stop the air escaping. Pipes can be sealed with a plaster. Broken windows can be covered.

Damage to outside parts of the spacecraft may have to be repaired by a robot or EVA. Such a repair was performed to the ISS solar panels on January 30, 2007. There may be a way to glue or weld heat shield material across a hole the size of Columbia's.

Online guckyfan

  • Senior Member
  • *****
  • Posts: 6939
  • Germany
  • Liked: 1906
  • Likes Given: 1969

If that even works (signal-to-noise ratio issues abound here), what would that accomplish?  You look at it and go, "yep, that's a strike."  Then what?

If pieced into the main room duck tape a patch across the hole to stop the air escaping. Pipes can be sealed with a plaster. Broken windows can be covered.

Damage to outside parts of the spacecraft may have to be repaired by a robot or EVA. Such a repair was performed to the ISS solar panels on January 30, 2007. There may be a way to glue or weld heat shield material across a hole the size of Columbia's.

More likely IMO send a replacement vehicle up and use the damaged one only in the very unlikely case of a ISS evacuation. BTW if the pressure hull is compromised it is not only quite easy to fix but will inevitably be detected.

Offline srtreadgold

  • Engineer
  • Member
  • Posts: 37
  • Houston
  • Liked: 30
  • Likes Given: 102

If that even works (signal-to-noise ratio issues abound here), what would that accomplish?  You look at it and go, "yep, that's a strike."  Then what?

If pieced into the main room duck tape a patch across the hole to stop the air escaping. Pipes can be sealed with a plaster. Broken windows can be covered.

Damage to outside parts of the spacecraft may have to be repaired by a robot or EVA. Such a repair was performed to the ISS solar panels on January 30, 2007. There may be a way to glue or weld heat shield material across a hole the size of Columbia's.

Duct tape / plaster is not exactly what you want keeping reentry gasses/temperatures from breaching your delicate spacecraft.

Tags: