7 ms·

NASA Mars Mission Faces Setback After Heat Shield Cracks Under Pressure

76 points by yeukhon 8y ago

geuis 8y ago
Space is hard. Goes to show they have thorough and extensive testing and caught this now rather than losing the mission in 2020.
- mattnewton 8y ago
  Definitely this. Better to lose a shield prototype than a fancy rover you already spent millions to hurl into space.
  - mattashii 8y ago
    The article isn't 100% clear on this, but to me it reads that the actual heat shield that they were going to use in the mission broke (not a prototype). Which is still much better than the alternative (losing a multi-billion dollar project in Rapid Unscheduled Disassembly)
    - duskwuff 8y ago
      Yep. Much better for the heat shield to break in a test chamber on Earth and have to be rebuilt, than for it to break during Mars atmospheric reentry and end the mission.
- AnimalMuppet 8y ago
  Space is hard. Things get broke. Your mission still Must not choke. Burma Shave (H/T to the RhymeZone rhyming dictionary...)
JarlUlvi 8y ago
This is actually success - testing proved that a widget wasn't ready to be space qualified for a challenging mission. It broke in testing, enabling engineers to know about that they need a better design. Now, they're paying for a new shield, and all the engineering work that goes into that, rather than preparing the funeral for some astronauts and all the horribleness that goes into the loss of team members.
- ISL 8y ago
  Agreed, with the caveat that the loss would be a rover (and the resources, humanity, and time poured into the effort), not any human passengers. Testing did its job, and the shield did not!
toss1 8y ago
...Aaand, that's why we run the tests! Better to fix it in a component/unit test than to lose the entire project A successful test, identifying an flawed component design.
- mejari 8y ago
  >A successful test, identifying an flawed component design. It could also be a flawed component. Just because the test failed doesn't mean the design is flawed.
  - toss1 8y ago
    true, thx (definitely a flawed writing component there)
- TomK32 8y ago
  Every inch of this is true, good tests are our success meter. /s
- mattnewport 8y ago
  It's also worth pointing out that if your tests don't fail occasionally you may be over-engineering or being too cautious in your design and planning.
  - Sharlin 8y ago
    ...or your test coverage is insufficient.
- imglorp 8y ago
  Also, a learning opportunity. If it had just worked, we would know less. Sometimes you have to blow up a few things to make progress--ask Elon.
kodablah 8y ago
> Engineers at NASA's Jet Propulsion Laboratory are working with Lockheed Martin, the contractor that built the heat shield, to figure out why the shield cracked. [...] A NASA spokesman says the agency doesn't have an estimate of how much it will cost to replace the Mars mission's heat shield. Though I know it's often a counterproductive pursuit, I am curious where blame lies here. Did Lockheed build to NASA specs? I assume so, but say that it was determined that a manufacturing misstep that Lockheed made. Does the contract for a piece of equipment like this include indemnification for Lockheed, the opposite (that is must pass the tests to get paid), or is there no explicit accountability? I know sometimes things happen, I'm more curious about the money trail and preventative measures like any postmortem.
- jpollock 8y ago
  Blame doesn't matter. All that matters for money is "who accepted the risk". In a lot of contracts, the buyer lists the tests the object needs to pass prior to acceptance. Then there will be a chunk of money attached to passing that. If it fails, then they don't get paid (that chunk). After that, there may be more negotiation into who pays for the rework, but that's also typically in the contract. Usually the acceptance payment can be a large fraction of the total contract (30-50%). The same thing is done in just about every contract with a vendor. Even house renovations. I typically leave 30% riding on the final inspection passing.
  - cbanek 8y ago
    Money is one factor, but so is time. A lot of these kinds of parts like heat shields and expensive instruments are effectively one-offs, where there may be 1, 2 or 3 of them made, and usually the test articles aren't fit for flight because they determine defects that are later fixed in the one that flies. There are certain launch windows for Mars where Earth and Mars are closer together [1] that you really need to be ready for. If you miss it, you might have to wait 2 more years for the next window. Sometimes you can't get the necessary refit time no matter how much money you spend. [1] https://en.wikipedia.org/wiki/Exploration_of_Mars#Launch_windows https://en.wikipedia.org/wiki/Exploration_of_Mars#Launch_win...
  - 8y ago
aphextron 8y ago
In theory, shouldn't we be able to deflect the plasma generated during reentry with an EM field? I get that active generation would have all sorts of complexity/power/weight costs. But could it be possible to engineer some type of material which can passively convert thermal energy to a powerful enough EM field that would envelop the spacecraft and work as a "deflector dish"? I just feel like there has to be a better solution to reentry than ablation. It's the main thing that sticks out in my mind which kills true reusability.
- jschwartzi 8y ago
  It has to become plasma before it's susceptible to EM deflection. So you'd still have to heat it to 4000 degrees through friction. And so you'd still need a heat shield.
- Sharlin 8y ago
  If I understand correctly the main energy transfer mechanism to the heat shield is thermal radiation, not conduction or kinetic effects. The plasma is separated from the vehicle by a boundary layer. So it doesn’t help that the really hot stuff isn’t directly touching the heat shield.
  - aphextron 8y ago
    That definitely makes sense. I was thinking in terms of conduction, not radiation.
- gene-h 8y ago
  Absolutely, and NASA is currently investigating this. There is the idea of magnetoshell aerocapture[0][1], which is to create a shell of magnetized plasma around the spacecraft which can be used to slow down the atmosphere. There are a couple reasons why this is attractive. For one, you can modulate the size of the magnetized plasma shell and how much drag you make. Aerocapture, that is getting into orbit via dissipating momentum with planetary atmosphere, is a very risky maneuver because things like solar flares can change the height of the atmosphere causing there to be too much(crashing into the planet) or too little drag(flying off into space). Being able to change the size of the shell fixes this problem. The other is that this scales better than traditional aerocapture methods. The authors show in [0] how this could enable 2 tons of asteroid to be delivered to earth orbit, faster delivery of payloads to Mars orbit, and more economical delivery of payloads to orbit around outer planets like Neptune. There's a lot of promise for this technology and it's currently being developed for a cubesat demonstration mission[2]. This does not harvest any energy though, however, a separate NASA project did investigate the feasibility of generating power and capturing Mars' CO2 atmosphere to make O2 oxidizer through aerocapture[3] [0]https://iepc2017.org/sites/default/files/speaker-papers/iepc_youngvisionary_shimazukelly_iepc_2017_600.pdf https://iepc2017.org/sites/default/files/speaker-papers/iepc... [1]https://www.nasa.gov/sites/default/files/files/Kirtley_2012_PhI_PlasmaAerocapture.pdf https://www.nasa.gov/sites/default/files/files/Kirtley_2012_... [2]https://www.geekwire.com/2017/uw-team-wins-nasas-nod-small-satellites-magnetic-braking-systems/ https://www.geekwire.com/2017/uw-team-wins-nasas-nod-small-s... [3]https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170002795.pdf https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/201700...
billforsternz 8y ago
This is one of the reasons engineering is a difficult field, not just edge of the envelope engineering like this but routine product development. Sometimes it amazes me that anything ever gets shipped. Think about airliners. After billions of dollars of development, you have to pass critical safety tests (eg evacuation time tests). What happens if you fail the test in such a way that you can't fix it without more-or-less starting from scratch? How can anyone sign off on the development schedule? Yet they do and somehow or other eventually products tend to get shipped. Back in the day when I was a working engineer (embedded systems, telecom systems) I decided there was basically an unspoken conspiracy of silence. The pointy heads would demand a schedule. The engineering staff would provide it. There would be a generous allocation for all kinds of testing. But sometimes the results of testing would require new board layouts or other things that were basically catastrophic for the schedule (I'm thinking things like electromagnetic compatibility testing - stuff that wasn't in my wheelhouse thank god). The schedules would never factor in serious go-arounds like this yet it could and did happen and was one reason schedules were rarely met. To me the unspoken conspiracy was that we know we can't really control the development trajectory, but we'll sign off on it anyway. Because what else are you going to do? Apologising later is more practical than seeking permission for an open-ended schedule.
- cyberferret 8y ago
  Well, with respect to your airline scenario - most companies would design along with those industry specifications in mind from the outset. Even without doing so, considerable reverse engineering can still be achieved. The case of the De Havilland Comet comes to mind - they had to basically redesign the entire fuselage construction from the ground up once they realised the single layer pressure cell was a major design flaw.
  - billforsternz 8y ago
    I think the De Havilland Comet is actually a poster child for exactly how badly things can turn out rather than a good counter-example. The original mistake was apparently quite small - square windows instead of round. By the time they finally fixed this and shipped a solid and reliable product it was too late. Hundreds of people had died, Boeing and Douglas had entered the market with better planes and ate their lunch. The company died as well. You could make a case with only a little exaggeration that this mistake killed the British aerospace industry and setup the US for decades of dominance advanced technology industries.
smaili 8y ago
> The Mars 2020 mission's heat shield was undergoing stress-testing when it developed a crack that appeared around its entire circumference. The shield is designed to protect the rover as it enters the Martian atmosphere. "The test was designed to subject the heat shield to forces up to 20 percent greater than those expected during entry into the Martian atmosphere," NASA said in a statement. Gives a whole new meaning to the term "stress testing" :)
- maxander 8y ago
  Hate to be that guy, but I’d imagine this is closer to the original meaning if the term. Mechanical parts required to perform under pressure are much older than servers. :)
exabrial 8y ago
Maybe they forgot to convert inches into centimeters...
pfdietz 8y ago
The heat shield did not crack, the structure on which the heat shield would be mounted cracked. The PICA tiles had not been installed yet.

76 points by yeukhon 8y ago

Space is hard. Goes to show they have thorough and extensive testing and caught this now rather than losing the mission in 2020.

mattnewton 8y ago
Definitely this. Better to lose a shield prototype than a fancy rover you already spent millions to hurl into space.
- mattashii 8y ago
  The article isn't 100% clear on this, but to me it reads that the actual heat shield that they were going to use in the mission broke (not a prototype). Which is still much better than the alternative (losing a multi-billion dollar project in Rapid Unscheduled Disassembly)
  - duskwuff 8y ago
    Yep. Much better for the heat shield to break in a test chamber on Earth and have to be rebuilt, than for it to break during Mars atmospheric reentry and end the mission.
AnimalMuppet 8y ago
Space is hard. Things get broke. Your mission still Must not choke. Burma Shave (H/T to the RhymeZone rhyming dictionary...)

JarlUlvi 8y ago

This is actually success - testing proved that a widget wasn't ready to be space qualified for a challenging mission. It broke in testing, enabling engineers to know about that they need a better design. Now, they're paying for a new shield, and all the engineering work that goes into that, rather than preparing the funeral for some astronauts and all the horribleness that goes into the loss of team members.

ISL 8y ago
Agreed, with the caveat that the loss would be a rover (and the resources, humanity, and time poured into the effort), not any human passengers. Testing did its job, and the shield did not!

toss1 8y ago

...Aaand, that's why we run the tests! Better to fix it in a component/unit test than to lose the entire project A successful test, identifying an flawed component design.

mejari 8y ago
>A successful test, identifying an flawed component design. It could also be a flawed component. Just because the test failed doesn't mean the design is flawed.
- toss1 8y ago
  true, thx (definitely a flawed writing component there)
TomK32 8y ago
Every inch of this is true, good tests are our success meter. /s
mattnewport 8y ago
It's also worth pointing out that if your tests don't fail occasionally you may be over-engineering or being too cautious in your design and planning.
- Sharlin 8y ago
  ...or your test coverage is insufficient.
imglorp 8y ago
Also, a learning opportunity. If it had just worked, we would know less. Sometimes you have to blow up a few things to make progress--ask Elon.

kodablah 8y ago

> Engineers at NASA's Jet Propulsion Laboratory are working with Lockheed Martin, the contractor that built the heat shield, to figure out why the shield cracked. [...] A NASA spokesman says the agency doesn't have an estimate of how much it will cost to replace the Mars mission's heat shield. Though I know it's often a counterproductive pursuit, I am curious where blame lies here. Did Lockheed build to NASA specs? I assume so, but say that it was determined that a manufacturing misstep that Lockheed made. Does the contract for a piece of equipment like this include indemnification for Lockheed, the opposite (that is must pass the tests to get paid), or is there no explicit accountability? I know sometimes things happen, I'm more curious about the money trail and preventative measures like any postmortem.

jpollock 8y ago
Blame doesn't matter. All that matters for money is "who accepted the risk". In a lot of contracts, the buyer lists the tests the object needs to pass prior to acceptance. Then there will be a chunk of money attached to passing that. If it fails, then they don't get paid (that chunk). After that, there may be more negotiation into who pays for the rework, but that's also typically in the contract. Usually the acceptance payment can be a large fraction of the total contract (30-50%). The same thing is done in just about every contract with a vendor. Even house renovations. I typically leave 30% riding on the final inspection passing.
- cbanek 8y ago
  Money is one factor, but so is time. A lot of these kinds of parts like heat shields and expensive instruments are effectively one-offs, where there may be 1, 2 or 3 of them made, and usually the test articles aren't fit for flight because they determine defects that are later fixed in the one that flies. There are certain launch windows for Mars where Earth and Mars are closer together [1] that you really need to be ready for. If you miss it, you might have to wait 2 more years for the next window. Sometimes you can't get the necessary refit time no matter how much money you spend. [1] https://en.wikipedia.org/wiki/Exploration_of_Mars#Launch_windows https://en.wikipedia.org/wiki/Exploration_of_Mars#Launch_win...
- 8y ago

aphextron 8y ago

In theory, shouldn't we be able to deflect the plasma generated during reentry with an EM field? I get that active generation would have all sorts of complexity/power/weight costs. But could it be possible to engineer some type of material which can passively convert thermal energy to a powerful enough EM field that would envelop the spacecraft and work as a "deflector dish"? I just feel like there has to be a better solution to reentry than ablation. It's the main thing that sticks out in my mind which kills true reusability.

jschwartzi 8y ago
It has to become plasma before it's susceptible to EM deflection. So you'd still have to heat it to 4000 degrees through friction. And so you'd still need a heat shield.
Sharlin 8y ago
If I understand correctly the main energy transfer mechanism to the heat shield is thermal radiation, not conduction or kinetic effects. The plasma is separated from the vehicle by a boundary layer. So it doesn’t help that the really hot stuff isn’t directly touching the heat shield.
- aphextron 8y ago
  That definitely makes sense. I was thinking in terms of conduction, not radiation.
gene-h 8y ago
Absolutely, and NASA is currently investigating this. There is the idea of magnetoshell aerocapture[0][1], which is to create a shell of magnetized plasma around the spacecraft which can be used to slow down the atmosphere. There are a couple reasons why this is attractive. For one, you can modulate the size of the magnetized plasma shell and how much drag you make. Aerocapture, that is getting into orbit via dissipating momentum with planetary atmosphere, is a very risky maneuver because things like solar flares can change the height of the atmosphere causing there to be too much(crashing into the planet) or too little drag(flying off into space). Being able to change the size of the shell fixes this problem. The other is that this scales better than traditional aerocapture methods. The authors show in [0] how this could enable 2 tons of asteroid to be delivered to earth orbit, faster delivery of payloads to Mars orbit, and more economical delivery of payloads to orbit around outer planets like Neptune. There's a lot of promise for this technology and it's currently being developed for a cubesat demonstration mission[2]. This does not harvest any energy though, however, a separate NASA project did investigate the feasibility of generating power and capturing Mars' CO2 atmosphere to make O2 oxidizer through aerocapture[3] [0]https://iepc2017.org/sites/default/files/speaker-papers/iepc_youngvisionary_shimazukelly_iepc_2017_600.pdf https://iepc2017.org/sites/default/files/speaker-papers/iepc... [1]https://www.nasa.gov/sites/default/files/files/Kirtley_2012_PhI_PlasmaAerocapture.pdf https://www.nasa.gov/sites/default/files/files/Kirtley_2012_... [2]https://www.geekwire.com/2017/uw-team-wins-nasas-nod-small-satellites-magnetic-braking-systems/ https://www.geekwire.com/2017/uw-team-wins-nasas-nod-small-s... [3]https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170002795.pdf https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/201700...

billforsternz 8y ago

This is one of the reasons engineering is a difficult field, not just edge of the envelope engineering like this but routine product development. Sometimes it amazes me that anything ever gets shipped. Think about airliners. After billions of dollars of development, you have to pass critical safety tests (eg evacuation time tests). What happens if you fail the test in such a way that you can't fix it without more-or-less starting from scratch? How can anyone sign off on the development schedule? Yet they do and somehow or other eventually products tend to get shipped. Back in the day when I was a working engineer (embedded systems, telecom systems) I decided there was basically an unspoken conspiracy of silence. The pointy heads would demand a schedule. The engineering staff would provide it. There would be a generous allocation for all kinds of testing. But sometimes the results of testing would require new board layouts or other things that were basically catastrophic for the schedule (I'm thinking things like electromagnetic compatibility testing - stuff that wasn't in my wheelhouse thank god). The schedules would never factor in serious go-arounds like this yet it could and did happen and was one reason schedules were rarely met. To me the unspoken conspiracy was that we know we can't really control the development trajectory, but we'll sign off on it anyway. Because what else are you going to do? Apologising later is more practical than seeking permission for an open-ended schedule.

cyberferret 8y ago
Well, with respect to your airline scenario - most companies would design along with those industry specifications in mind from the outset. Even without doing so, considerable reverse engineering can still be achieved. The case of the De Havilland Comet comes to mind - they had to basically redesign the entire fuselage construction from the ground up once they realised the single layer pressure cell was a major design flaw.
- billforsternz 8y ago
  I think the De Havilland Comet is actually a poster child for exactly how badly things can turn out rather than a good counter-example. The original mistake was apparently quite small - square windows instead of round. By the time they finally fixed this and shipped a solid and reliable product it was too late. Hundreds of people had died, Boeing and Douglas had entered the market with better planes and ate their lunch. The company died as well. You could make a case with only a little exaggeration that this mistake killed the British aerospace industry and setup the US for decades of dominance advanced technology industries.

smaili 8y ago

> The Mars 2020 mission's heat shield was undergoing stress-testing when it developed a crack that appeared around its entire circumference. The shield is designed to protect the rover as it enters the Martian atmosphere. "The test was designed to subject the heat shield to forces up to 20 percent greater than those expected during entry into the Martian atmosphere," NASA said in a statement. Gives a whole new meaning to the term "stress testing" :)

maxander 8y ago
Hate to be that guy, but I’d imagine this is closer to the original meaning if the term. Mechanical parts required to perform under pressure are much older than servers. :)

exabrial 8y ago

Maybe they forgot to convert inches into centimeters...

pfdietz 8y ago

The heat shield did not crack, the structure on which the heat shield would be mounted cracked. The PICA tiles had not been installed yet.