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Asteroid samples escaping from jammed NASA spacecraft

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Re: Asteroid samples escaping from jammed NASA spacecraft

#21

Post by londons_explore »

lolbot wrote: post #13
augusto-moura wrote: post #6

Earlier quoted context omitted.

> Blowing a raspberry in the surface of the asteroid Classic Manley

From TFV: "In order to be able to perform the landing they needed to update their software to give it optical navigation abilities ..." Imagine being part of the team that had to do that, fast, chop-chop, or else their billion dollar space mission would fail miserably. "Oh, you only need us to implement vision. Ok, no biggie."

I assume it was more a case of "We have an algorithm that successfully lands the craft 80% of the time, but we would like it to be 99% of the time, so get to working on it..."

Re: Asteroid samples escaping from jammed NASA spacecraft

#22

Post by shadowgovt »

moron4hire wrote: post #20
JshWright wrote: post #4

As with all "current events in space", Scott Manley has an excellent video on this. https://youtu.be/cmQfWuFbLNg

"So they actually performed a software upgrade of on the spacecraft to give it optical navigation capabilities..." God dammit. And here I have trouble getting software updates into a server I have full control over on Earth.

Sadly, most of us don't have the luxury of working in environment where (a) it's mandated that we set up a 1-for-1 test rig with the production infrastructure and (b) management will accept the answer "I need to test for all possible contingencies because failure is not an option."

(Most of us are writing code in an environment where failure is totally an option, as long as it's fast and restoration is quick ;) ).

Re: Asteroid samples escaping from jammed NASA spacecraft

#23

Post by shadowgovt »

SamBorick wrote: post #8
rhn_mk1 wrote: post #7

Earlier quoted context omitted.

Thanks. That means there are two containers: the open one where the samples are now, and the sealed return capsule, where the contents will be transferred soon. In that light, this quote confuses me: > scientists won’t know how much the sample capsule holds until it’s back on Earth. They wanted to spin the spacecraft to measure the mass, but they can't risk losing more samples from an open container. But why can't th…

I recommend the scott manly video another commenter linked to for a more full explanation, but: The sample container that's currently jammed open is on the end of a long arm, while the sample return capsule is mounted on the body of the spacecraft. The only way to measure mass in free-fall is to spin the entire craft and measure where the center of rotation is compered to before the sample capture. The difference is…

They should also be able to figure it out via delta-V per unit of thrust when they execute any orbit-change maneuvers to return to Earth, but that's a much less accurate metric (perhaps not accurate enough to differentiate a spare 100 grams of material).

Re: Asteroid samples escaping from jammed NASA spacecraft

#24

Post by moron4hire »

shadowgovt wrote: post #22
moron4hire wrote: post #20

Earlier quoted context omitted.

"So they actually performed a software upgrade of on the spacecraft to give it optical navigation capabilities..." God dammit. And here I have trouble getting software updates into a server I have full control over on Earth.

Sadly, most of us don't have the luxury of working in environment where (a) it's mandated that we set up a 1-for-1 test rig with the production infrastructure and (b) management will accept the answer "I need to test for all possible contingencies because failure is not an option." (Most of us are writing code in an environment where failure is totally an option, as long as it's fast and restoration is quick ;) ).

Another part of the difficulty with updating servers is that updates are rather opaque. My own software on any given server is maybe 0.1% of all the software running on it (if even that). The other 99.9% is someone else's code: the operating system, the software runtime, the libraries, etc. So one doesn't really have a lot of insight into what is about to happen to the server without running a duplicate setup, which as you point out is pretty difficult to get right. I'm sure NASA has much more visibility into all the software that is running on their spacecraft.

Re: Asteroid samples escaping from jammed NASA spacecraft

#25

Post by awalton »

Jaruzel wrote: post #16
yetihehe wrote: post #11

Earlier quoted context omitted.

Bright side - they have so much material, that weighting it is not really that much of a concern. They were hopeful to get maybe 50 grams of material, they got about 400g, but maybe 100g will be lost. They won't have exact number, but they will have more than expected anyway.

Won't the extra weight require a change in earth re-entry fuel calculation etc. ? Without knowing the exact change in weight, they are going to be firing in the dark, as it were.

It's not enough to make a difference either way around it. The sample return container could be filled to the brim with pure osmium or iridium and would make it through the atmosphere just fine.

The scientists are mostly worried because they want as much of the sample as they can possibly get, and they're a little worried about closing the sample container - if there's a rock that gets stuck somewhere, the container might not seal shut and then they've got a real bad problem they've gotta contend with.

It's 2020, they don't want to jinx it, just shut it up in the container and wait for the time capsule to arrive in 2023.

Re: Asteroid samples escaping from jammed NASA spacecraft

#26

Post by LeifCarrotson »

yetihehe wrote: post #17
Jaruzel wrote: post #16

Earlier quoted context omitted.

Won't the extra weight require a change in earth re-entry fuel calculation etc. ? Without knowing the exact change in weight, they are going to be firing in the dark, as it were.

I don't know that much, but I suppose they will do a burn and then some corrections. If mass difference is big enough to be detectable for reentry, it will be detectable when they are going back to earth.

A key difference is that spinning the full satellite with the arm extended and measuring the center of rotation measures the mass of the samples collected regardless of the thrusters/reaction wheels.

Measuring the trajectory of the reentry vehicle gives a parameter that can be used to estimate the sample mass assuming nominal thrust values, but you can't distinguish between an underperforming or overperforming rocket engine and heavier or lighter samples. This ambiguity doesn't really matter for the purposes of burn correction - you need to get to the correct reentry trajectory no matter what caused the deviation - but your sample mass estimate may be off.

I don't think there's a whole lot of utility in knowing the sample mass, as long as you've got enough (and they've definitely got enough!), it would just help satiate the curiosity of the scientists and engineers who otherwise have to wait a few more years to see their results.

Re: Asteroid samples escaping from jammed NASA spacecraft

#27

Post by dnautics »

Jaruzel wrote: post #16
yetihehe wrote: post #11

Earlier quoted context omitted.

Bright side - they have so much material, that weighting it is not really that much of a concern. They were hopeful to get maybe 50 grams of material, they got about 400g, but maybe 100g will be lost. They won't have exact number, but they will have more than expected anyway.

Won't the extra weight require a change in earth re-entry fuel calculation etc. ? Without knowing the exact change in weight, they are going to be firing in the dark, as it were.

Instead of adjusting fuel you can probably compensate by changing when you do the burn. And there are likely to be midcourse corrections anyways.

Re: Asteroid samples escaping from jammed NASA spacecraft

#28

Post by BurningFrog »

moron4hire wrote: post #20
JshWright wrote: post #4

As with all "current events in space", Scott Manley has an excellent video on this. https://youtu.be/cmQfWuFbLNg

"So they actually performed a software upgrade of on the spacecraft to give it optical navigation capabilities..." God dammit. And here I have trouble getting software updates into a server I have full control over on Earth.

Then again NASA has a $22B budget.

Re: Asteroid samples escaping from jammed NASA spacecraft

#29

Post by LeifCarrotson »

codeulike wrote: post #14

Not really 'jammed', I think they mean 'jam packed' edit: ok I see, it jammed because it was jam packed

I'm concerned that they'll have a hard time closing the reentry vehicle, that its hinge and hermetically sealing systems will become jammed open as well. There's no one available to wipe the gravel and dust off the sealing surface with their finger...

I'm not involved in the project, but I do work on terrestrial automation projects, often involving CNCs - chip management to prevent swarf accumulating on your hard stops and tapers is a real problem! Here, we have plenty of compressed air as well as gravity to clear chips, and preventative maintenance schedules for the stuff that the automated cleanup processes missed, and we remove parts to cleanrooms for important measurement stages, but that spacecraft is basically floating in a cloud of gravel...not a good environment for precision seals!

Re: Asteroid samples escaping from jammed NASA spacecraft

#30

Post by NortySpock »

bo0tzz wrote: post #10
7373737373 wrote: post #9

Is a second touchdown possible?

No, the spacecraft is already on a trajectory away from the asteroid, and any further maneuvering is not an option until the sample capsule has been stowed to avoid more debris spilling.

Disagree. The sample arm was designed with spare gas for up to 3 sampling attempts, so they could go back and get more if they didn't have enough.

Since their sample-cup is filled to the brim and spilling over on the first attempt, they are choosing to stow the sample container, rather than go for another (redundant) attempt with an already-full sample container.

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