Good. Hopefully it never comes unstuck
Asteroid samples escaping from jammed NASA spacecraft
31–40 of 72 posts
Re: Asteroid samples escaping from jammed NASA spacecraft
#32Earlier quoted context omitted.
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).
They might not even be able to measure that small of a difference in the spacecraft's acceleration, to be honest. We're talking about a difference in grams of a spacecraft that's somewhere north of 1000kg right now - wet mass was maybe 1529kg at launch [according to NASA; Lockheed said the bus could be up to 2000kg at launch, so I'm not sure who to believe being honest - it's a little hard to believe they'd risk things and short the mission on that much hydrazine], dry mass 860kg, split the difference and it's probably around 1200kg [or up to 1500kg] currently.
It's a little easier to believe they could detect whether or not they got 60g by the last significant digit change in the moment of inertia from their instruments by nulling out the rotation... It's a little harder to believe they could detect a difference between 0 and maybe 500g in the sample return container via their acceleration data. I doubt they even know how much hydrazine and helium is left with all that much precision - at more than hundred grams a second burned, it's easy to believe there's some amount of accounting slop.
Re: Asteroid samples escaping from jammed NASA spacecraft
#33Earlier 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.
Then again NASA has a $22B budget.
Many large corporations have budgets in excess of that and still struggle with delivering solutions and software updates. Internally or externally.
Re: Asteroid samples escaping from jammed NASA spacecraft
#34Earlier 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.
Instead of adjusting fuel you can probably compensate by changing when you do the burn. And there are likely to be midcourse corrections anyways.
That makes me wonder: how is it possible to even determine what the correction should be? Space is vast, how do they determine the position of a microscopic vessel precisely enough to know how much to burn?
Re: Asteroid samples escaping from jammed NASA spacecraft
#35Earlier quoted context omitted.
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..."
Usually its 99.7% percent of the time: three standard deviations.
Re: Asteroid samples escaping from jammed NASA spacecraft
#36As 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.
And now optical navigation has been flight proven so it can be used on other missions.
Re: Asteroid samples escaping from jammed NASA spacecraft
#37At the original 60oz/$800 million dollars, would that make it the most expensive bit of mineral on Earth in 2023?
Re: Asteroid samples escaping from jammed NASA spacecraft
#38Earlier quoted context omitted.
> "Lauretta said there is nothing flight controllers can do to clear the obstructions and prevent more bits of Bennu from escaping, other than to get the samples into their return capsule as soon as possible." This, I'm guessing. Also, I found these parts interesting: >"Regardless of what’s on board, Osiris-Rex will still leave the vicinity of the asteroid in March — that’s the earliest possible departure given the r…
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…
> But why can't they spin the spacecraft after the sample is secure in the return capsule, but before reaching Earth? Is it precisely in the center of mass?
They might be able to, but there’s no reason to. The purpose of the sample mass measurement was to determine if they needed to try again, however that’s not an option with a jammed container.
Re: Asteroid samples escaping from jammed NASA spacecraft
#39Imagine the pickup managed to deviate the asteroids course so that it hits us! You wanted 100 grammes of rock, 78 billion kg incoming! :D
Re: Asteroid samples escaping from jammed NASA spacecraft
#40Earlier quoted context omitted.
Instead of adjusting fuel you can probably compensate by changing when you do the burn. And there are likely to be midcourse corrections anyways.
That makes me wonder: how is it possible to even determine what the correction should be? Space is vast, how do they determine the position of a microscopic vessel precisely enough to know how much to burn?
The primary instrument is probably a star tracker. It's possible to position yourself within the galaxy to a very high degree of accuracy by looking at changes in relative position of stars and planets which have a known "position" (really orbits).