24 ms·

If the container is open, how are they planning to retrieve the sample without losing it on reentry?

JshWright 6y ago
The container will be loaded inside a sealed reentry capsule.
jimmydorry 6y ago
> "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 relative locations of Earth and Bennu. The samples won’t make it back until 2023, seven years after the spacecraft rocketed away from Cape Canaveral." >Because of the sudden turn of events, scientists won’t know how much the sample capsule holds until it’s back on Earth. They initially planned to spin the spacecraft to measure the contents, but that maneuver was canceled since it could spill even more debris. >“I think we’re going to have to wait until we get home to know precisely how much we have,” Lauretta told reporters. “As you can imagine, that’s hard. ... But the good news is we see a lot of material.”
- rhn_mk1 6y ago
  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 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?
  - SamBorick 6y ago
    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 then used to calculate the sample mass. With the sample at the end of a long arm, the spacecraft doesn't have to rotate very fast to get a large enough difference in rotation to measure the sample. If the sample is in the return capsule, the moment is so much smaller that it's probably below the sensitivity of the instruments they were planning to use.
    - yetihehe 6y ago
      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.
      - Jaruzel 6y ago
        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.
        yetihehe 6y ago
        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.
        LeifCarrotson 6y ago
        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.
rtkwe 6y ago
There's a sample return vehicle that detaches with the sample canister inside of it. There's some concern with so much material floating around from the sample head no sealing properly that some bits might get in the way though. Scott Manley has a pretty good video about it as per usual when there's slightly vague space news. I've linked directly to where he's talking about the sample return portion of the mission. https://youtu.be/cmQfWuFbLNg?t=443 https://youtu.be/cmQfWuFbLNg?t=443

The container will be loaded inside a sealed reentry capsule.

> "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 relative locations of Earth and Bennu. The samples won’t make it back until 2023, seven years after the spacecraft rocketed away from Cape Canaveral." >Because of the sudden turn of events, scientists won’t know how much the sample capsule holds until it’s back on Earth. They initially planned to spin the spacecraft to measure the contents, but that maneuver was canceled since it could spill even more debris. >“I think we’re going to have to wait until we get home to know precisely how much we have,” Lauretta told reporters. “As you can imagine, that’s hard. ... But the good news is we see a lot of material.”

rhn_mk1 6y ago
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 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?
- SamBorick 6y ago
  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 then used to calculate the sample mass. With the sample at the end of a long arm, the spacecraft doesn't have to rotate very fast to get a large enough difference in rotation to measure the sample. If the sample is in the return capsule, the moment is so much smaller that it's probably below the sensitivity of the instruments they were planning to use.
  - yetihehe 6y ago
    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.
    - Jaruzel 6y ago
      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.
      - yetihehe 6y ago
        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.
        LeifCarrotson 6y ago
        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.

rtkwe 6y ago

There's a sample return vehicle that detaches with the sample canister inside of it. There's some concern with so much material floating around from the sample head no sealing properly that some bits might get in the way though. Scott Manley has a pretty good video about it as per usual when there's slightly vague space news. I've linked directly to where he's talking about the sample return portion of the mission. https://youtu.be/cmQfWuFbLNg?t=443 https://youtu.be/cmQfWuFbLNg?t=443