Earth Return & Sample Science |
Earth Return & Sample Science |
Oct 24 2020, 07:02 AM
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#1
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Now that the 'boop' has been completed (with spectacular success!), we'll move the discussion to here for subsequent mission events.
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Oct 24 2020, 06:55 PM
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#2
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Member Group: Members Posts: 444 Joined: 1-July 05 From: New York City Member No.: 424 |
Thanks to for that link.
It was a great press conference. Even though Brian's helpful summary covered most of the the major points, it made fascinating listening, with detailed, clear, and fluent presentations and answers from Dante Lauretta and Thomas Zurbuchen, and sharp, business-like questions from well-informed reporters. The stow operation is currently expected to begin on Tuesday. As Brian mentioned, the mission is seeking substantial extra DSN coverage in order to do something unusual for robotic spacecraft: conduct an operation interactively with "the ground in the loop." The revised stow plan will have a number of check points, at which the operation will pause while images are downloaded and analyzed to determine whether to proceed with the plan or try something different. As a result the stow operation is expected to last three days, instead of several hours as originally planned. The previously scheduled activity of spinning the spacecraft with the arm extended to obtain a moment of inertia measurement has been cancelled, and Lauretta pretty much ruled out any other possibility for measuring the sample mass (as opposed to estimating the mass from images) prior to landing. However, he did seem to acknowledge that there had not been any occasion to think about a different way such a measurement could be taken during the return trip. I suppose it's possible they might come up with a way to tease some sample mass information out of trajectory telemetry during the return voyage. |
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Oct 24 2020, 09:56 PM
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#3
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Senior Member Group: Members Posts: 2082 Joined: 13-February 10 From: Ontario Member No.: 5221 |
However, he did seem to acknowledge that there had not been any occasion to think about a different way such a measurement could be taken during the return trip. I suppose it's possible they might come up with a way to tease some sample mass information out of trajectory telemetry during the return voyage. Assuming the mass without the sample (including fuel and subtracting the nitrogen gas used) is known precisely enough, there should be a slight difference in how it 'handles' during maneuvers like the Earth return burn and any TCMs. |
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Oct 25 2020, 10:16 PM
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#4
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Member Group: Members Posts: 610 Joined: 23-February 07 From: Occasionally in Columbia, MD Member No.: 1764 |
Assuming the mass without the sample (including fuel and subtracting the nitrogen gas used) is known precisely enough, there should be a slight difference in how it 'handles' during maneuvers like the Earth return burn and any TCMs. In theory, yes (I think I remember reading a scifi story where a stowaway on a spacecraft is discovered this way). But in practice, this is a very small signal to look for (if you want to measure a 400g sample to 10%, as part of a 400kg spacecraft, that's a 0.01% precision) I think thruster performance is probably not more consistent than 1%, maybe worse. Measuring spin rates, and changes therein is something that can be done with exquisite precision, but more particularly putting the sample mass out on the TAGSAM arm gives a large moment arm, so the sample mass 'signal' component of the vehicle's moment of inertia. So having a viable retrieval of sample mass from this spin exercise does not mean you can do it with useful precision in a translation manoeuvre.... |
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Oct 27 2020, 12:23 AM
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#5
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Member Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 |
In theory, yes (I think I remember reading a scifi story where a stowaway on a spacecraft is discovered this way). "The Cold Equations" https://docs.google.com/viewer?a=v&pid=...MmU1OTQ2YWViOWY |
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