Earth Return & Sample Science |
Earth Return & Sample Science |
Oct 24 2020, 07:02 AM
Post
#1
|
|
Merciless Robot Group: Admin Posts: 8785 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.
|
|
|
Oct 24 2020, 08:37 AM
Post
#2
|
|
Member Group: Members Posts: 404 Joined: 5-January 10 Member No.: 5161 |
|
|
|
Oct 24 2020, 01:30 PM
Post
#3
|
|
Newbie Group: Members Posts: 7 Joined: 26-December 06 Member No.: 1519 |
The audio of the 10/23/2020 teleconference can be accessed for 30 days at:
1-866-373-4996 |
|
|
Oct 24 2020, 06:55 PM
Post
#4
|
|
Member Group: Members Posts: 447 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. |
|
|
Oct 24 2020, 07:24 PM
Post
#5
|
|
Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
Looking at the apparent fragility of those "rocks" I wonder what is going to happen during the high g forces during entry. None of it will vanish, but it might lose some of the original structure.
|
|
|
Oct 24 2020, 09:18 PM
Post
#6
|
|
Member Group: Members Posts: 401 Joined: 5-January 07 From: Manchester England Member No.: 1563 |
It's a nice problem to have in a way... but it's still a problem . Still it sounds like the team have it in hand.
-------------------- |
|
|
Oct 24 2020, 09:56 PM
Post
#7
|
|
Senior Member Group: Members Posts: 2106 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. |
|
|
Oct 24 2020, 10:42 PM
Post
#8
|
|
Member Group: Members Posts: 127 Joined: 20-April 05 Member No.: 291 |
So they cancelled the spin because visual inspection confirmed an abundance of material?
|
|
|
Oct 25 2020, 12:33 AM
Post
#9
|
|
Member Group: Members Posts: 437 Joined: 14-December 15 Member No.: 7860 |
So they cancelled the spin because visual inspection confirmed an abundance of material? "...To preserve the remaining material..." "...Any movement to the spacecraft and the TAGSAM instrument may lead to further sample loss..." "...The loss of mass is of concern to me, so I’m strongly encouraging the team to stow this precious sample as quickly as possible - said Dante Lauretta..." ["some of sample particles appeared to be escaping slowly from the TAGSAM head - passing through small gaps where a mylar flap is slightly wedged open by larger rocks"] (here) I think that with very gentle and careful moving the TAGSAM head while enclosing it in the return capsule, and doing it without undue delay, the final loss of the collected mass (they collected about 400 g - much more than planned 60 g) will be insignificant. We have to keep our fingers crossed for this |
|
|
Oct 25 2020, 06:32 AM
Post
#10
|
|
Junior Member Group: Members Posts: 87 Joined: 17-May 08 Member No.: 4114 |
The audio of the 10/23/2020 teleconference can be accessed for 30 days at: FWIW, also on youtube (starts at ~13 minutes) https://www.youtube.com/watch?v=n274YX4xk_0 - just audio except for showing the gif from the press release for a while |
|
|
Oct 25 2020, 10:16 PM
Post
#11
|
|
Member Group: Members Posts: 613 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.... |
|
|
Oct 25 2020, 11:21 PM
Post
#12
|
|
Senior Member Group: Members Posts: 2542 Joined: 13-September 05 Member No.: 497 |
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. Agreed, I don't think thruster firing is going to tell you anything. But the other small forces on the spacecraft (e.g., radiation pressure) might be well enough characterized. Time will tell. The story is of course https://en.wikipedia.org/wiki/The_Cold_Equations -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
|
|
|
Oct 26 2020, 03:58 AM
Post
#13
|
|
Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
Apollo 13 had a bit of a concern regarding sample mass, but it was an issue of many kg, not g:
http://www.collectspace.com/news/news-0416..._souvenirs.html |
|
|
Oct 26 2020, 01:50 PM
Post
#14
|
|
Senior Member Group: Members Posts: 1592 Joined: 14-October 05 From: Vermont Member No.: 530 |
QUOTE (mcaplinger post Oct 23 2020 @ 06:56 PM Post #210) One thing that surprised me was Dante talking about "dust loading" (I think he said) on Navcam and SamCam. I wonder how dirty the nadir panel of the spacecraft is now? Any word on this? I wonder in the context of an extended mission (proposal? idea?). |
|
|
Oct 26 2020, 05:39 PM
Post
#15
|
|
Member Group: Members Posts: 306 Joined: 4-October 14 Member No.: 7273 |
If Bennu regolith is anywhere near as sticky as lunar regolith, that whole part of the spacecraft is probably filthy from the compressed nitrogen burst.
|
|
|
Lo-Fi Version | Time is now: 26th September 2024 - 08:32 AM |
RULES AND GUIDELINES Please read the Forum Rules and Guidelines before posting. IMAGE COPYRIGHT |
OPINIONS AND MODERATION Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators. |
SUPPORT THE FORUM Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member. |