Author Topic: Biden administration potential and actual space policy  (Read 242505 times)

Offline yg1968

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Re: Biden administration potential and actual space policy
« Reply #1000 on: 11/23/2022 01:19 am »
I am not sure where this belongs but this is an interesting twitter thread on the history of the Asteroid Redirect Mission (ARM):

Quote from: Dr. Phil Metzger
1/n I was in some of the meetings when ARM was decided. We were told to visit an asteroid, but the out-and-back to a long-synodic small body (no gravity assist) would be too long so radiation would exceed allowable. We had to invent an alternative and yet "visit an asteroid."

2/n I heard some astronauts laughing on the telecon, "hey, if we want to visit an asteroid, we can rent a winnebago and go visit one on a road trip!" When we reviewed the timeline for the out-and-back mission they allotted several days at the asteroid. One crew member asked...

3/ ... what they would be doing for that many days. Someone else spoke up, "The first day you will collect rocks. The next five days you will play cards until you are allowed to come home." Lol. True story.

4/ Fortunately, there was a paper published in 2010 that argued that the definition of an asteroid should be changed from >10m diameter to >1m diameter. This was the key thing NASA needed to justify bringing back a boulder and saying it is an asteroid. No joke -- a single paper.

5/ So the plan changed to robotically bringing back the "asteroid" so we could visit it without too much radiation to the crew and check the box that we did as told. Nevertheless, I agree it would've been a great mission, despite the crazy way we got to it.

6/ Because of my work in regolith technology, I was invited onto the Option B formulation team to snag a boulder OFF an asteroid rather than finding one orbiting the Sun. The reason we considered an Option B was because...

7/...we were starting to realize three problems with the original "option A" concept. First, we did not know where any small asteroids actually are (they all get lost immediately after finding them) so it would take years to find one as it closely passes the Earth, then...

8/...more years before its long synodic period brought it close enough to the Earth again to rendezvous and snag it. Only long synodic period rocks were wanted since they offered low-enough delta-v to bring back. Second, we realized their rotational dynamics were a problem.

9/ Generally, a body will (1) rotate, (2) precess, and (3) nutate. To snag a multi-ton rock with a low-mass spacecraft, there's a moment of truth when the spacecraft jerks and is put into the same motion as the rock by brute force. No getting around that. Trying to align...

10/...with a precessing, nutating pole on the rock to minimize the jerk of the spacecraft would be very difficult, especially since it had to be automated as it will occur on the other side of the Sun from Earth during the minimum delta-v mission.

11/... Third, we were learning about that same time that most asteroids are rubble piles. Only the fast-spinners are likely not rubble piles. Rubble piles continually shed mass so that the Poynting-Robinson effect will not spin them up to high rotational rates. So a dilemma:

12/... (A) if you get a fast spinner, how to you grab it and ultra-jerk the flimsy spacecraft without ripping off the solar arrays, or (B) if you get one that isn't a fast spinner, then as soon as you touch it, it flies into a million small pieces because it's a rubble pile.

13/ ...These are literally the discussions that were occurring during that period. We were afraid that if we touched it, and it flew apart, and the spacecraft came back without an asteroid, it would be a deep embarrassment to the space agency. So someone had a bright idea...

14/ JAXA had just visited asteroid Itokawa, and we were all in awe over the many large boulders on the surface. Now Itokawa is a rubble pile, so that means the pieces had collected over time.

15/. That means those boulders USED to be separate asteroids before they merged onto the surface of Itokawa (ummm. well, also the new definition of an asteroid helped, since we couldn't very well snag a >10m diameter boulder off Itokawa.)

16/ So someone said, you know, if we try to grab one of those boulders off Itokawa and it crumbles, we have a WHOLE BUNCH MORE to choose from during the same mission. So Option B was to pull a boulder off a larger asteroid, declare "you are now a free asteroid" and bring it back.

17/ So it would be more complicated than going in a Winnebago to visit an asteroid that has already landed on Earth. By visiting one that landed on another asteroid we could turn it back into an asteroid in space and then visit it, then check the box given us by the politicians.

18/ But the goal of our formulation team was to find what high-quality science and technology goals could be met by this sort of mission, and we did find a lot of real, good science. Example: a planetary defense gravity tug test using the boulder mass we had just extracted.

19/ I still find this story to be hilarious, years later, which I guess is why I am typing a long reply thread about it. My point is, the politics were cra[z]y, but we would still get excellent science and tech from it. I think it would've been a great mission.

20/ One last point I neglected to say. Rumors within NASA say that it was Buzz Aldrin who put the idea of this mission into the ear of the president, who then told us to do it before finding out if it was doable. I think Buzz actually meant to visit Phobos, a Mars-captured rock.

21/21 The politicians thought, the Moon is too easy, Mars is still too hard, so let's go in-between. Unfortunately, the long synodic period by being closer than Mars coupled with no gravity or atmosphere to capture a spacecraft made it worse than either the Moon or Mars. Lol.

https://twitter.com/DrPhiltill/status/1595233546960048129
« Last Edit: 11/23/2022 01:30 am by yg1968 »

Offline Proponent

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Re: Biden administration potential and actual space policy
« Reply #1001 on: 11/23/2022 06:16 pm »
Thank you! That is the most interesting post I have read here in quite a while.

EDIT: "us" to "is"
« Last Edit: Today at 12:03 am by Proponent »

Offline yg1968

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« Last Edit: 12/01/2022 02:53 am by yg1968 »

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