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‘Oumuamua, Thin Films and Lightsails

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Re: ‘Oumuamua, Thin Films and Lightsails

#51

Post by mulmen »

stephengillie wrote: post #40
d_burfoot wrote: post #39

Paging Elon Musk, Jeff Bezos, et al: the next time one of these objects appears, we should try to capture it somehow, or at least divert its trajectory enough that it stays in the solar system and we can study it further. Nabbing one of these things would be a spectacular achievement, comparable to the moon landings, and would likely be of significant scientific value.

Musk missed, and his car is headed for the asteroid belt instead of Mars.

Based on my understanding of the Falcon Heavy launch and objectives this is an unfair characterization. The plan was never to put the car in orbit around Mars or hit the planet directly. The plan was to prove that Falcon Heavy can move a payload with the weight of the car at least as far as Mars. Shooting it into the asteroid belt demonstrates the capability of the rocket.

Re: ‘Oumuamua, Thin Films and Lightsails

#53

Post by ansible »

abecedarius wrote: post #34
Tossrock wrote: post #18

Given Oumuamua's well documented non-gravitational acceleration, what was the cause? That's the key question this article – and the paper it cites – are investigating. Comet-like off-gassing has been mostly ruled out due to the lack of observed dust or gas around the object, as well as lack of effect on spin. The paper suggests that a highly reflective 0.3mm-thick film 20m in diameter could be consistent with the obs…

It’s a fascinating mystery, but I gotta say that’d make a crappy lightsail, considering that even at our current tech level we could make a much lighter one if we could manufacture it in space. (The experiments that have flown were all constrained to survive launch and unfolding.)

Yes.

Something of that size (area) and weight doesn't seem like some kind of naturally occurring object though.

Even if it is a piece of debris, that is super, super interesting.

Eh, who am I kidding, even if it was produced through some natural process, that is still interesting.

Re: ‘Oumuamua, Thin Films and Lightsails

#54

Post by mulmen »

d_burfoot wrote: post #39

Paging Elon Musk, Jeff Bezos, et al: the next time one of these objects appears, we should try to capture it somehow, or at least divert its trajectory enough that it stays in the solar system and we can study it further. Nabbing one of these things would be a spectacular achievement, comparable to the moon landings, and would likely be of significant scientific value.

Capturing this object would have required the effort of multiple Apollo prgrams in a timeframe that is shorter by orders of magnitude. It’s far beyond the capabilities of Musk, Bezos and anyone alive today. Pulling it off would make the Moon landing look like parallel parking.

Re: ‘Oumuamua, Thin Films and Lightsails

#55

Post by mannykannot »

Tossrock wrote: post #18

Given Oumuamua's well documented non-gravitational acceleration, what was the cause? That's the key question this article – and the paper it cites – are investigating. Comet-like off-gassing has been mostly ruled out due to the lack of observed dust or gas around the object, as well as lack of effect on spin. The paper suggests that a highly reflective 0.3mm-thick film 20m in diameter could be consistent with the obs…

Assuming a uniform thickness and density, is the acceleration of a light sail not independent of area? I get the impression that the radius given is an upper limit based on the apparent magnitude and assuming a high albedo.

The light curve indicates that the object is tumbling, so a thin sheet would rarely (if ever) be oriented approximately optimally to act as a sail. I have not figured out how the authors have taken this into account in their calculation - could it be as simple as halving the area to give an effective value?

Re: ‘Oumuamua, Thin Films and Lightsails

#56

Post by modzu »

gwern wrote: post #46
rossdavidh wrote: post #19

While I find it highly unlikely, it does raise an interesting point about Fermi's Paradox, which is that even if there were enough alien life out there for its discarded light sails to go hurtling through our solar system every once in a while, we might not get any more evidence of it than this article demonstrates. So, it's almost certainly not a light sail, but even if it were, we would never know.

Fermi's paradox demonstrates it's almost certainly not a light sail. For it to be a light sail which was observed by chance by our totally unprepared observatories after a window of less than a century but also consistent with all our observations of the universe, we would need to hypothesize that we got extraordinarily lucky to observe a super-rare artifact, or that countless (or one vast) interstellar, pan-galactic…

thats not true. if the probability of whether or not its a sail could be calculated, it would have been in the paper ;)

Re: ‘Oumuamua, Thin Films and Lightsails

#57

Post by coleifer »

jolesf wrote: post #35

"Oumuamua appears to have originated at the Local Standard of Rest (LSR), which is the galactic frame of reference." Is a very interesting side-note

Wikipedia says:

> In fact, the strong correlation between ʻOumuamua's velocity and the local standard of rest might mean that it has circulated the Milky Way several times and thus may have originated from an entirely different part of the galaxy.

Re: ‘Oumuamua, Thin Films and Lightsails

#58

Post by [deleted] »

mannykannot wrote: post #55
Tossrock wrote: post #18

Given Oumuamua's well documented non-gravitational acceleration, what was the cause? That's the key question this article – and the paper it cites – are investigating. Comet-like off-gassing has been mostly ruled out due to the lack of observed dust or gas around the object, as well as lack of effect on spin. The paper suggests that a highly reflective 0.3mm-thick film 20m in diameter could be consistent with the obs…

Assuming a uniform thickness and density, is the acceleration of a light sail not independent of area? I get the impression that the radius given is an upper limit based on the apparent magnitude and assuming a high albedo. The light curve indicates that the object is tumbling, so a thin sheet would rarely (if ever) be oriented approximately optimally to act as a sail. I have not figured out how the authors have take…

[deleted]

Re: ‘Oumuamua, Thin Films and Lightsails

#59

Post by [deleted] »

mulmen wrote: post #51
stephengillie wrote: post #40

Earlier quoted context omitted.

Musk missed, and his car is headed for the asteroid belt instead of Mars.

Based on my understanding of the Falcon Heavy launch and objectives this is an unfair characterization. The plan was never to put the car in orbit around Mars or hit the planet directly. The plan was to prove that Falcon Heavy can move a payload with the weight of the car at least as far as Mars. Shooting it into the asteroid belt demonstrates the capability of the rocket.

[deleted]

Re: ‘Oumuamua, Thin Films and Lightsails

#60

Post by xrayzerone »

stephengillie wrote: post #40
d_burfoot wrote: post #39

Paging Elon Musk, Jeff Bezos, et al: the next time one of these objects appears, we should try to capture it somehow, or at least divert its trajectory enough that it stays in the solar system and we can study it further. Nabbing one of these things would be a spectacular achievement, comparable to the moon landings, and would likely be of significant scientific value.

Musk missed, and his car is headed for the asteroid belt instead of Mars.

Your comment demonstrates absolute cluelessness with regards to the goals of the FH launch / second stage trajectory.
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