The Astronomy Thread
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I can't wait to see the year 2400 blooper reel of this technology where the engagement clamp release timing fails and the spacecraft get launched back into Earth's surface at 40k mph.
(Also, holy shit, the acceleration you'd experience as a passenger if you're talking going from airline cruise speed to interplanetary speeds in a short time.)
LachiusTZ
Rogue Deathwalker Box
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Did you do the math?
I bet its a viable tech. Prolly one of the easier ones.
A lot better than counter rotating magnetic rings to create an orbital ring. A lot less risky and easier.
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[Edit: I suck at numbers. Thanks for correction, Ukerric.]
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Ukerric
Bearded Ape
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Which equates to 6.2 km/s.
And that's where you made a "small" unit error. See above (you're calculating in km/h, not km/s). You need to accelerate to 6.2km/s plus 11.2km/s escape velocity (because you're losing said velocity as you move out of Earth's gravity well on your way to Mars) for 17.2km/s over 1/2pi x 1000km, which is a bit above the acceleration of a conventional rocket (around 9.5G).
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Void
BAU BAU
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That's not how centrifugal force is calculated. You don't just take the starting velocity and the ending velocity and toss a diameter on there. It depends on a ton of other factors, the biggest being how long it takes to get from the bottom of the arc to the top (or vice versa). We don't know all of the factors involved, so any calculations are just wild guesses really, but just doing a quick and dirty calculation with some sample numbers, you're already down to 4g if you take around 20 minutes to traverse the arc in a 10,000 kg ship. With a 1000 km tether, 20 minutes is pretty fucking fast, so drop that to an hour and you're well within acceptable limits. I think taking an hour to "hook" into position for your flight to Mars is way faster than anyone would expect, so I'm pretty sure we're good. It would probably be much longer than that to keep the "catch" window as large as possible.
Also, that 86,000 lbf is on the tether, not on the people.
It is possible I made a huge gaff while tossing these numbers in here, so let me know if I did, but I'm pretty sure we're still talking about exponentially less than 775g. Or even 77g.
(EDIT: I slightly misspoke. The 20 minutes is for a full rotation, which is what is used in the equation. Since you're only traversing half the arc, it would actually only be 10 minutes of travel time for you. The calculation should still be correct, you just don't have to sit through more than half of it to get to the release point. Unless I'm totally wrong somewhere else, which is completely possible.)
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Seconds, hours, what's the difference? Touche. This is why you don't crunch numbers live. Board needs "embarrassed correction" reaction. I still get 60 G's though.
Using m and s throughout: (6195^2 - 278^2) / (2 * (0.5 * 2* pi * 10,000)) ~= 610 m/s^2
They still have to be accelerated along the arc to the final tangential velocity over a distance of half the circumference. That's combined with centrifugal forces, which I admittedly ignored but would only make it worse.
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LachiusTZ
Rogue Deathwalker Box
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C
Captain Suave
Being wrong isn't embarrassing. Well, unless your talking mad shit. Lol. Refusing to at admit you are when everyone else knows you are, is.
Two things:
Something like this is more useful for moving gear, since every person is going to require X tons of gear and supplies. Sending gear and supplies, receiving raw materials etc
And Transit time was at a minimum 3 months, five months was the supposed expectation.
Being wrong isn't embarrassing. Well, unless your talking mad shit. Lol. Refusing to at admit you are when everyone else knows you are, is.
Two things:
Something like this is more useful for moving gear, since every person is going to require X tons of gear and supplies. Sending gear and supplies, receiving raw materials etc
And Transit time was at a minimum 3 months, five months was the supposed expectation.
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Tuco
I got Tuco'd!
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I'm a sucker for colorful and well designed cartoons, but I don't see a mechanical limitation to the tether as presented.
One big problem with it is that there isn't an equitable amount of mass leaving and entering Earth. We're usually sending shit up and letting it de-orbit. It's rare that we bring anything back in, I'd be surprised if the ratio between mass sent to orbit and mass sent from orbit is even 0.1%. Even in an asteroid mining future I bet there'd be more stuff coming up than coming down. So you'll have to spend a lot of effort propelling the skyhook. Maybe you can use some solar sail or something to keep her rolling, but I don't know how that'd work if it's in low earth orbit.
I'd love to hear what Musk has to say about it, since he's talking about 1,000 starship launches for all his bullshit. At what point does making a skyhook pay off?
www.businessinsider.com
One big problem with it is that there isn't an equitable amount of mass leaving and entering Earth. We're usually sending shit up and letting it de-orbit. It's rare that we bring anything back in, I'd be surprised if the ratio between mass sent to orbit and mass sent from orbit is even 0.1%. Even in an asteroid mining future I bet there'd be more stuff coming up than coming down. So you'll have to spend a lot of effort propelling the skyhook. Maybe you can use some solar sail or something to keep her rolling, but I don't know how that'd work if it's in low earth orbit.
I'd love to hear what Musk has to say about it, since he's talking about 1,000 starship launches for all his bullshit. At what point does making a skyhook pay off?
Elon Musk thinks it would take 1,000 rockets 20 years to set up a self-sustaining city on Mars
Musk claimed earlier this week that it would only cost $2 million to launch SpaceX's Starship rocket, designed to carry 100 passengers.
www.businessinsider.com
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LachiusTZ
Rogue Deathwalker Box
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Tuco
Advanced Electric Propulsion System passes full-power test milestone
Aerojet Rocketdyne and NASA's Advanced Electric Propulsion System (AEPS) thruster has passed a major milestone, completing its first full-power test. Designed to be used by NASA's Gateway lunar orbital outpost as well as manned and unmanned deep-space missions, the AEPS Hall thruster ran stably at…
newatlas.com
Once the economics breaks past the cost of mining or whatever musk thinks he will do on Mars.
Building the thing would cost a mountain
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Ukerric
Bearded Ape
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Well, of course, if you accelerate using a 10km ring instead of a 1000km one...
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Melvin
Blackwing Lair Raider
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I'm a sucker for colorful and well designed cartoons, but I don't see a mechanical limitation to the tether as presented.
One big problem with it is that there isn't an equitable amount of mass leaving and entering Earth. We're usually sending shit up and letting it de-orbit. It's rare that we bring anything back in, I'd be surprised if the ratio between mass sent to orbit and mass sent from orbit is even 0.1%. Even in an asteroid mining future I bet there'd be more stuff coming up than coming down. So you'll have to spend a lot of effort propelling the skyhook. Maybe you can use some solar sail or something to keep her rolling, but I don't know how that'd work if it's in low earth orbit.
I'd love to hear what Musk has to say about it, since he's talking about 1,000 starship launches for all his bullshit. At what point does making a skyhook pay off?
Elon Musk thinks it would take 1,000 rockets 20 years to set up a self-sustaining city on Mars
Musk claimed earlier this week that it would only cost $2 million to launch SpaceX's Starship rocket, designed to carry 100 passengers.
A couple things popped into my mind that will help lessen the impact of that problem.
The space trebuchet incentivizes materials being sent back. All of a sudden a massive shipment of ores or whatever has value as a source of energy for the space fidgit spinner system, in addition to its raw material value on the surface.
The spacecraft will presumably be similar to the space shuttles in that every single launch is done with the intention to return to the surface. I believe there's room for that type of ship to fill new niches alongside the more traditional niche that more historic rockets fill.
I'd also love to see the bottom line of Musk's analysis of the concept too. It looks good from my point of view though.
Tuco
I got Tuco'd!
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I'd be kind of curious to know what new demands there would be for rare earth metals if the supply dramatically spiked. Like, if Elon Musk started dropshipping asteroids rich in ruthenium, rhodium, palladium, osmium, iridium and platinum etc, would we start to be able to make arc reactors and shit? If so I can see a continual source of controlled mass entering the earth's atmosphere.
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Mudcrush Durtfeet
Hungry Ogre
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Those elements you listed are not rare earth elements. Actual rare earth elements on Earth are not particularly rare, but generally not found in concentrated deposits. We could mine them if it was profitable. If I recall correctly, some years ago there was stuff going on about getting the US gov to help finance American mines or somethng like that. It didn't happen. Probably cheaper to mine these on Earth than on asteroids, at least at this time.
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If we want asteroid mining to be feasible, we need cheaper access to space and cheaper interplanetary transport level craft (generally). SpaceX is the best hope to enable others to get into this. No one else seems to be seriously likely to develop the capability in the near future. ULA is all about the pork, not at all about the cheap access to space. Blue Origins has yet to actually demonstrate an orbital craft of any kind. Others (or these companies) might do this some day, but who knows.
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No to arc reactors and shit. Those are science fiction and are not currently based on reality in any way.
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Ppppffffft wake up to the new frontiers of science and Meta Materials!
The military doesn't invest heavily in it for shits and giggles.
Black projects broke the mold. They're always a few decades ahead of what's public.
Bring on the zero point tech!
Any day now...
Any day...
khorum
Murder Apologist
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Impractical for anywhere with an atmosphere but essential for anything without... like the moon or asteroids.
You could make a small scale one that's spun up with an ion thruster for sending whiffle balls of processed asteroid stuff back to cislunar lagrange points.
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