The Astronomy Thread

Mudcrush Durtfeet

Mudcrush Durtfeet

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MusicForFish said:
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...
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They were the reason we kept trying for higher atomic number man-made elements. My thought is that they wanted to use elements in the island of stability to make better bombs.

Doesn't work though, because A) we currently don't have a way to get to the island and B) there are no ways of making really high atomic number elements in usable quantities. A few atoms a second isn't going to be of any practical use.
 
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khorum

khorum

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Tuco said:
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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Except for the very rarest materials that are vanishingly scarce in Earth, it would almost always be waaaay more valuable in orbit. By the time a serious asteroid mining rush has begun, orbital manufacturing will already be further along. And bringing raw materials TO orbit will inevitably be more efficient because finished goods designed for orbital use will be more valuable than whatever use those resources would be applied on earth:

 
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LachiusTZ

LachiusTZ

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Meant to ask this the other day, but did you guys ever work out that math? Lol

Is it survivable?

Watched this when it came out, havent had the time to watch again. Prolly will this morning.


Guessing everyone here is pretty familiar with the guy.
 
Tuco

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LachiusTZ said:
Meant to ask this the other day, but did you guys ever work out that math? Lol

Is it survivable?

Watched this when it came out, havent had the time to watch again. Prolly will this morning.


Guessing everyone here is pretty familiar with the guy.
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Survivable in terms of a design existing that introduces fewer than 5gs onto a human occupant and offering substantial acceleration over a longish period of time? Yes that math can work out, but obviously the faster you go and the slower you accelerate the more mass and engineering you need to make it work. What doesn't work out is maintaining the velocity of the skyhook in any reasonable usage scenarios on earth, or maintaining it in the presence of atmosphere.

I believe the AEPS you linked before provides 1.77 Newtons of thrust Advanced Electric Propulsion System - Wikipedia

which means that if you had two of them on either ends of a skyhook they would with a mass at the end equivalent to a SpaceX starship (120,000kg), they'd accelerate at 0.00001475 m/s2.

If you wanted them to move at say, 2x low earth orbit speed ( say 16,000m/s) and then bring a spaceX Starship from a zero orbital speed to LEO speed by basically dropping half your speed into the starship, and then have the skyhook ends accelerate back to 2x LEO speed, you'd be able to do that kind of mission every ohhhhhhh.... 6277 days. And that's ignoring atmospheric drag.

Without equivalent mass entering Earth, the skyhook is DOA. You're just shifting the burden of fighting gravity to orbit where propellant is scarce instead of fighting gravity on earth where it's plentiful.

Note: I didn't double check any of my math, but it doesn't really matter because the end result to accelerate a skyhook is going to be "fucking forever". We don't have the tech to accelerate mass quickly without massive rockets. If we find a non-bullshit EMDrive or find a way to harvest ice from asteroids and turn that into rocket fuel, or do anything to turn 0.00001475 m/s2 into a much higher number, then things change. Dramatically.
 
khorum

khorum

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The thing is it's a solution for boosting things IN ATMOSPHERE into interplanetary velocities, which is pretty inefficient when you can do it for orders of magnitude less energy when you have a drag coefficient of zero. Once the mass you want to accelerate to Mars is already in orbit, then accelerating it via ion thrusters is probably competitive with the tether. In fact, it'll probably win out over longer distances and smaller payloads.

So the analysis should really be whether a surface-to-LEO shuttle and a transfer to ion/plasma drives is more efficient than the acquisition and maintenance costs of the tether. And I suspect the rockets+interplanetary shipping combo wins out.
 
LachiusTZ

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Depends on volume and nature. The tether is good for if we ever start bringing millions of tons down and taking millions of tons up.

Ion thrusters, not the ones I linked but possibly a later generation of the same, might be able to mitigate some of the imbalance between things going up vs going down.

In reality its just fodder for kessler syndrome here. Any large orbital structure is.

Doing it on Mars / Luna might be viable one day. Or somewhere in the asteroid belt to catch incoming ships and sling outgoing materials to Earth / Mars / Luna.

Tuco said:
Without equivalent mass entering Earth, the skyhook is DOA. You're just shifting the burden of fighting gravity to orbit where propellant is scarce instead of fighting gravity on earth where it's plentiful.
Click to expand...

Did you watch the video? Because that was part of it . . . Something like hall thrusters would be good for offsetting the imbalance. Not spinning the damn thing up.
 
Tuco

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LachiusTZ said:
Did you watch the video? Because that was part of it . . . Something like hall thrusters would be good for offsetting the imbalance. Not spinning the damn thing up.
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How does that video indicate the skyhook will maintain velocity as it's launching shit away from earth?

edit: we're probably saying the same thing
LachiusTZ said:
Depends on volume and nature. The tether is good for if we ever start bringing millions of tons down and taking millions of tons up.
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khorum

khorum

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They'd balance incoming and outgoing traffic to maintain momentum. The incoming mass would spin it up after it loses momentum sending stuff out. You'd need several of them to make it really work.

Something like the tether would be almost a necessity for mining asteroids, where the costs of the reaction mass to boost stuff back to Earth would eat away at the profits
 
C

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MusicForFish said:
Won't this throw a big wrench into the plan for moving towards habitation of space?
At least for a while?

Astronauts experienced reverse blood flow and blood clots on the space station, study says
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I'm sure the more we learn the more we'll realize that gravity is critical to long-term human health. (Which shouldn't be particularly surprising.) How much is needed to address health risks is obviously TBD, but long-term habitats will pretty clearly need spin or some other artificial G solution.

Radiation shielding is another significant hurdle.
 
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AladainAF

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This looked interesting.

www.upi.com

Sugars essential to life detected in meteorites, a first - UPI.com

For the first time, scientists have identified sugars essential to life inside meteorites.
www.upi.com www.upi.com

Article said:
Nov. 19 (UPI) -- For the first time, scientists have identified sugars essential to life inside meteorites.

The discovery, described this week in the journal PNAS, supports the theory that a bombardment of meteorites provided ancient Earth with the building blocks required for the origin of life.
Click to expand...
 
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meStevo

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Starship Mk1 has failed cyro pressure testing.

 
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C

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meStevo said:
Starship
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Interesting factoid about Starship I picked up from my cousin on the SpaceX factory tour. Most Starship manufacturing will have to be done near the launch site and not in Hawthorne because the diameter of the Starship design is too large to fit under the minimum overpass height on the US Interstate system. The Falcon Heavy is near some fundamental limits of current materials for components with that profile. I guess there are some benefits to shorter, fatter rockets which we've traditionally eschewed in favor of ground-based transportability.
 
Borzak

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All our stuff that was larger than 21' in diameter we made at the shop adjacent to the intracoastal waterway and just shipped it by barge. The other end was the customers problem lol.
 
khorum

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The switch from carbon composites to steel implicates welding quality as potential failure points all over the whole thing. Their original design was based on carbon fiber for all the pressure volumes, especially that lox tank, and they even built a couple for the BFR:

Spx2-980x611.jpg


The outer hull was gonna be carbon fiber too.
 
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