from Hacker News

SpinLaunch is building a centrifuge to launch satellites into orbit

by definetheword on 11/25/20, 12:31 AM with 143 comments

• by martey on 11/25/20, 6:03 AM

  The Wired article that this SyFy blurb is based on has more details (and more criticism) - https://www.wired.com/story/inside-spinlaunch-the-space-indu...

  > One former employee, who spoke on condition of anonymity due to their nondisparagement and nondisclosure contracts, acknowledged the gulf between theory and reality. They described SpinLaunch’s prototype centrifuge as a relatively unsophisticated machine that “any average engineering team could put together.” The employee said that scaling up to a functional suborbital launcher is going to be “very challenging” with SpinLaunch’s resources. The employee also cited the inexperience of some of the leaders. “The foresight to predict many of the issues that are going to happen was definitely lacking,” they said.

• by DennisP on 11/25/20, 1:31 AM

  I hope it works because it'd be rad, but at $500K per 200-lb payload, they'll cost $2500/lb. That's only half as much as SpaceX Rideshare for the same size payload, today. If Starship works out, then SpaceX costs will drop enormously.

  Fuel is a minor portion of launch cost. SpinLaunch is saving fuel but throwing away rockets; it's going to be hard to compete with someone who throws away more fuel but saves the rockets.

• by ogre_codes on 11/25/20, 4:13 AM

  > At this point the spacecraft will be subjected to a peak force 10,000 times greater than Earth's gravity, something opponents believe will seriously affect its structural integrity and the safety of its complex electronics.

  These kind of forces are pretty insane compared to even the high G boost you get on a normal rocket launch. I wonder if that is going to put a crimp on their potential client list.

• by hirundo on 11/25/20, 3:10 AM

  1. Build a large superconducting flywheel energy storage system like they have in Japan, right under the launch centrifuge.

  2. Use it continually to arbitrage energy prices. Buy low sell high.

  3. At launch time divert the rotational energy to the centrifuge. (I'd like to see that clutch.)

  4. Profit

• by nohat on 11/25/20, 2:26 AM

  Put this on the moon and we are talking. I'm not sure I see this being too useful otherwise, considering how much extra fairing mass those gforces are going to require

• by sneak on 11/25/20, 1:22 AM

  How does this prevent the satellite from being damaged when it transitions from 5000mph in vacuum centrifuge to less-than-5000mph-in-troposphere 1 meter later just out of the door?

  That's gotta be one hell of a fairing.

• by supernova87a on 11/25/20, 3:31 AM

  How does it deal with the sudden inrush of air and the object at supersonic speeds when the hatch is opened?

  Although, I guess for something about to go 5000 mph through the atmosphere, a little extra air probably isn't a big deal.

  Maybe the hatch cares though.

• by jl2718 on 11/25/20, 3:37 PM

  I think it’s possible with some tricks.

  The Mach angle is going to be extremely tight, so the profile of a normal spacecraft design would look like a flat plate at that speed. Normally, the craft is designed with a body shape roughly matching the Mach angle, but that would make it look like a long needle and you’d never be able to spin that up.

  So instead, you can use a hypersonic projectile to open up the pressure envelope in front of the payload. This would be a big chunk of tungsten in a tear-drop shape. In this case, the shape is not for laminar aerodynamics; it’s for keeping mass in front for positive ballistic coefficient, and maintaining the same shape as it erodes. This is required because it has to stay ahead of the payload. Of course you can also make a train of these increasing in width and spaced to match the pressure cone.

  The calculation for how much energy this takes is the sum of: 1. Mass to orbit. 2. The atmospheric pressure times the atmospheric height times the area of the Mach cone. 3. Heat losses. We can compute minimum values for the first two to get an idea of how much energy is required. I’m not sure about heat losses, but I think it’s roughly half the energy budget.

  Overall I’d naively expect this to end up being more efficient than carrying fuel to orbit.

• by mhandley on 11/25/20, 11:51 AM

  I couldn't help wondering what happens to the counterweight. 100kg travelling at 5000mph works out as about 500MJ. For comparison, 1 tonne of TNT is about 4.2GJ, so the energy of the counterweight is about the same as 120kg of TNT. Looks like stopping the counterweight will produce a pretty big explosion, but probably not their biggest problem.

• by mabbo on 11/25/20, 3:19 PM

  I have a hard time believing this is efficient in terms of energy.

  Air resistance is a function of the velocity squared and the air density. Air density is a non-linear function as well- it gets very thick near the ground.

  To put all your energy into maximizing your speed while you're at ground level (the spin launcher) you're wasting huge amounts of energy just pushing air out of the way. At hypersonic speeds, you'

  Rockets, by contrast, go their slowest at ground level and continually accelerate as they get higher. In SpaceX launches, they actually have a period where they throttle back as they go through "Max-Q", the highest aerodynamic pressure point, as it's more efficient to be slower until you're past this point.

  I guess using electrical energy, which is a much cheaper source than chemicals like rocket fuel, makes the payoff worthwhile? I dunno, I'm skeptical.

  Oh also you can only launch this somewhere that no one around will mind an insane sonic boom at ground level.

• by ganonm on 11/25/20, 9:49 AM

  I'm not really convinced nor reassured by their supposed tests to prove the physics will work. The test involving the iPhone? That's like saying "well, a marshmallow can withstand 1g of forces without being crushed therefore I can build a 3 story apartment building out of them".

• by bob1029 on 11/25/20, 10:35 AM

  10000g peak forces are a bit of a mess for space travel.

  Perhaps instead of directly spinning the object up to speed and "letting go", you could build up all of the energy into a heavy rotating mass which then imparts it into the spacecraft over a slightly longer timeframe via some simple mechanical clutch and cable arrangement. You would still have very strong g-forces, but you could control the impulse curve over time to spread out the forces better.

  Steel cables, flywheels and other members aren't going to care about such forces as much as the delicate electronics on board a spacecraft. Let these parts do the heavy lifting and then transmit the energy into the spacecraft in a methodical manner. You need to decouple the extreme nature of this sort of energy storage system from the spacecraft until it is go time.

• by beervirus on 11/25/20, 1:30 AM

  “The reason it's hard to get to orbit isn't that space is high up. It's hard to get to orbit because you have to go so fast.”

  https://what-if.xkcd.com/58/

  Sounds like this solves the easy part (getting to high altitude), but makes the hard part (getting to orbital velocity) even harder.

• by ivirshup on 11/25/20, 4:19 AM

  10,000g sounds pretty rough. Are there any existing electronics that we would expect to survive this?

• by andrewflnr on 11/25/20, 5:03 AM

  From the title, I was hoping this would be about a slingatron. That's still one of my favorite space launch proposals (the launch loop is another), but I wasn't able to quickly find a good reference. :(

• by ahaferburg on 11/26/20, 9:43 AM

  Does the rocket somehow counter the spin of the tether? If it's rigidly attached to the tether, I don't understand how it would stop spinning after being released. The rocket itself would spin very quickly, and due to conservation of angular momentum it would keep spinning upon release. Am I missing something?

  Or do they somehow counter the spinning of the tether, so that the rocket's orientation remains static? If there's another bearing at the attachment point, I don't see how just the outer bearing would withstand the friction at 10000g.

• by black6 on 11/25/20, 2:35 AM

  The Lofstrom Launch Loop[0] is less fanciful than a 5000 mph centrifuge slinging payloads into LEO.

  0: http://launchloop.com/

• by baltbalt on 11/25/20, 11:13 AM

  I hope they actually try, it's going to be a hell of a show.

• by rcgorton on 11/27/20, 7:44 PM

  It seems to require a vacuum to spin. And then it needs to launch at Hypersonic speeds and then meets atmosphere. Instant encounter with a solid barrier == blow-up. I am thoroughly skeptical about the technology both on the incredible G forces, and then hitting atmosphere at huge rates of speed.

• by elihu on 11/25/20, 5:54 AM

  I wonder what the cost/benefit of using a centrifuge is versus a light gas gun?

  https://en.wikipedia.org/wiki/Light-gas_gun

• by jccalhoun on 11/25/20, 3:33 PM

  I'm skeptical but I hope they can at least get a test launch or two out. I've always found things like this or using a slingshot to launch something to be interesting ideas and would love to see them tried out.

• by JoeAltmaier on 11/25/20, 8:20 PM

  Is it necessary to survive 10000g to get to orbit? Wrong question. It requires 17600mph to stay in orbit. However you do that. The g's to do that depend entirely on how long the acceleration is applied.

• by basicplus2 on 11/25/20, 6:29 AM

  I think it would be more practical to build a helium filled temporary plastic tunnel around a rail gun over a few miles with a gradual curve up at the end so humans could use it.

• by mensetmanusman on 11/25/20, 12:40 PM

  This lesson describes the fictitious ‘force’ used in this technology:

  https://youtu.be/rtFnki476cU

• by absolutelyrad on 11/25/20, 4:14 AM

  Ambitious. Not sure how it deals with the structural impact due to extreme forces.

• by Jemm on 11/25/20, 1:38 PM

  So Wired is now Popular Mechanics and Omni.

• by mlindner on 11/25/20, 9:05 AM

  It amazes me how many people fall for such ridiculous physics-defying nonsense. I guess this works to deprive fools of their money.

• by raphar on 11/25/20, 7:47 PM

  Ultimate trebuchet!

• by b34r on 11/25/20, 5:33 AM

  I’d rather see them launch junk toward the sun with it.