3 ms·

I think their basic idea is sound, it'll probably eventually function. My concerns are if it'll be worth it, since there's a trade-off being made between fuel m

I think their basic idea is sound, it'll probably eventually function. My concerns are if it'll be worth it, since there's a trade-off being made between fuel mass and heat shield mass, and at least based on Scott Manley's summary video this week, the rocket with the heat shield is close to the same mass as the Electron rocket. In which case I'm not sure the complexity of SpinLaunch is worth it. Edit: the video in question: https://www.youtube.com/watch?v=8Phy3n_S3ng https://www.youtube.com/watch?v=8Phy3n_S3ng and a more honest and detailed look at the company, again from Scott: https://www.youtube.com/watch?v=JAczd3mt3X0 https://www.youtube.com/watch?v=JAczd3mt3X0

gnramires 5y ago
I haven't seen Scott Manley's video; but if the mass cost of a heatshield is so significant that's a problem. However, there's a benefit in this case: heat shield probably scales with area (often something like mass^(2/3)), making it progressively less significant compared to fuel mass (which is roughly a constant fraction, i.e. it scales like mass^(1)). I think a high altitude launch site could make a significant difference as well (although that creates other logistic inconveniences). Atmospheric pressure approximately halves every 5km, and air resistance is roughly proportional to pressure.
- kurthr 5y ago
  Building and SpinLaunching at above 10k feet (3km) seems like a no-brainer. It reduces heating and weight while increasing terminal altitude substantially... like 2x. It would be more efficient, if they could use a whip effect to (match impedance) capture much more of the rotational energy they put into the spin, more like a trebuchet.
  - Schroedingersat 5y ago
    Is there any material strong enough to provide the whip? Or would you just make the spinning part slower?
  - sacrosancty 5y ago
    Is optimizing efficiency relevant at all? I'd think the electrical power cost must be negligible compared to the rest of the cost of a launch.
    - edrxty 5y ago
      It's not the electrical cost so much as system complexity. They could use less heat shield, more payload, spin the payload less hard, etc.
JumpCrisscross 5y ago
NASA can probably trade the tech, if it even barely works, for budget from the Pentagon. This is a ballistic launch system without the tell of a rocket burn.
- dotnet00 5y ago
  The Pentagon is already looking at them: https://spacenews.com/spinlaunch-joins-cadre-of-small-launch-companies-dod-wants-to-try-out/ https://spacenews.com/spinlaunch-joins-cadre-of-small-launch...

gnramires 5y ago

I haven't seen Scott Manley's video; but if the mass cost of a heatshield is so significant that's a problem. However, there's a benefit in this case: heat shield probably scales with area (often something like mass^(2/3)), making it progressively less significant compared to fuel mass (which is roughly a constant fraction, i.e. it scales like mass^(1)). I think a high altitude launch site could make a significant difference as well (although that creates other logistic inconveniences). Atmospheric pressure approximately halves every 5km, and air resistance is roughly proportional to pressure.

kurthr 5y ago
Building and SpinLaunching at above 10k feet (3km) seems like a no-brainer. It reduces heating and weight while increasing terminal altitude substantially... like 2x. It would be more efficient, if they could use a whip effect to (match impedance) capture much more of the rotational energy they put into the spin, more like a trebuchet.
- Schroedingersat 5y ago
  Is there any material strong enough to provide the whip? Or would you just make the spinning part slower?
- sacrosancty 5y ago
  Is optimizing efficiency relevant at all? I'd think the electrical power cost must be negligible compared to the rest of the cost of a launch.
  - edrxty 5y ago
    It's not the electrical cost so much as system complexity. They could use less heat shield, more payload, spin the payload less hard, etc.

JumpCrisscross 5y ago

NASA can probably trade the tech, if it even barely works, for budget from the Pentagon. This is a ballistic launch system without the tell of a rocket burn.

dotnet00 5y ago
The Pentagon is already looking at them: https://spacenews.com/spinlaunch-joins-cadre-of-small-launch-companies-dod-wants-to-try-out/ https://spacenews.com/spinlaunch-joins-cadre-of-small-launch...