8 ms·

Can someone ELI5 how this Space Catapult should "theoretical" work?

gnode 8y ago
The article is very light on details, but I believe what's being proposed is an evacuated tube with maglev propulsion, used to accelerate a rocket up to 5000mph (as stated in the article) while on the ground. The rocket is then released, and travels until some altitude is reached, at which point engine then starts and it continues to orbit. This results in a large fuel saving over a conventional rocket. https://en.wikipedia.org/wiki/Mass_driver https://en.wikipedia.org/wiki/Mass_driver The g-forces involved would be very high, well beyond lethal to a human, so this would be for launching robust satellites, raw materials, or fuel cheaply into space. They would still be substantially lower than those of a space gun / intercontinental artillery. https://en.wikipedia.org/wiki/Space_gun#Practical_attempts https://en.wikipedia.org/wiki/Space_gun#Practical_attempts
- beinstein 8y ago
  No maglev and rocket fires at a different time :-)
  - gnode 8y ago
    Sorry, I didn't mean to imply this wasn't the case. I've edited this in now.
    - rory096 8y ago
      Given that the grandparent is presumably Ben Einstein of Bolt VC, an early investor in SpinLaunch, it sounds safe to say it's not using maglev at all. They say the catapult will be a centrifuge spinning inside a vacuum. https://www.crunchbase.com/person/ben-einstein https://www.crunchbase.com/person/ben-einstein https://www.crunchbase.com/funding_round/spinlaunch-convertible-note--39075185#section-investors https://www.crunchbase.com/funding_round/spinlaunch-converti...
- zer0faith 8y ago
  Would it be fair to say it is kinda like punkin chunkin? https://en.wikipedia.org/wiki/Pumpkin_chucking https://en.wikipedia.org/wiki/Pumpkin_chucking
  - gnode 8y ago
    Similar. I'd like to see a maglev (railgun) pumpkin chuck though.
stephengillie 8y ago
It shouldn't. A second push is needed up change direction from "away from Earth" to "going around Earth", because the atmosphere creates too much drag to get there in one push.
- JumpCrisscross 8y ago
  > the atmosphere creates too much drag to get there in one push This is not true. Feasibly designs have been worked out. The challenge is the trade off between cheap, short and high-G systems and expensive, long and low-G systems.
- cjensen 8y ago
  The second push has nothing to do with atmosphere. It's because orbits repeat. As soon as the push is done, you are in the initial orbit heading away from the surface. In other words, your initial orbit intersects the ground and it would be unwise to complete a full orbit. The second push converts the narrow ellipse of the initial orbit into a wider orbit which avoids the ground-penetrating aspect of the first orbit. The notion of sending volatile fuel sufficient to make the correction and yet somehow not kablooeying at launch seems like a hard problem to me.
  - stephengillie 8y ago
    The notion of using a catapult instead of a rocket for the first stage seems safer.
dvh 8y ago
Simple. You pitch the idea to the investor, promise big money in the future, you take small money now and use part of it to build some nonviable prototype, what's left is your profit.

The article is very light on details, but I believe what's being proposed is an evacuated tube with maglev propulsion, used to accelerate a rocket up to 5000mph (as stated in the article) while on the ground. The rocket is then released, and travels until some altitude is reached, at which point engine then starts and it continues to orbit. This results in a large fuel saving over a conventional rocket. https://en.wikipedia.org/wiki/Mass_driver https://en.wikipedia.org/wiki/Mass_driver The g-forces involved would be very high, well beyond lethal to a human, so this would be for launching robust satellites, raw materials, or fuel cheaply into space. They would still be substantially lower than those of a space gun / intercontinental artillery. https://en.wikipedia.org/wiki/Space_gun#Practical_attempts https://en.wikipedia.org/wiki/Space_gun#Practical_attempts

beinstein 8y ago
No maglev and rocket fires at a different time :-)
- gnode 8y ago
  Sorry, I didn't mean to imply this wasn't the case. I've edited this in now.
  - rory096 8y ago
    Given that the grandparent is presumably Ben Einstein of Bolt VC, an early investor in SpinLaunch, it sounds safe to say it's not using maglev at all. They say the catapult will be a centrifuge spinning inside a vacuum. https://www.crunchbase.com/person/ben-einstein https://www.crunchbase.com/person/ben-einstein https://www.crunchbase.com/funding_round/spinlaunch-convertible-note--39075185#section-investors https://www.crunchbase.com/funding_round/spinlaunch-converti...
zer0faith 8y ago
Would it be fair to say it is kinda like punkin chunkin? https://en.wikipedia.org/wiki/Pumpkin_chucking https://en.wikipedia.org/wiki/Pumpkin_chucking
- gnode 8y ago
  Similar. I'd like to see a maglev (railgun) pumpkin chuck though.

stephengillie 8y ago

It shouldn't. A second push is needed up change direction from "away from Earth" to "going around Earth", because the atmosphere creates too much drag to get there in one push.

JumpCrisscross 8y ago
> the atmosphere creates too much drag to get there in one push This is not true. Feasibly designs have been worked out. The challenge is the trade off between cheap, short and high-G systems and expensive, long and low-G systems.
cjensen 8y ago
The second push has nothing to do with atmosphere. It's because orbits repeat. As soon as the push is done, you are in the initial orbit heading away from the surface. In other words, your initial orbit intersects the ground and it would be unwise to complete a full orbit. The second push converts the narrow ellipse of the initial orbit into a wider orbit which avoids the ground-penetrating aspect of the first orbit. The notion of sending volatile fuel sufficient to make the correction and yet somehow not kablooeying at launch seems like a hard problem to me.
- stephengillie 8y ago
  The notion of using a catapult instead of a rocket for the first stage seems safer.

dvh 8y ago

Simple. You pitch the idea to the investor, promise big money in the future, you take small money now and use part of it to build some nonviable prototype, what's left is your profit.