8 ms·

Also, if I'm reading Wikipedia right, delta v to LEO is 10km/sec, and that's not counting the insane atmospheric drag on something travelling that speed at sea

Also, if I'm reading Wikipedia right, delta v to LEO is 10km/sec, and that's not counting the insane atmospheric drag on something travelling that speed at sea level. Good luck.

msandford 13y ago
So assume 1000 meters in diameter and 15km/sec for giggles. a = v^2 / r = 15,000 x 15,000 / 500 = 450,000 m/sec^2 or 45,000g. It's on the same order of magnitude as the previous calcs. That's obviously also a big engineering challenge because it's freaking HUGE, especially for the precision required. The really great thing about going super-super fast is that at 15km/sec you're in space in ~10 seconds. Obviously you're going to start scrubbing speed really fast since drag is proportional to velocity squared. But you can evacuate the whole launch assembly and put some kind of an explosively opened door at the exit point and maintain your speed up until the last second.
- astrodust 13y ago
  The amount of drag during the acceleration phase is going to be inconsequential compared to tearing through the entire atmosphere at an angle.
  - chii 13y ago
    what if you launched two vehiucles, but the first vehicle is more like a bullet that disintegrates and causes a wake in front for the second vehicle to pass thru with less drag?
    - astrodust 13y ago
      That still involves sending the first at the requisite speed, and any drafting you might get is limited at best. It'd also leave a highly unstable wake trail, as any object ripping through the air at 7-8km/s is going to tear things up.
    - msandford 13y ago
      As soon as the first one hits the air it starts to slow down. The second one, as it's hauling ass through the wake, doesn't slow down. The difference in speeds gets very big, very quickly. As such the second one, the payload, would find itself smashing into the first one in short order.
      - scotty79 13y ago
        Since this thing can launch stuff continously maybe you could lunch few hundreds punchers to push air aside before the actual payload.
        bradleyland 13y ago
        It doesn't matter how many you send. If your scenario relies on the fact that the last in line must be the fastest of the group, it's always going to run in to the object directly in front of it.
        scotty79 13y ago
        I was imagining air behaving like water. If you send first projectile it'll slow down but move some water to the sides. Second will slow down less so it'll catch up with the first one but it will also push some water to the sides. Third also will catch up with the previous ones but each subsequent one will get farther as it travels through space punched out by previous ones. I don't think it's practical in any manner but I think such brute-forcing stream of projectiles out of atmosphere by literally punching hole in it might be nice to look at.
astrodust 13y ago
Since it's such a crazy idea, why not build a gigantic dirigible to take it up to high altitude? No problem, right?
- msandford 13y ago
  I love it!
- diziet 13y ago
  Because what matters for getting into space / orbit is velocity to achieve orbit. An object without that velocity will simply fall down to earth instead of orbiting. https://en.wikipedia.org/wiki/Orbit https://en.wikipedia.org/wiki/Orbit
  - msandford 13y ago
    I believe his suggestion is to use the dirigible to lift the Slingatron into the high atmosphere where the tremendous atmospheric drag will be substantially reduced, thus making a crazy idea slightly less crazy and at the same time, more crazy.
    - jamesaguilar 13y ago
      All I can say is I love the kind of crazy going on in this thread and all of you should buy kerbal space program.
    - bradleyland 13y ago
      Newton's third law gets in the way of that proposal. When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction to that of the first body. If you plan to generate acceleration using mechanical force like the reference design, you'd need a massive counterweight. An equal and opposite energy would be transferred to the counterweight, so you need a lot of mass, which would require an even more massive dirigible. You also need somewhere to dissipate that energy. In the reference design, the Earth is used as the counterweight. Alternatively, you could generate the circular motion using something like a rocket engine, in which case you might as well just use a rocket for linear acceleration and ditch the gyration mechanism.
Tloewald 13y ago
You would, i assume, build the real thing on an equatorial mountain.
daniel-cussen 13y ago
In the video, they address that you would still need a rocket both to circularize your orbit, and possibly recover kinetic energy lost in the atmosphere.

Also, if I'm reading Wikipedia right, delta v to LEO is 10km/sec, and that's not counting the insane atmospheric drag on something travelling that speed at sea level. Good luck.

msandford 13y ago

So assume 1000 meters in diameter and 15km/sec for giggles. a = v^2 / r = 15,000 x 15,000 / 500 = 450,000 m/sec^2 or 45,000g. It's on the same order of magnitude as the previous calcs. That's obviously also a big engineering challenge because it's freaking HUGE, especially for the precision required. The really great thing about going super-super fast is that at 15km/sec you're in space in ~10 seconds. Obviously you're going to start scrubbing speed really fast since drag is proportional to velocity squared. But you can evacuate the whole launch assembly and put some kind of an explosively opened door at the exit point and maintain your speed up until the last second.

astrodust 13y ago
The amount of drag during the acceleration phase is going to be inconsequential compared to tearing through the entire atmosphere at an angle.
- chii 13y ago
  what if you launched two vehiucles, but the first vehicle is more like a bullet that disintegrates and causes a wake in front for the second vehicle to pass thru with less drag?
  - astrodust 13y ago
    That still involves sending the first at the requisite speed, and any drafting you might get is limited at best. It'd also leave a highly unstable wake trail, as any object ripping through the air at 7-8km/s is going to tear things up.
  - msandford 13y ago
    As soon as the first one hits the air it starts to slow down. The second one, as it's hauling ass through the wake, doesn't slow down. The difference in speeds gets very big, very quickly. As such the second one, the payload, would find itself smashing into the first one in short order.
    - scotty79 13y ago
      Since this thing can launch stuff continously maybe you could lunch few hundreds punchers to push air aside before the actual payload.
      - bradleyland 13y ago
        It doesn't matter how many you send. If your scenario relies on the fact that the last in line must be the fastest of the group, it's always going to run in to the object directly in front of it.
        scotty79 13y ago
        I was imagining air behaving like water. If you send first projectile it'll slow down but move some water to the sides. Second will slow down less so it'll catch up with the first one but it will also push some water to the sides. Third also will catch up with the previous ones but each subsequent one will get farther as it travels through space punched out by previous ones. I don't think it's practical in any manner but I think such brute-forcing stream of projectiles out of atmosphere by literally punching hole in it might be nice to look at.

astrodust 13y ago

Since it's such a crazy idea, why not build a gigantic dirigible to take it up to high altitude? No problem, right?

msandford 13y ago
I love it!
diziet 13y ago
Because what matters for getting into space / orbit is velocity to achieve orbit. An object without that velocity will simply fall down to earth instead of orbiting. https://en.wikipedia.org/wiki/Orbit https://en.wikipedia.org/wiki/Orbit
- msandford 13y ago
  I believe his suggestion is to use the dirigible to lift the Slingatron into the high atmosphere where the tremendous atmospheric drag will be substantially reduced, thus making a crazy idea slightly less crazy and at the same time, more crazy.
  - jamesaguilar 13y ago
    All I can say is I love the kind of crazy going on in this thread and all of you should buy kerbal space program.
  - bradleyland 13y ago
    Newton's third law gets in the way of that proposal. When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction to that of the first body. If you plan to generate acceleration using mechanical force like the reference design, you'd need a massive counterweight. An equal and opposite energy would be transferred to the counterweight, so you need a lot of mass, which would require an even more massive dirigible. You also need somewhere to dissipate that energy. In the reference design, the Earth is used as the counterweight. Alternatively, you could generate the circular motion using something like a rocket engine, in which case you might as well just use a rocket for linear acceleration and ditch the gyration mechanism.

Tloewald 13y ago

You would, i assume, build the real thing on an equatorial mountain.

daniel-cussen 13y ago

In the video, they address that you would still need a rocket both to circularize your orbit, and possibly recover kinetic energy lost in the atmosphere.