3 ms·

Very interesting. Is it possible to make a trebuchet that can throw stuffs beyond escape velocity?

0xBA5ED 8y ago
Probably not exactly what you had in mind, but there's something called a skyhook which might act kind of like an orbital trebuchet. https://en.wikipedia.org/wiki/Skyhook_(structure) https://en.wikipedia.org/wiki/Skyhook_(structure)
- herbstein 8y ago
  Video going into detail on Skyhooks: https://youtu.be/TlpFzn_Y-F0 https://youtu.be/TlpFzn_Y-F0
NickNameNick 8y ago
The closest thing I can think of is the 'slingatron'. https://en.m.wikipedia.org/wiki/Non-rocket_spacelaunch https://en.m.wikipedia.org/wiki/Non-rocket_spacelaunch
rebuilder 8y ago
Naively, I'd think a simple lever could do that, but it becomes a materials science problem: with no constraints on the length of the lever lenght, and no constraints in the density of the counterweight, you should be able to achieve any velocity, right? Well, up to where relativistic effects become an impediment, of course. The question is, is it possible to create such materials as this would require? As you can probably guess, I'm not a physicist. Maybe someone with expertise can chime in here.
- masklinn 8y ago
  > Well, up to where relativistic effects become an impediment, of course. I don't think relativistic effect would enter the equation for escape velocity (there's a 5 orders of magnitude difference), your issue will be basic material science, namely: * That you'll need to add enough headroom that the payload is still at escape velocity after going through the atmosphere, which means the projectile needs to be launched way beyond escape velocity in a very dense atmosphere. Which means it will instantly burn up / blow up as it leaves the launch system, probably alongside the sling and part of the arm… * except for the counterweight and material rigidity you need for the arm to not be feasible either, you'd need a long arm multiple miles long and a counterweight in the megaton range… before even accounting for the length of the long arm itself, or how you'll actually bring the bloody arm down
deleted 8y ago
[deleted]
ColinWright 8y ago
Orbital Velocity at grazing altitude is 8 km/s, and escape velocity is sqrt(2) times that, or about 11.3 km/s. Thing is, anything travelling that fast in the atmosphere tries to turn to plasma, so your launch arm would need to be a bit special. Or at very high altitude. Or have ablative heat shielding. But atmospheric drag would probably prevent you from getting anything like those speeds with this kind of mechanism.
- ygra 8y ago
  So on the moon it might work ;)
  - ColinWright 8y ago
    Vacuum helps, certainly. Also the escape velocity on the Moon is about 2.4 km/s. That's still rather fast ...
- dividuum 8y ago
  This happened before: https://en.wikipedia.org/wiki/Operation_Plumbbob#Propulsion_of_steel_plate_cap https://en.wikipedia.org/wiki/Operation_Plumbbob#Propulsion_...
  - craftyguy 8y ago
    Wow, so they basically made a cannon powered by 300t nuclear explosion.
- wallace_f 8y ago
  It has been researched: >"In Project HARP, a 1960s joint United States and Canada defence project, a U.S. Navy 16 in (410 mm) 100 caliber gun was used to fire a 180 kg (400 lb) projectile at 3600 m/s or 12,960 km/h (8,050 mph), reaching an apogee of 180 km (110 mi), hence performing a suborbital spaceflight. However, a space gun has never been successfully used to launch an object into orbit or out of Earth's gravitational pull."
anotheryou 8y ago
maybe these guys are planning that https://techcrunch.com/2018/02/22/spinlaunch-2/ https://techcrunch.com/2018/02/22/spinlaunch-2/

Probably not exactly what you had in mind, but there's something called a skyhook which might act kind of like an orbital trebuchet. https://en.wikipedia.org/wiki/Skyhook_(structure) https://en.wikipedia.org/wiki/Skyhook_(structure)

herbstein 8y ago
Video going into detail on Skyhooks: https://youtu.be/TlpFzn_Y-F0 https://youtu.be/TlpFzn_Y-F0

NickNameNick 8y ago

The closest thing I can think of is the 'slingatron'. https://en.m.wikipedia.org/wiki/Non-rocket_spacelaunch https://en.m.wikipedia.org/wiki/Non-rocket_spacelaunch

rebuilder 8y ago

Naively, I'd think a simple lever could do that, but it becomes a materials science problem: with no constraints on the length of the lever lenght, and no constraints in the density of the counterweight, you should be able to achieve any velocity, right? Well, up to where relativistic effects become an impediment, of course. The question is, is it possible to create such materials as this would require? As you can probably guess, I'm not a physicist. Maybe someone with expertise can chime in here.

masklinn 8y ago
> Well, up to where relativistic effects become an impediment, of course. I don't think relativistic effect would enter the equation for escape velocity (there's a 5 orders of magnitude difference), your issue will be basic material science, namely: * That you'll need to add enough headroom that the payload is still at escape velocity after going through the atmosphere, which means the projectile needs to be launched way beyond escape velocity in a very dense atmosphere. Which means it will instantly burn up / blow up as it leaves the launch system, probably alongside the sling and part of the arm… * except for the counterweight and material rigidity you need for the arm to not be feasible either, you'd need a long arm multiple miles long and a counterweight in the megaton range… before even accounting for the length of the long arm itself, or how you'll actually bring the bloody arm down

deleted 8y ago

[deleted]

ColinWright 8y ago

Orbital Velocity at grazing altitude is 8 km/s, and escape velocity is sqrt(2) times that, or about 11.3 km/s. Thing is, anything travelling that fast in the atmosphere tries to turn to plasma, so your launch arm would need to be a bit special. Or at very high altitude. Or have ablative heat shielding. But atmospheric drag would probably prevent you from getting anything like those speeds with this kind of mechanism.

ygra 8y ago
So on the moon it might work ;)
- ColinWright 8y ago
  Vacuum helps, certainly. Also the escape velocity on the Moon is about 2.4 km/s. That's still rather fast ...
dividuum 8y ago
This happened before: https://en.wikipedia.org/wiki/Operation_Plumbbob#Propulsion_of_steel_plate_cap https://en.wikipedia.org/wiki/Operation_Plumbbob#Propulsion_...
- craftyguy 8y ago
  Wow, so they basically made a cannon powered by 300t nuclear explosion.
wallace_f 8y ago
It has been researched: >"In Project HARP, a 1960s joint United States and Canada defence project, a U.S. Navy 16 in (410 mm) 100 caliber gun was used to fire a 180 kg (400 lb) projectile at 3600 m/s or 12,960 km/h (8,050 mph), reaching an apogee of 180 km (110 mi), hence performing a suborbital spaceflight. However, a space gun has never been successfully used to launch an object into orbit or out of Earth's gravitational pull."

anotheryou 8y ago

maybe these guys are planning that https://techcrunch.com/2018/02/22/spinlaunch-2/ https://techcrunch.com/2018/02/22/spinlaunch-2/