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Realistically, what is the feasibility of a space catapult? I mean, the speed at ground level to be able to reach orbit must be insanely high, no? This high spe
by kuon 9y ago
Realistically, what is the feasibility of a space catapult? I mean, the speed at ground level to be able to reach orbit must be insanely high, no? This high speed in a thick atmosphere would cause all kind of heating problem on the catapult itself and the "rocket". I wonder what would be the actual numbers.
- rmcpherson 9y agoNot to mention the acceleration needed to achieve orbital velocity with a catapult. Seems like insanely high forces on the payload. I’d love to see how they solve this.
- pesmhey 9y agoIt’s a centrifuge, so the acceleration could be low enough to not cause damage to the payload.
- JoeAltmaier 9y agoSimply spinning is acceleration. Every been on a fast playground merry-go-round?
- pesmhey 9y agoYeah, you’re right! Wonder how they handle it then.
- JoeAltmaier 9y agoYou could embed the electronics in a resin - acceleration of a solid block would have fewer shear stresses inside the block.
- simooooo 9y agoSounds heavy
- deleted 9y ago[deleted]
- ecpottinger 9y agoNo it is not. Calculate the outward force of a centrifuge with 300 foot radius with a speed of 3000 MPH at the edge and you get a force of 2000G! Check your own numbers at: http://www.calctool.org/CALC/phys/newtonian/centrifugal http://www.calctool.org/CALC/phys/newtonian/centrifugal
- maxxxxx 9y agoAt around 50km radius you get 3g. That would be a pretty big centrifuge! Humans will probably never use this but maybe some types of satellites can handle the load.
- mhandley 9y agoYes, the centripetal acceleration only starts to get reasonable (ie less than 10g) with a 20km radius centrifuge. The only practical way to do that would be an evacuated circular tunnel equipped with a maglev. Maybe that's their solution?
- oh_sigh 9y agoThat's starting to sound like a hyperloop now
- justinpombrio 9y ago> Yes, the centripetal acceleration only starts to get reasonable (ie less than 10g) That's reasonable _for humans_. No one's going to launch a human by this thing, though, I hope.
- JoeAltmaier 9y agoLaunch from near the equator, high in the mountains? Chimborazo, Ecuador? At 6000 feet, its half the air pressure of sea level, and 1/4 the atmosphere to travel through. And accessible. A good start? https://www.google.com/maps/place/Chimborazo/@-1.4685873,-79.014542,11.22z/data=!4m5!3m4!1s0x91d372d7706a480b:0x69d5c66d2e629dff!8m2!3d-1.4693018!4d-78.8169396?hl=en https://www.google.com/maps/place/Chimborazo/@-1.4685873,-79...
- jsmthrowaway 9y agoGoing to space is not entirely about being high. It's about going sideways, fast. And if, at 6,000 feet, air pressure were half that of sea level, nobody would live in Denver and most Tibetans would be dead. Half is more like 6,000 meters.
- ceejayoz 9y agoGetting high quickly is important, which is why launch vehicles go up first, then do a gravity turn in thinner air, reducing drag and aerodynamic pressures on the vehicle. It's hard to go horizontally fast when you're fighting thick atmosphere. Air density at the top of Everest is 1/3 of sea level, and because of the Earth's shape, Chimborazo's 20,000 feet (6,000 meters) is actually further from the Earth's center than Everest, so half pressure sounds pretty reasonable: https://www.npr.org/templates/story/story.php?storyId=9428163 https://www.npr.org/templates/story/story.php?storyId=942816...
- 205guy 9y agoWhat you're forgetting is that the same mechanics that make Chimborazo the furthest from the earth's center (the oblate spheroid shape due to spin) also applies to the atmosphere (though probably to a different degree). So over Chimborazo, the atmosphere is also thicker, I'd imagine (could be more, could be less). I haven't looked at the actual measurements, but you might want to before you compare different latitudes. Also, see my other comment for non-engineering difficulties.
- 9y ago
- tensor_rank_0 9y agoif we assume our desired orbit to be at an altitude of 320 kilometers and our orbital velocity to be 7 kilometers per second; and we assume that air resistance decreases as a proportion of the cube of velocity inside the troposphere, proportional to the square of velocity inside the stratosphere, proportional to velocity inside the mesosphere, and discount air resistance above the mesosphere, we can begin to set up a differential equation to solve the problem. I'll be back, if anyone wants to follow along at home, post your answers when you are ready.
- ridgeguy 9y agoActual numbers, haven't tried to calculate. But the heat load due to atmospheric friction would be immense and immediate. The US built an antiballistic missile system that included a missile called Sprint [1]. It accelerated at 100G and developed temperatures of over 3000°C less than 5 seconds after launch. A video here [2]. It's a formidible engineering challenge to make a vehicle and payload that will survive such a difficult flight regime with commercially attractive economics. At this point, I don't understand SpinLaunch's advantage over earlier projectile systems (Gerald Bull) or current launchers like SpaceX. This will be interesting to follow. [1] https://en.wikipedia.org/wiki/Sprint_(missile) https://en.wikipedia.org/wiki/Sprint_(missile) [2] https://www.youtube.com/watch?v=msXtgTVMcuA https://www.youtube.com/watch?v=msXtgTVMcuA
- olliej 9y agoWorst case scenario the missile blows up on launch leveling the surroundings before the enemy missiles arrive, thus stealing the sense of achievement from them ;)