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According to Elon Musk [1], the first stage could technically fly all the way to orbit (if it weren't lifting the rest of the rocket); it just wouldn't be able

According to Elon Musk [1], the first stage could technically fly all the way to orbit (if it weren't lifting the rest of the rocket); it just wouldn't be able to carry a useful payload. [1] https://twitter.com/elonmusk/status/669132749500887040 https://twitter.com/elonmusk/status/669132749500887040

stcredzero 9y ago
So throw some advanced carbon fiber construction at it and launch it from a mass driver. Then you'd have an SSTO with a small usable payload!
- sitharus 9y ago
  Something that can withstand the acceleration of a mass driver and the accompanying atmospheric heating while still being light enough to achieve orbit would be quite the feat.
  - brianwawok 9y ago
    Would hybrid help? Say mass driver to 1000 m/s before the rocket booster starts?
- TheSpiceIsLife 9y ago
  You made it sound easy. The tallest building is about 830m high. A rocket would have to undergo some fierce acceleration to gain any useful speed over that distance. Something like pushing a bullet through water. The stresses on such a structure, and the launch vehicle, would probably give them a limited life span. I suspect economics plays a big role here. I suspect it is cheaper to launch multistage rockets than to build a mass driver long / tall enough to be useful.
  - kevin_thibedeau 9y ago
    Why do you think Musk is investing in tunneling? Hyperloops are a nice cover for something much more practical.
  - njarboe 9y ago
    With mountains and tunnels you can have a much longer runway. Maybe Musk's SpaceX and Boring companies can have a joint venture. With Everest at about 9000m and the deepest mine at 4000m that would give you 13000 meters. Maybe you could dig deeper or curve the track for an even greater launch distance and less peak acceleration.
  - stcredzero 9y ago
    The tallest building is about 830m high. Theoretical max height for a building using conventional skyscraper techniques is 11 miles, at which point it's ridiculously expensive. Someone at JPL did a work up of using columns made out of ultra pressurized boron balloon tanks, and found that 100km is actually possible, though also ridiculously expensive. A rocket would have to undergo some fierce acceleration to gain any useful speed over that distance. To convert a Falcon 1st stage into a cheat-SSTO, all you need to do is to lighten it a bit and give it a bit of a boost. Such is the nasty nature of the rocket equation. You have to accelerate the fuel you need to accelerate the fuel. So by "cheating" with accelerating the fully loaded rocket, you save a lot of fuel weight for the same final delta-v. Due to the same nasty mathematics, this translates to a tiny payload, of course. I suspect economics plays a big role here. I suspect it is cheaper to launch multistage rockets than to build a mass driver long / tall enough to be useful. Yadda yadda. Yes, this comes up in just about every discussion like this. It's just neat to think about what else you could do with a Falcon 1st stage. I mean, would you turn down a single stage vehicle you could take into orbit? It would make an extravagant billionaire's toy. Actually, this general sort of scheme does have a practical use. Modify a methane-oxygen fueled 1st stage so that it could make it to a somewhat higher orbit, but still have payload for a docking and remote maneuvering system. Then have the empty tanks dock with each other to create a space station with tons of internal space. You couldn't do this with the Falcon 9, as it uses RP-1, but methane and oxygen would just boil off into vacuum.
ChuckMcM 9y ago
And that answers my question. Interesting concept in that twitter feed to launch "boosters" to orbit, refill on orbit and then use them as space tugs between earth and moon. Of course 'on orbit refill' is like Toyota's "first remove the engine" step on Camry timing belt changes. Short easy to say step, encapsulating a whole lot of work and engineering.
- greglindahl 9y ago
  Lockheed Martin's CRS-2 losing bid involved an upper stage which could be refueled and repeatedly used. Apparently it was way too expensive. But on-orbit refill: not only has ISS been refueled by numerous vehicles, but China just did it to their new space station. I see people saying it's hard all the time, but no one explaining if this ISS thing is inefficient or something.
  - ChuckMcM 9y ago
    It has been my understanding that the ISS doesn't "refuel", rather the attached crew transport vehicle (the shuttle and now only the Soyuz) used their thrusters to boost its orbit. Searching for information on this I found this Quora answer (https://www.quora.com/How-does-and-how-often-does-the-ISS-have-to-refuel-in-order-to-maintain-enough-fuel-to-burn-its-thrusters https://www.quora.com/How-does-and-how-often-does-the-ISS-ha...) which suggested there had been one test refueling. I think you saw the same ULA presentation I did, they seemed to think it was very difficult and didn't mention the ISS at all as I recall.
- Tharkun 9y ago
  Why can't we strap two F9s to a Space Shuttle and recover them?
  - brianwawok 9y ago
    The cost of the space shuttle flight would be about 50x what you recovered. Useful maybe to get a science experiment back but not to reduce launch cost.
- 9y ago

stcredzero 9y ago

So throw some advanced carbon fiber construction at it and launch it from a mass driver. Then you'd have an SSTO with a small usable payload!

sitharus 9y ago
Something that can withstand the acceleration of a mass driver and the accompanying atmospheric heating while still being light enough to achieve orbit would be quite the feat.
- brianwawok 9y ago
  Would hybrid help? Say mass driver to 1000 m/s before the rocket booster starts?
TheSpiceIsLife 9y ago
You made it sound easy. The tallest building is about 830m high. A rocket would have to undergo some fierce acceleration to gain any useful speed over that distance. Something like pushing a bullet through water. The stresses on such a structure, and the launch vehicle, would probably give them a limited life span. I suspect economics plays a big role here. I suspect it is cheaper to launch multistage rockets than to build a mass driver long / tall enough to be useful.
- kevin_thibedeau 9y ago
  Why do you think Musk is investing in tunneling? Hyperloops are a nice cover for something much more practical.
- njarboe 9y ago
  With mountains and tunnels you can have a much longer runway. Maybe Musk's SpaceX and Boring companies can have a joint venture. With Everest at about 9000m and the deepest mine at 4000m that would give you 13000 meters. Maybe you could dig deeper or curve the track for an even greater launch distance and less peak acceleration.
- stcredzero 9y ago
  The tallest building is about 830m high. Theoretical max height for a building using conventional skyscraper techniques is 11 miles, at which point it's ridiculously expensive. Someone at JPL did a work up of using columns made out of ultra pressurized boron balloon tanks, and found that 100km is actually possible, though also ridiculously expensive. A rocket would have to undergo some fierce acceleration to gain any useful speed over that distance. To convert a Falcon 1st stage into a cheat-SSTO, all you need to do is to lighten it a bit and give it a bit of a boost. Such is the nasty nature of the rocket equation. You have to accelerate the fuel you need to accelerate the fuel. So by "cheating" with accelerating the fully loaded rocket, you save a lot of fuel weight for the same final delta-v. Due to the same nasty mathematics, this translates to a tiny payload, of course. I suspect economics plays a big role here. I suspect it is cheaper to launch multistage rockets than to build a mass driver long / tall enough to be useful. Yadda yadda. Yes, this comes up in just about every discussion like this. It's just neat to think about what else you could do with a Falcon 1st stage. I mean, would you turn down a single stage vehicle you could take into orbit? It would make an extravagant billionaire's toy. Actually, this general sort of scheme does have a practical use. Modify a methane-oxygen fueled 1st stage so that it could make it to a somewhat higher orbit, but still have payload for a docking and remote maneuvering system. Then have the empty tanks dock with each other to create a space station with tons of internal space. You couldn't do this with the Falcon 9, as it uses RP-1, but methane and oxygen would just boil off into vacuum.

ChuckMcM 9y ago

And that answers my question. Interesting concept in that twitter feed to launch "boosters" to orbit, refill on orbit and then use them as space tugs between earth and moon. Of course 'on orbit refill' is like Toyota's "first remove the engine" step on Camry timing belt changes. Short easy to say step, encapsulating a whole lot of work and engineering.

greglindahl 9y ago
Lockheed Martin's CRS-2 losing bid involved an upper stage which could be refueled and repeatedly used. Apparently it was way too expensive. But on-orbit refill: not only has ISS been refueled by numerous vehicles, but China just did it to their new space station. I see people saying it's hard all the time, but no one explaining if this ISS thing is inefficient or something.
- ChuckMcM 9y ago
  It has been my understanding that the ISS doesn't "refuel", rather the attached crew transport vehicle (the shuttle and now only the Soyuz) used their thrusters to boost its orbit. Searching for information on this I found this Quora answer (https://www.quora.com/How-does-and-how-often-does-the-ISS-have-to-refuel-in-order-to-maintain-enough-fuel-to-burn-its-thrusters https://www.quora.com/How-does-and-how-often-does-the-ISS-ha...) which suggested there had been one test refueling. I think you saw the same ULA presentation I did, they seemed to think it was very difficult and didn't mention the ISS at all as I recall.
Tharkun 9y ago
Why can't we strap two F9s to a Space Shuttle and recover them?
- brianwawok 9y ago
  The cost of the space shuttle flight would be about 50x what you recovered. Useful maybe to get a science experiment back but not to reduce launch cost.
9y ago