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There are two limitations here, both of which are serious:

1) As LocalFluff says, atmosphere. Any velocity component from any sort of launch track is going to be basically horizontal. If you're in vacuum and the launch velocity is a good portion of orbital velocity this would be a good thing.

In atmosphere, though, there are twothree cases:

1a) A fairly low launch velocity, say Mach 1. The launch impulse is basically bled away in drag. You gained nothing but lost a lot of energy while your rocket turned from horizontal to vertical. (Something that rockets don't do well.)

1b) A medium launch velocity, say Mach 10. Things get even worse--you need to beef up your rocket to handle this and you'll still bleed most of the velocity to drag.

1c) A very high launch velocity, say Mach 40 (Yes, I realize this is above orbital velocity. You'll need to be well above orbital velocity to make up for drag losses.) This could actually be of some use. It's only for payloads that can tolerate a lot of gs, both because of the launcher and the brutal deceleration that will happen when it hits the atmosphere. You'll also need a beefy launch capsule to do this, but you get to orbit for only the cost of a circularization burn. If you have enough such cargo it might make sense.

2) You have a big problem with the strength of a rocket. Rockets are normally built like eggshells--strong against the intended load, very weak against forces they aren't going to encounter. You'll need to beef your rocket up substantially so it can survive sitting there on the launch cradle before someone pushes the button.

Beefing a rocket up isn't actually that expensive construction but it's extra weight--and the rocket equation is brutal indeed. Every extra pound holding your booster together is a pound that comes off your payload. You only want to go to these costs if there is a substantial benefit to be gained.

There are two limitations here, both of which are serious:

1) As LocalFluff says, atmosphere. Any velocity component from any sort of launch track is going to be basically horizontal. If you're in vacuum and the launch velocity is a good portion of orbital velocity this would be a good thing.

In atmosphere, though, there are two cases:

1a) A fairly low launch velocity, say Mach 1. The launch impulse is basically bled away in drag. You gained nothing but lost a lot of energy while your rocket turned from horizontal to vertical. (Something that rockets don't do well.)

1b) A medium launch velocity, say Mach 10. Things get even worse--you need to beef up your rocket to handle this and you'll still bleed most of the velocity to drag.

1c) A very high launch velocity, say Mach 40 (Yes, I realize this is above orbital velocity. You'll need to be well above orbital velocity to make up for drag losses.) This could actually be of some use. It's only for payloads that can tolerate a lot of gs, both because of the launcher and the brutal deceleration that will happen when it hits the atmosphere. You'll also need a beefy launch capsule to do this, but you get to orbit for only the cost of a circularization burn. If you have enough such cargo it might make sense.

2) You have a big problem with the strength of a rocket. Rockets are normally built like eggshells--strong against the intended load, very weak against forces they aren't going to encounter. You'll need to beef your rocket up substantially so it can survive sitting there on the launch cradle before someone pushes the button.

Beefing a rocket up isn't actually that expensive construction but it's extra weight--and the rocket equation is brutal indeed. Every extra pound holding your booster together is a pound that comes off your payload. You only want to go to these costs if there is a substantial benefit to be gained.

There are two limitations here, both of which are serious:

1) As LocalFluff says, atmosphere. Any velocity component from any sort of launch track is going to be basically horizontal. If you're in vacuum and the launch velocity is a good portion of orbital velocity this would be a good thing.

In atmosphere, though, there are three cases:

1a) A fairly low launch velocity, say Mach 1. The launch impulse is basically bled away in drag. You gained nothing but lost a lot of energy while your rocket turned from horizontal to vertical. (Something that rockets don't do well.)

1b) A medium launch velocity, say Mach 10. Things get even worse--you need to beef up your rocket to handle this and you'll still bleed most of the velocity to drag.

1c) A very high launch velocity, say Mach 40 (Yes, I realize this is above orbital velocity. You'll need to be well above orbital velocity to make up for drag losses.) This could actually be of some use. It's only for payloads that can tolerate a lot of gs, both because of the launcher and the brutal deceleration that will happen when it hits the atmosphere. You'll also need a beefy launch capsule to do this, but you get to orbit for only the cost of a circularization burn. If you have enough such cargo it might make sense.

2) You have a big problem with the strength of a rocket. Rockets are normally built like eggshells--strong against the intended load, very weak against forces they aren't going to encounter. You'll need to beef your rocket up substantially so it can survive sitting there on the launch cradle before someone pushes the button.

Beefing a rocket up isn't actually that expensive construction but it's extra weight--and the rocket equation is brutal indeed. Every extra pound holding your booster together is a pound that comes off your payload. You only want to go to these costs if there is a substantial benefit to be gained.

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There are two limitations here, both of which are serious:

1) As LocalFluff says, atmosphere. Any velocity component from any sort of launch track is going to be basically horizontal. If you're in vacuum and the launch velocity is a good portion of orbital velocity this would be a good thing.

In atmosphere, though, there are two cases:

1a) A fairly low launch velocity, say Mach 1. The launch impulse is basically bled away in drag. You gained nothing but lost a lot of energy while your rocket turned from horizontal to vertical. (Something that rockets don't do well.)

1b) A medium launch velocity, say Mach 10. Things get even worse--you need to beef up your rocket to handle this and you'll still bleed most of the velocity to drag.

1c) A very high launch velocity, say Mach 40 (Yes, I realize this is above orbital velocity. You'll need to be well above orbital velocity to make up for drag losses.) This could actually be of some use. It's only for payloads that can tolerate a lot of gs, both because of the launcher and the brutal deceleration that will happen when it hits the atmosphere. You'll also need a beefy launch capsule to do this, but you get to orbit for only the cost of a circularization burn. If you have enough such cargo it might make sense.

2) You have a big problem with the strength of a rocket. Rockets are normally built like eggshells--strong against the intended load, very weak against forces they aren't going to encounter. You'll need to beef your rocket up substantially so it can survive sitting there on the launch cradle before someone pushes the button.

Beefing a rocket up isn't actually that expensive construction but it's extra weight--and the rocket equation is brutal indeed. Every extra pound holding your booster together is a pound that comes off your payload. You only want to go to these costs if there is a substantial benefit to be gained.