[jetbooster]

(Edit: these two paragraphs assume you want to put your rocket into earth orbit, which I realised you might not be attempting.)

No matter how you spin it, if you want these two rockets to go in exactly opposite directions and meet up again, The point at which they meet would _not_ be partially sideways and partially "up" (away from the earth). at the point where they meet, they would be going 100% parallel to the ground, and 180degrees from each other (ie, direct head-on collision).

This is ignoring the fact that minimal stable orbital velocity (the minimum speed for your rockets to go 'around' the planet, is about 7.8km/s, or 17 thousand miles per hour. and because they're going in opposite directions, thats 34 thousand miles per hour of effective collision speed.

Now, if you're suggesting instead, a full 'escape' velocity from the earth that allows them to both enter parabolic trajectories, and meet at some arbitrary point in the distance, I hope you've thought of a way to allow your two spacecraft to survive an explosion that launches them from 0 m/s relative to each other to roughly 22km/s relative to each other (49 thousand mph), in some semi-instantaneous event. If we assume this 'push' from each other happens over 10seconds (this is generous), that's gaining 2.2km/s/s, which is 224G for 10 seconds.

[cousin_it]

I'm talking about flying away from the Earth. And yeah, it's making a more theoretical point. All it proves is that "recapturing propellant", so to speak, is possible in principle - it's not prohibited by conservation of energy or momentum or whatever. Like sailing against the wind faster than the wind. Given that, there are probably more efficient ways to exploit this.

[jetbooster]

You'd still need to get your spaceship pair into an orbit (or at least a sharp sub-orbital hop) in order to excecute your plan though. the spaceship pair wouldn't just hang there in space. Also, it's simply not possible to mechanically push the two ships away from each other with sufficient velocity, and I imagine the explosives needed to blast your two ships apart would be better used in a smaller slower controlled explosion, often called a rocket engine.

There isn't a 'hack' for defeating orbital mechanics sadly. It takes expenditure of energy, and significant amounts of it.

[cousin_it]

I don't imagine using explosives for it. More like one ship is a railgun and the other a projectile. Then when they meet again, they can convert their leftover relative velocity back to electricity, by having the railgun catch the projectile and charge up.

Or the two ships could be a spinning pair tied by a cable, and then the cable is severed. To make a fast spinning pair, start two spinning pairs in parallel planes and opposite directions, and make them accelerate against each other electrically.

There are probably objections to those too, like size of railguns and strength of cables, and then engineering can find answers to that, and so on.

[plasticchris]

It doesn’t work - when combining the velocities sum to zero. Redirecting them in up isn’t free, it needs additional energy.