"Hitchiking" rocks?

[Scarecrow]

To equalize velocity with the target, your probe would have to expend all the energy to do so with thrust. Negating the advantage of trying to hitch a ride.

Assuming a strong enough teather and probe, you could launch such that the probe crosses behind the target body. At the probe's closest point, launch a teather at the target, and "rope swing" around the target to the right trajectory and release.

Point is, any attempt to change your velocity to match speed and direction of the target negates all advantage of "hitching" a ride.

In the above example of skitching a bus... imagine the bus traveling at 100mph and you are on a board crossing the street close to the bus. You have to either latch on and hope your arms don't get torn out, or speed up to nearly 100mph before grabbing on.

To continue the bus analogy, latching on and hoping your arms don't get torn out is pretty much what we (or at least I) propose. However, to make it less likely that our arms get torn out, we're making them really really stretchy. Think of "Elastigirl" from "The Incredibles".

 

[Linguofreak]

To equalize velocity with the target, your probe would have to expend all the energy to do so with thrust. Negating the advantage of trying to hitch a ride.

Well, given a sufficiently strong and long tether you could store the tether in a spool onboard. You would then grapple onto the asteroid, let the tether spool out, and use brakes on the spool to slow the spoolout speed (relatively) gradually. Those brakes would get really hot really fast, though, since you'd probably be trying to slow down from at least a few km/s with them...

 

[Sky Captain]

Is`t there a difference about roughly 50 km/s between Earth orbital velocity around the sun and orbital velocity of asteroid or comet traveling highly elliptical orbit? You would still have to reduce relative speed between the asteorid and probe to manageable level or your tether will explode on impact with asteorid. Slingshotting around the gas giants or having a good engine to gain velocity seems more practical ideas.

 

[escapetomsfate]

If there was a large enough object, wouldn't it be possible for the probe to pull itself into an orbit? It would use less fuel than matching velocities, probably. Or maybe even use a tether to slow the craft into an orbit of the object?

 

[Linguofreak]

Is`t there a difference about roughly 50 km/s between Earth orbital velocity around the sun and orbital velocity of asteroid or comet traveling highly elliptical orbit? You would still have to reduce relative speed between the asteorid and probe to manageable level or your tether will explode on impact with asteorid. Slingshotting around the gas giants or having a good engine to gain velocity seems more practical ideas.

Well, at a given radius, escape velocity = sqrt(2)*orbital velocity, so the difference would be a bit less than 15 km/s. (Earth's orbital velocity around the sun is 30 km/s, and the square root of two is about 1.4, which is a bit less than one and a half. So thirty km/s plus half of thirty km/s is a good approximation of solar escape velocity at Earth orbit).

Still, even at 3 km/s you're talking about getting rid of an energy equal to the yield of the probe's weight in TNT as the tether spools out. Now, you aren't going to be getting rid of it all at once as you would when you detonate the TNT, but it will still be quite a challenge. Probably much more reasonable just to match velocities with thrusters and forget about the tether.

 

[stosh]

Hitching rocks - Ultimate refuel

I found Orbiter through some SCI-FI RPG posts, so I have a great deal of interest in but not much more then high school physics and maths.

Anyway I seem to recall that some of the Earth crossing asteroids reach out to Mars or beyond. If some of the bodies were 'dead' comets they would be a great place to refuel as well as a great place for a station for science or otherwise.

Certainly there is a difference between the Near probe landing on EROS and hitching onto an object with a highly elliptical orbit. But if you could mine it while you are there, it would repay a lot of the dV you used to get there.

I think this would make a neat addon, maybe when I get the chance to play around with the developer tools.

Stosh