[nichtich]

If there're a lot of these objects entering and leaving solar system every year, and suppose some day in the near future we can keep track of them all, can we use them for us to send out larger probes? We see a rock coming near us, and send out a probe to its path. And before the collision the probe create a buffer object at the rear end so that it wouldn't be totally destroyed. After that the probe can free ride for a while at a high speed and re-ignite when it decides to go a separate path.

[Cyphase]

Not sure about a buffer object, but a tether on a reel might work.

You harpoon the object, then let it pull the probe, giving lots of slack according to the engineering tolerances of the harpoon in the object (don't want it to come loose), the tether (don't want it to snap), the reel (don't want it to spin apart or get stuck or any one of a number of things), and the probe (don't want it damaged under extreme acceleration).

With enough tether and a low-enough-friction reel with magnetic bearings (think of the ungodly RPMs), you can accelerate the probe at almost any speed you'd like, within reason, although it would be best to accelerate as quickly as possible without risking. And remember that you only need to get the whole harpoon/tether/reel (HTR, or HiTchhikeR; you saw it here first) mechanism in range of the object as it passes by, so it can be bulkier than you would put on a probe moving under its own power. Or you could start off as usual, maybe with a gravity assist, which would allow for a less sophisticated HTR.

Then if you want to be clever, you can turn all those RPMs into stored energy. But that might not be worth the trouble.

[wallace_f]

Might be possible, but the tensile strength required may be beyond our material science capabilities.

A harpoon impacting an object going 26km/s would experience something like 12,000gs even if you gave it a 1km-long buffer.

So your harpoon would have to be rocket-assisted. The problem now is how long does your need to be? The tensile strength to carry the weight of the tether itself may make this impossible.

[Cyphase]

> Might be possible, but ... may be beyond our material science capabilities.

Certainly, for now and a while to come.

[wallace_f]

Perhaps some ultra-lightweight probe using some sophisticated ultra-strong elastic tethers may be a way to accelerate an object at an orders of magnitude greater speed using asteroids as counter-weights. Probably nothing strong-enough, though.

[simooooo]

I think the twisting of the body may also cause problems for the tether.

[wallace_f]

Hmm, accelerating such probe to the speed of the fastest man-made object ever made, Voyager 1 (17km/s), and using a 1-kilometer buffer object with linear acceleration with the asteroid (26km/s) we get >4,000gs.

What about elastic bands 100s of kms long? Probably no material strong enough, elastic or not.

[KnightOfWords]

There is no benefit to this I'm afraid. To take a ride on it you first have to match velocities, so you've already done the work to chase it down. Gravity assist maneuvers are the best option we currently have for launching probes into interstellar space: https://en.wikipedia.org/wiki/Gravity_assist