"Hitchiking" rocks?

[EliNaut]

I was thinking. (Hell I always am.)

With the small buzz going about the probes we've sent out to small asteroids and other bodies... I was wondering, since many of these bodies are on paths that go beyond our solar system(some come back even), would it not be possible to either land a unit or perhaps tether to the surface (okay, we'd have to worry about collisions for that one, unless it could afford to keep its distance with thrusters), so we could send probes farther out? Just ride it out...



~EliNaut

 

[T.Neo]

I don't think so, as you would still use up that Dv to sync velocities with the rock. Otherwise... splat.

 

[Urwumpe]

What does it improve for the probe, to be tethered to a dead elephant?

 

[EliNaut]

I was thinking if we just outfit the landing probe, suggesting it can successfully land, with some kind of instrument(s) that would scan outward as the body moved along and see if there's anything we can see out there that we can't see from here. I don't know really - its just an idea. I don't know too much about the behavior of asteroids and what benefit it would do other than to (my guess) to save fuel in a journey across the solar system or beyond it.

 

[Quick_Nick]

Isn't a project like Deep Impact basically the idea here? (different goal, 'same' result) Of course, you want the satellite to survive the impact to have use later.

 

[Artlav]

Let's see if i got the idea right:

Given a hyperbolic asteroid and a probe, to send the probe from near-earth solar orbit to interstellar space using the asteroid.

The probe rendezvous with the asteroid, then there are 2 braking approaches i can think of.


Plan B is to use a series of huge disposable and not shock absorbers between the payload and the target asteroid, and slam the probe into it.

Considering the DV of 10 to 20 km/s, could it possibly be made survivable for a canonshot-grade equipment without using unobtanium too much?


Plan A is to have a probe with a long tether in it.
The tether is shot out of the probe and the hook is accelerated towards the asteroid, hooking itself on it, with the probe sliding down the tether, slowing down using either the railgun principle or the contact brakes.

Does it sound plausible?
Both lodging the hook and braking parts looks unmakeable...

 

[EliNaut]

Let's see if i got the idea right...

...Both lodging the hook and braking parts looks unmakeable...

Yes thats basically what I had in mind.
I like to think of someone on a skateboard tying a rope to a car and riding it down the street. :rofl:

The thing is, the suspended probe on the tether would have to have some kind of small thrusting system, so it wouldn't drift into the body. Or.. actually... give me a minute. Your drawing gave me another idea.

*PROCESSING... PLEASE WAIT................*

Okay, we have our unmanned vessel, comprised of two parts. The "bottom" will seperate, but still be connected to the upper body via tether. This lower half would slam into the rock, with the objective of being lodged in there(also being sure that the force won't scatter the body). Then, when its secure, the upper half, after stabilizing from the insertion, would reel itself in, using some sort of RCS to keep it stable, and re-attach with the lower half, like a bird flying into its nest.

EDIT: Better comparison - think of a grappling hook.

 

[T.Neo]

Okay, we have our unmanned vessel, comprised of two parts. The "bottom" will seperate, but still be connected to the upper body via tether. This lower half would slam into the rock, with the objective of being lodged in there(also being sure that the force won't scatter the body). Then, when its secure, the upper half, after stabilizing from the insertion, would reel itself in, using some sort of RCS to keep it stable, and re-attach with the lower half, like a bird flying into its nest.

But wouldn't it still go splat?

 

[EliNaut]

But wouldn't it still go splat?

Not if we make it out of a strong enough material. Plus it all depends on the relative speed, how big the body is, what its made out of etc etc. What I just said is basically the same thing as the drawing above, its just that the part the body is dragging gets reeled in to sit on the hook/tether root.

 

[Artlav]

I like to think of someone on a skateboard tying a rope to a car and riding it down the street.

Does not sound right. It's space we're talking about, so all the probe needs is the jolt, the presence of rope to the car is irrelevant after that.

This lower half would slam into the rock, with the objective of being lodged in there(also being sure that the force won't scatter the body). Then, when its secure, the upper half, after stabilizing from the insertion, would reel itself in, using some sort of RCS to keep it stable, and re-attach with the lower half, like a bird flying into its nest.

It slams and lodges. It might be a conceivable to make a tether that can survive a million G's without breaking or vaporising. After that there will be a probe sliding along the tether with relative velocity of a dozen km/s at the least, having only like 10 seconds to brake to asteroid speed. That is still a hell of a tether.

Why reel the probe in to the asteroid? Just use the RCS to get clear of it's gravity. Unless, the asteroid itself is the object of study, of course.

 

[T.Neo]

But won't you still need the same Dv to match velocities as if you didn't have the tether? :huh:

 

[Artlav]

But won't you still need the same Dv to match velocities as if you didn't have the tether? :huh:

I thought the whole point of that maneuver was to use the tether to match velocities.

 

[T.Neo]

I thought the whole point of that maneuver was to use the tether to match velocities.

I dunno. I think it would actually be easier to carry you're own propellant then to build a tether like that.

Or, what about using a slingshot around a gas giant and a correction burn (still pretty large) to rendezvous with the asteroid?

 

[Scarecrow]

Here's a possible solution to the splat problem for a large vessel. The only part of this that may or may not need to be unobtanium is the tether (or anchor line). I haven't attempted to calculate anything:

As a large vessel approaches the asteroid, it launches a small anchor ship with lots of DV and very elastic anchor line to go land on the asteroid, and attach itself firmly. As the asteroid and ship get farther apart, the anchor line begins to stretch, transferring momentum from the asteroid to the ship. Whenever you want, you command the anchor to let go, and reel it in again. Under ideal conditions (ie: the asteroid is headed straight at you, and you want to get lots of velocity in the direction it's going, relative to you), and with the asteroid much bigger than the ship, the ship/anchor combination should be able to accelerate by twice the asteroid's velocity relative to the ship for just the propellant cost of matching the anchor's velocity (and some of the anchor line) with the asteroid. Of course, if you want to go somewhere in particular, and not just "as fast as possible", then you won't get quite as much benefit from the interaction.

As with many things, this would be a cool addon.

 

[EliNaut]

Here's a possible solution to the splat problem for a large vessel. The only part of this that may or may not need to be unobtanium is the tether (or anchor line). I haven't attempted to calculate anything:

As a large vessel approaches the asteroid, it launches a small anchor ship with lots of DV and very elastic anchor line to go land on the asteroid, and attach itself firmly. As the asteroid and ship get farther apart, the anchor line begins to stretch, transferring momentum from the asteroid to the ship. Whenever you want, you command the anchor to let go, and reel it in again. Under ideal conditions (ie: the asteroid is headed straight at you, and you want to get lots of velocity in the direction it's going, relative to you), and with the asteroid much bigger than the ship, the ship/anchor combination should be able to accelerate by twice the asteroid's velocity relative to the ship for just the propellant cost of matching the anchor's velocity (and some of the anchor line) with the asteroid. Of course, if you want to go somewhere in particular, and not just "as fast as possible", then you won't get quite as much benefit from the interaction.

As with many things, this would be a cool addon.

Yes thats more or less what I was originally thinking. Though keep in mind, if the vessel being "tugged" is larger than the asteroid, then its speed would be affected too. Of course, this is going to happen with any size ship that you do this manuver with, but, if the vessel is too large you might actually end up tugging it.

Edit: Wait... nevermind, sorry. I misread that.

 

[Ark]

Seems to me like you'd have to expend the fuel to match the asteroid's orbit anyway, so you'd be better off just firing the probe in whatever trajectory you want, so you don't have to worry about landing/tethering or having your view obscured by the asteroid. The only other way would be to engineer a way to survive a VERY high-speed impact, which would be difficult and expensive.

 

[EliNaut]

Seems to me like you'd have to expend the fuel to match the asteroid's orbit anyway, so you'd be better off just firing the probe in whatever trajectory you want, so you don't have to worry about landing/tethering or having your view obscured by the asteroid. The only other way would be to engineer a way to survive a VERY high-speed impact, which would be difficult and expensive.

You've missed one of our points Ark.
We're also suggesting that this asteroid is on a trajectory that will go through our system and go beyond - so in a way, is this a large fuel saver, if we could manage to hop on this interstellar bus. And also that means we're not matching its orbit, rather intersecting its hyperbolic path.

 

[-Pv-]

I agree with those who propose the energy used to get within engineering limits of the bus is great enough there is little to gain from the bus. If the bus stopped at the light so the skate board could hook on, then fine. You also need a bus to go where you want to go which justifies the expense. Once you hook to the bus, then why limit yourself to that when for a very small additional expense, you leave the bus behind and forgo any additional risk the bus transfers to your ship. We have some nicely placed gravity wells which do a better job cheaper and we don't slow down the assist mech in the process.

In space no one can hear you scream "free!!!!"
-Pv-

 

[doggie015]

It slams and lodges. It might be a conceivable to make a tether that can survive a million G's without breaking or vaporising. After that there will be a probe sliding along the tether with relative velocity of a dozen km/s at the least, having only like 10 seconds to brake to asteroid speed. That is still a hell of a tether.

Why reel the probe in to the asteroid? Just use the RCS to get clear of it's gravity. Unless, the asteroid itself is the object of study, of course.

Here is my method: have a probe equilise velocity with the body you want to attach to with some movement towards the body. This movement is countered when a teather and hook attached to the probe via a LONG cable fire from the probe powered by either a large spring or air (remember we are dealing with a vacum outside the probe here). The teather hooks onto the body and the probe simply pulls itself it. Oh, and in case you are wondering; a spring WILL work as every action has an equil and opposite re-action. What do you think?

 

[EtherDragon]

Here is my method: have a probe equilise velocity with the body you want to attach to with some movement towards the body.

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.