Swingin' on a Comet

A thought just occurred to me and I’m wondering about it…

Considering the great speed of Comets, would it be practical to design a ship that would hitch a ride on one and be towed away to some remote part of the solar system or can we do better with our own current propulsion systems?

If your ship has a propulsion system that will allow it to intercept (match speed and course with) a comet, then making a rendezvous with a comet won’t actually do you any good, unless you want to study comets up close. In other words, to tag along with a comet, you’d have to be going as faat and as far as a comet to start with.

Our deep space ships have repeatedly used gravity assist maneuvers, but I don’t think a comet would have a big enough gravity well to make that terribly worthwhile.

I wasn’t thinking matching speed, etc. I was thinking more along the lines of throwing a grappling hook (to use a metaphor) and tagging a ride as it passed by.

Drunk or stupid? You decide, people. :wally

Makes sense to me, but why a comet? Aren’t asteroids a lot better- you don’t get that tail of fly-off gas. And some of them have similar eccentricity in their orbits. You just don’t realize it, because they haven’t been recorded historically like comets, but when you investigate a single one, that’s what you often find.

This reminds me of an old Baron Munchausen story. During one of his military campaigns, he grabbed a cannonball just as it was fired off and rode it high into the air. But realizing that the shot would land him in the ememy camp, he grabbed another cannonball going the other way which brought him back.

I don’t know about Baron Munchausen, but I’ve got visions of Pecos Bill dancing in my head.

By any chance is your name Applewhite and do you want me to join a cult where I will have to look like everybody else above and below the belt?

I don’t care which comet you’re following, I’m staying here.

Yeesh! Enough of the flames! This isn’t the pit, guys! I don’t think I asked anything ridiculous. Look… picture this… A ship positions itself in the path of a comet or asteroid and then either fires some sort of harpoon-like object or throws a strong net-like device out to hit the comet as it goes by. The comet will then take the ship with it. I don’t see why this is such a crazy idea… however it may be impractical. I really don’t know how fast comets and asteroids can go and I’m not sure if we could garauntee the safety of the craft once it’s done this.

I think this is the problem: have you ever tried throwing a grappling hook and hitching a ride on an express train as it barrels by you on the tracks? Assuming you had the technology to grapple-hook a fast-moving asteroid or comet, the sudden dramatic acceleration would wreak havoc on you and your ship (just as you would have your arms wrenched off if you tried the express train trick).

I imagine that if you had a vehicle capable of matching the velocity and trajectory of a comet/asteroid, you could attempt to attach your craft to it and hitch a ride, thereby conserving fuel for the duration of the comet ride.

Sorry, Sorry, got carried away.

Seriously, the Russians came up with the roughly same idea for an unmanned probe not long before Hale Bop, at least I think it was Hale Bop. But they weren’t even going to use your grappling hook idea. They were going to manuver the vessel/probe in front of the comet and let the comet catch up and do all the work (much as MEBuckner outlined in his/her post and ended up facing the same questions).

Numerous problems intervened (not the least of which was it was the Russian space program attempting to do this on about a $12.95 budget) including labor problems, limited time and an insufficent delivery system. The thing figuratively and literally never got off the ground.

Before you pat yourself on the back for having similar ideas to the science types in Russia, however, it should be noted that this was the same program that suggested communicating with cosmonauts by ESP as opposed to using more mundane and costly communication techniques.

I’ve got in mind a scene from “Fandango” (spoiler)where Kevin Costner and his buddies’ car needs a tow, so they tie a rope to their front bumper and lasso a passing freight train. They await a sudden acceleration as the slack runs out on the rope. Then wham! Their bumper gets ripped off their car, and they’re still stuck. :D:D

Great movie! It’s even got “chick flick” stuff in it, and it’s only rated PG, so it’d be good for the whole family.

Design problem # 1 - find a cable/net strong enough not to snap (impossible?)

Design problem # 2 - find a way to connect the cable/net to the ship so that it doesn’t tear out (impossible?)

#3 - find a way to keep the ship from falling apart when suddenly accelerated by 50,000 mph in an instant*

#4 - if there’s a crew - keep them from being turned to mush when they hit the back wall

#5 - etc.

An interesting idea, but remember that comets/asteroids can be a few miles across & travelling at incredible speeds (near the Earth anyway). That’s a LOT of momentum to catch.

Oncle Bière made a good point about the comets coma & tail being a problem to get around/through.

The net seems impossible given the size of a comet/asteroid. The harpoon would have to be able to latch on well enough to pull a massive ship (not easy to sink a harpoon into rock or ice).

    • Of course, this assumes near-zero velocity compared to the comet/asteroid. I suppose you could have some closer relative velocity so it would be more of a velocity boost effect instead of a from-zero acceleration. But gravity assists (slingshots) by planets & moons seem more elegant & feasible.

If you were using a net, I’d be concerned also about the size of the comet–you’d need a net several miles square. Too bad that the comet isn’t so massive–a gravity assist off a fast-moving object would be that much better.

With a net OR a harpoon, I’d also worry about the mechanical strength of the comet. Comets are probably rubble piles–they’re composed of chunks of (very low-density, light-weight, “fluffy”) ice held together just by their own gravity. Pretty hard to get a good hold on 'em.

Oh, plus the acceleration problem. . .

Didn’t the Little Prince use a butterfly net to catch on to passing comets? :slight_smile:

Well, let’s consider that it was possible to hitch a ride on a comet. What would that buy you? It’s not like there are regularly scheduled comets to interesting places in the solar system. Yes, you could get an unmanned probe out on the Grand Tour of the solar system, but all comets really do is make really big, long, slow ellipses around the sun. From the standpoint of interstellar distances, comets don’t move all that fast. So you’d have to develop a lot of technology (i.e. really strong rope :slight_smile: ) that would get used very infrequently if at all and wouldn’t take you anywhere you wanted to go.

The problem is similar to bungee jumping (does anyone do that anymore?) you just don’t want to come a sudden stop/start. Or like reeling in a fish, perhaps. Let the line run out, while braking on the reel. Of course, you need a heck of long line.

Now, how do you hook on to what I thought was a giant mushy snowball?

Wasn’t it just a week or two ago that NASA successfully landed an explorer (not a lander) on an asteroid? What is the speed difference, if any, between an asteroid and a comet?

The reason why these ideas don’t work is that once you’ve matched velocity and trajectory with the comet or asteroid, there is no more “work” to do. Spaceships or comets either one are in unpowered ballistic trajectories–you don’t have to fire the engines continuously just to maintain a constant speed, the way ships or aircraft do, because there’s no friction (from the ocean or atmosphere) to overcome. Of course, a really advanced spaceship might have an engine capable of constant acceleration–but that would make your ship capable of attaining much greater speeds in a shorter period of time than it could ever hope to by mucking around with hitching rides on celestial bodies.

Now, in theory, I think that if a spaceship was just hanging around and it shot out a harpoon or a “tractor beam” or a big butterfly net and snagged on to a passing comet or asteroid it could in fact be accelerated and go zipping off through the Solar System. The main objections to this are probably practical, but are of such magnitude that I imagine they’ll be building a skyhook first.
[sub](I’m a guy, by the way.)[/sub]

Just a comment on skyhooks, by the way: Fullerene nanotubes have the requisite strength to weight ratio, and we already know how to make those. At his point, it’s mostly a matter of money preventing us from building a space elevator. Give it a few hundred years or so.