Space Train

Gibbon · 2002-06-12 23:24:40

I've read snippets of info on the use of Solar Sailors and I was wondering if it would be possible to use one as a type of train. The idea is that you have a large sail with attached crew compartment. You could possibly have a rotating taurus to create gravity if the money or need was there.
The carriages on this would be loads from shuttles or rockets.
The advantage of this design is, the sails could have solar cells spread through them and, because the sails must be in sunlight, permanent power. It is also a reusable vehicle that could be stationed in Mars orbit acting as a space station. The fact that the vehicle requires no fuel means that is can carry larger payloads and can easily be slowed down which means that you won't have to wait for a launch window to head off for Mars.
I believe that the biggest drawback to a sailor is that it is rather slow compared to rockets (this is an assumption, comparing a yacht to a powerboat). If people could please reply with comments it would be appreciated as it could well prove to be a useful item in interplanetery travel.

Pat Galea · 2002-06-13 00:37:26

Solar sails are very interesting, but as you said, they have very low thrust. Total mission time would probably be totally unacceptable for the crew on board.

I think it's more likely that sails would find a use for transporting non-perishable supplies, e.g. tools, stable chemicals, etc. You don't really care how long it takes any individual ship to get there; you can just keep a stream of them going, and pick them up in Mars orbit.

Once unloaded, the guys at the Phobos depot can load the ship with Mars manufactures, and set it off on its way back to Earth.

Shaun Barrett · 2002-06-13 01:10:48

I've never bothered to look up the principles of solar sailing. Moving away from the sun seems self-explanatory but how do you sail sunwards?
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Gibbon · 2002-06-13 01:12:25

my actual plan was that the sail could be used transport the equipment to Mars orbit. If a rotating Taurus were implemented then when the whole thing arrives in Mars orbit, it could be used as a space station for people to get reconditioned to Earth gravity. I'm sure that it wouldn't be too hard to attach the station to a moon.

edit

Shaun, ever gone sailing in a boat? Sailing towards the sun would be similiar to sailing into the wind I guess. You would probably have to aim just off the sun and overshoot your course, or just aim VERY far in front of your target which would almost certainly be around the 45 degree mark, depending on the position of Earth etc. I don't think it would be all the hard to get back to Earth, just slower.

Shaun Barrett · 2002-06-13 03:19:36

I understand "tacking" into the wind in a yacht on Earth, but that uses the pressure of the water on the hull and the keel in such a way as to allow you to sail almost straight into the wind. (Well ... within, say, 30 degrees of straight into the wind, anyway.)
There's nothing for the ship to push against in interplanetary space, so tacking would be difficult, I think.
Obviously, there's a simple explanation or people like Sir Arthur C. Clarke wouldn't be so enthusiastic about it.
It's just that I can't quite get a handle on it and would appreciate an "idiot's guide to solar sailing"!!!

Gibbon · 2002-06-13 04:24:57

ha ha, as would I.
One possible means of returning could be to use the suns gravity to pull the ship back closer to the Earth. (I'm not sure about this but it would probably be, like the sail, slow).

I get the feeling that this thing would just be used to go to Mars orbit and stay there as a space station.

Pat Galea · 2002-06-13 12:35:00

This should be useful to you:
How Solar Sails Work

Aetius · 2002-06-16 06:19:24

I think solar sails are amazing, and the fact that the spacefaring nations have spent so little to develop them is sad. As mentioned by others, they would probably not be suitable for colonists, but they'd be perfect for cargo.

Getting people to Mars is only part of the equation. Without an economically feasible way to transport hundreds of tons of supplies to Mars during each launch opportunity, colonization will never get off the ground (no pun intended).

Aetius · 2002-06-16 06:22:53

Another cool site regarding solar sails:

Space Sailing

Phobos · 2002-06-16 12:16:52

Getting people to Mars is only part of the equation. Without an economically feasible way to transport hundreds of tons of supplies to Mars during each launch opportunity, colonization will never get off the ground (no pun intended).

I remember reading somewhere that a few near earth asteroids have convenient orbits that bring them in close proximity to both Earth and Mars. Maybe we could utilize these as cargo carriers between the two planets. You could pack a lot onto an asteroid. Byron mentioned the use of rail guns to blast payloads into orbit. I imagine if we just shot the payloads into space then used a tug to load them onto the asteroids we might save a lot of the expense of using conventional launch technology. Maybe we could put rail guns on the asteroids themselves to shoot the payloads into the orbit of the planet they're nearing. Probably not feasible, but who knows.

Tom Jolly · 2002-06-17 12:28:57

Actually, slowing down is pretty easy. As a baseline, imagine a solar sail in orbit around the sun, outside the influence of Earth. If the solar sail is perpendicular to the path of the solar wind, the whole force of the solar wind will be bent on pushing the sail away from the sun, and its orbit will slowly spiral outward. Now, tilt the solar sail at a steep angle relative to the sun. If you've tilted it the right way, the solar wind will provide a small vector pushing out, but a very large vector slowing down your orbit. Slower orbits spiral inward (assuming continuous thrust. A pulsed thrust would merely put you in an elliptical orbit).

Shaun Barrett · 2002-06-17 18:55:22

Oh yehhh! Of course. Simple really. Thanksalot Tom!!

dicktice · 2002-12-01 15:13:35

Solar (light) sailing: Forget the yacht analogy, which tacks by means of aerodynamic horizontal "lift" to sail windward. Solar sailing would use vectored photon thrust, either to accelerate orbital velocity to retreat from, or decelerate orbital velocity to approach, the Sun or whatever is being orbited. Of course, sailing with the Sun at your back would accelerate you away from the Sun faster than vectoring, and would permit "loitering" at any distance without orbiting the Sun, while eg. waiting for your destination of choice to arrive in your space. (Matching velocities and going into orbit arout it would be as difficult as navigating a tall ship into harbour without a tug, but isn't that what sailing skippers are for?) Sailing out of the plane of the ecliptic would be another great use for Solar sailing.
Solar (wind) sailing: The disadvantage of decreasing photon pressure with increasing distance from the Sun may not be too bad out to the Asteroid Belt. And I have read that the solar wind possibly can be used, instead of light pressure, by magnetizing the spacecraft and injecting hydrogen ions into the field, against which the solar-wind particles would impinge. I don't know if vector sailing would be possible, since the "surface" of the resulting ion bubble would resemble a cloud. But, the bubble apparently would expand with distance from the Sun in exact proportion with the decrease in Solar wind density, maintaining thrust constant to the outer planets. Pretty convenient, eh?

Shaun Barrett · 2002-12-01 19:02:54

Hi Dicktice!

This solar wind sailing, out past the asteroid belt, sounds like it might provide as much outward thrust as we'll need. Particularly if the 'bubble' expands in direct proportion to the reduction in solar wind density.
But the Sun's gravitational influence is declining as the square of the distance out.
Wouldn't this mean that, while outward bound journeys might be accomplished in reasonable time-frames, coming home again would take far longer?
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dicktice · 2002-12-03 13:56:18

Shaun, I never considered returning...I thought the whole idea was to get out there as cheaply and soon as possible, to do stuff, in the case of Jupiter-space, with robot devices. But beyond Mars-space, "asteroid miners" of the human variety may want to return from time to time. In that case, I assume solar sails would permit retro-orbital vectoring until they dropped directly sunward to the distance desired, and then vector into orbit again. I'm pretty sure, the advent of high efficiency, nuclear-powered ion thrusters will put solar sailors out of business (except sport) just as steam did the tall ships. (I read that somewhere, it sounds like Clarke in fact.) But, solar-wind driven craft are being suggested as the initial stellar probes, for the very reasons you brought up. Great to hobnob with you!

soph · 2002-12-03 18:24:04

why couldnt they be used together? maybe the sails could be deployed for turning or breaking, so that the thrusters wouldnt have to be used to break the ship or turn it, reducing the cost of missions, or the time, depending on whats more important. the sails would be completely reusable too.

but im sure people would want to return from time to time. nobody wants to be in a desolate place forever.

dicktice · 2002-12-04 18:32:47

Place doesn't have to be desolate, just settled and populated. By that time, nuclear ion-thrusters should be the norm, so time between planets, or whatever, tolerable.

ronondexfan · 2012-09-08 20:03:28

Shaun Barrett wrote:

I understand "tacking" into the wind in a yacht on Earth, but that uses the pressure of the water on the hull and the keel in such a way as to allow you to sail almost straight into the wind. (Well ... within, say, 30 degrees of straight into the wind, anyway.)
There's nothing for the ship to push against in interplanetary space, so tacking would be difficult, I think.

I recall reading somewhere the idea was to use a "magnetic keel" to "anchor" the ship to allow her to change direction. It occurs to me you might also change the attitude of the sail relative to the sun, to change the amount of "solation". (Is there a word for that?)

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