New at Reason

Tim Cavanaugh | June 21, 2005

Who gives a fo'c'sle about the solar sail? What downhomey megaretailer has been seen squiring the brightest luminaries of la haute société? Who watches the credit card watchmen? Only Reason Express readers know for sure.

Comments

|6.21.05 @ 4:30PM|#

I'm really excited to see Cosmos 1. Although it's unlikely that a sailship will ever be suited for deep space exploration, if successful it could certainly bring down the cost of trips to the moon...please.

CodeMonkeySteve|6.21.05 @ 4:53PM|#

"Although it's unlikely that a sailship will ever be suited for deep space exploration, if successful it could certainly bring down the cost of trips to the moon."

I disagree. Solar sails are one of only two theoretical propulsion methods (that I know of) that don't carry their own fuel, and are therefore suitable for deep-space travel (the other being the Bussard ramjet).

The hardest part about getting to the moon is just getting out of Earth's gravity well, and the best solution to that is the space elevator. That will not only get you off the ground, but centrifugal force can throw you into a higher orbit suitable for reaching the moon and perhaps some nearby planets. For that matter, once you get on Luna, you get cheap solar energy to power a linear accelerator and launch you to pretty much anywhere you want to go in the Solar system.

Mike|6.21.05 @ 5:06PM|#

Perhaps if consumers demanded that any and all records they generate be encrypted from their creation until the records date-certain destruction, the entire financial system would be much more secure.

Except that the major data losses of the last few months have happened within companies that, presumably, would be doing the encryption and decryption.

The only way to secure the data is to make sure credit card companies, banks, and processors are all financially liable for fraud only they can protect against.

|6.21.05 @ 5:09PM|#

The problem with sailships is not going out, it's coming back in. Plus, the farther out you go the more your acceleration decreases. While there are theories about building lasers and whatnot, I don't view them as very practical.

I'm all for the space elevator, but I haven't heard any updates for nearly two years now, not that I've been keeping too a close watch on it.

|6.21.05 @ 5:29PM|#

While probably not a solution for deep space exploration, couldn't solar sails be used by ships just tooling around the upper atmosphere?

A lot like tugboats and dingys at a harbor?

|6.21.05 @ 5:43PM|#

I don't see the one-way nature of solar sails as a problem. They'd be great for sending a probe to a nearby star.

The problem is that once the probe gets there, the star will push the sails away.

So it comes down to a question of how much braking the star will exert, what kind of orbit it will get into, etc. We could send a probe with fuel on-board to navigate around the stellar system, but we have to have confidence in the parts working once it gets there. That's a long voyage and there's a lot of dust between here and there.

|6.21.05 @ 5:45PM|#

From what I've read, these aren't things that work in an atmosphere.

I can see using them to go outward, but how can you move towards the sun? Doesn't the solar wind blow out in a sphere?

I know sailing ships can tack against the wind, but they need to be a few point off the direction of the wind.

|6.21.05 @ 5:56PM|#

Actually, looking at the picture in USA Today shows it's in triangular parts, so some could be deployed perpendicular to the solar wind while others are parallel, so you could steer and I guess tack towards the sun.

Cool!

|6.21.05 @ 6:22PM|#

Actually, you can use sails to navigate closer to a central star, if you are in an orbit.

Essentially, you direct your sail to deflect the radiation ahead of you in your orbit.

This will slow you down (it will also tend to lift you into a higher orbit but the loss of velocity should dominate). Once your speed is sufficiently below that required to maintain a circular orbit (the push outward must also be counteracted), your ship's distance from the central star will begin to fall.

It should also be quite possible to change the plane of your orbit.

This is not tacking. Tacking depends on water resistance minimizing the sideways motion of a sailboat. In space the gas density is low enough that, for all intents and purposes, there is no such medium. So no tacking.

However, the momentum imparted from solar sails is very small, so travel times will be significant. The primary benefits will be realized when attempting to travel large distances within the Solar System, wherein the sails have time to impart large velocities.

I think once people build launchers out of linear accelerators on airless bodies throughout the solar system, this technology will go away. A network of linear accelerators is far more economical.

|6.21.05 @ 6:24PM|#

While probably not a solution for deep space exploration, couldn't solar sails be used by ships just tooling around the upper atmosphere?

A lot like tugboats and dingys at a harbor?

Comment by: mediageek at June 21, 2005 05:29 PM

These are for use above the atmosphere. Another thing you can do is use the solar wind to suspend a satellite in one position with respect to the Earth and Sun without using fuel.

|6.21.05 @ 6:36PM|#

Solar sailing is OK for your interplanetary yacht, or sending a deep space probe out that you don't need returned, but if you really want to move mass from orbit into space, an Orion drive or one of its variants is the way to go, at least until we can build some Bussard ramjets.

Some of these exotic beasties rely on lasers, so we might have some work for Doc Thoreau. He could rename himself Doctor Future, and really be the the archenemy of yesteryear!

Kevin

|6.21.05 @ 8:27PM|#

Really, the only way to truly travel throughout space is to go back in time an kill Einstein before he comes up with that pesky speed of light.

|6.21.05 @ 9:20PM|#

Thanks tarran!

|6.22.05 @ 1:24AM|#

Thanks tarran for clearing up one of the most comon misconceptions about space travel. Ships thrust to increase or decrease their orbital velocity. rarely will they actually thrust toward or away from the sun.

Another misunderstanding when it comes to solar sails is the use of the term "solar wind." Comonly this refers to the physical wind of ionized particles flowing away from the sun. But a solar sail does not use any kind of physical wind. Rather the "solar winnd" refered to in connection with solar sails is light itself. Radiation imparts a presure do to its change in momentum when reflected off a serfice (even though light is massles it still posesses momentum in acordance with general relativity) and this light pressure is what a solar sail uses to accelerate.

|6.22.05 @ 2:31AM|#

However, there is a proposed method to use the atual "solar wind" for space travel: the magsail.

|6.22.05 @ 9:56AM|#

http://www.space.com/missionlaunches/ap_solarsail_fail_050622.html

Seems like the solar sail didn't get into orbit, maybe the russians replaced the denatured alcohol as was mentioned in another thread?

|6.22.05 @ 1:22PM|#

The advantages of a solar sail are that sunlight is free and always On. The disadvantages are that the solar sail must remain highly reflective during its lifetime to work properly (which for now is unlikely) and any solar wind or interstellar dust could render it useless. Beyond Pluto is the Kuiper belt, and it is unlikely a solar sail could transverse this region of dust and planetoids unscathed. In any event, at some point the acceleration due to the Sun photons won't be able to overcome the ram pressure of interstellar gas and dust.
A Moon-based linear accelerator (read Heinlein's "The Moon is a Harsh Mistress") is a very efficient way to launch payloads into interplanetary space, maybe deep space, too. It could also launch globs of fuel for in-flight refueling, even filling the space lanes with local fuel dumps.
For that matter, an Earth-based linear accelerator could be of substantial benefit.
Too bad the Cosmos 1 launch failed; it would have been an interesting test of the technology.

|6.22.05 @ 5:09PM|#

I am intrigued by Mini-Magnetospheric Plasma Propulsion (M2P2). It creates a big magnetic field around the spacecraft, and then the craft is blown around by the solar wind (here meaning the outflux of charged particles from the sun, not the photon pressure of sunlight). Unlike the solar sail or the magsail, it doesn't require a large, fragile, and heavy (it all adds up) physical structure.

Info here