Solar Super-Sail Could Reach Mars in a Month

ti-coune sent us a story running on newscientist describing solar super sails and how they could one day get us to Mars in a month. The key is a special new paint. The cast of Trading Spaces is unavailable for comment.

Comments

And how does it slow down when its there?

[Viol8]

Or get back to earth for that matter? Nice idea as long as you don't mind a one way trip into deep space.

Re:And how does it slow down when its there?

[Angstroem]

Slow down: Rocket thrusters (mainly for maneuvering) and athmosphere.

Coming back: Send robotic missions do deliver necessary parts and prefabricated modules, then send human heroes to put everything together. If some part fails, they at least are heroes.

Mind you, exploration never included the guarantee of a safe way back. It always took some people to take the risk of losing their lives.

Because you can now safely travel over the Pacific Ocean in 5 hours doesn't mean it always was like that.

Why pipe microwaves from the surface?

[FreeUser]

From TFA:

Gregory Benford of the University of California, Irvine, and his brother James, who runs aerospace research firm Microwave Sciences in Lafayette, California, envisage beaming microwave energy up from Earth to boil off volatile molecules from a specially formulated paint applied to the sail. The recoil of the molecules as they streamed off the sail would give it a significant kick that would help the craft on its way.

Why does this seem incredibly wasteful of energy?

Wouldn't it be far wiser to build solar panels in orbit, use them to power Microwaves, and avoid the attenuation in the atmosphere? This would have the added advantage of not draining power from the Earth to power the spacecraft: we would get our power from the Sun and pipe it directly to the spacecraft as Microwaves, without involving the planet at all (except, of course, as controlling entity).

Re:Why pipe microwaves from the surface?

[Waffle Iron]

Why does this seem incredibly wasteful of energy?

Wouldn't it be far wiser to build solar panels in orbit, use them to power Microwaves, and avoid the attenuation in the atmosphere?

Talk about penny wise, pound foolish. A 60 MW solar power station in orbit would be far larger than the International Space Station. It cost dozens of $Billions just to launch the space station; designing, launching and maintaining a 60MW station would probably cost hundreds of $Billions.

When you spend money on something, you're allocating a certain fraction of the economy towards a that purpose. That comes with a roughly similar fraction of the world's energy consumption. Dedicating huge teams of people designing, building and launching an orbital power platform will consume a commensurate amount of energy down here on this planet as they go about their tasks. Building the station and the massive rockets to launch it will consume vast energy resources before it even gets off the ground; vastly more energy than the station could ever produce.

For example, assume the station costs $100 Billion. That's about 1% of one year of the ~$10 Trillion US economy. The US consumes about 1e20 joules of energy per year, so if the money spent on the station is associated with a proportional amount of energy, that's 1e18 joules. That's more power than a 60MW power plant would produce in 500 years.

Re:Fuel

[will_die]

Once you get it into inital orbit payload weight would not be a problem, size would matter size it could not block the sails. Whatever the payload is I hope that you don't mind it smashing into the planet. They don't discuss slowing down or landing.
Going at 60 kilometres per second it is going to take a good amount of fuel and time to slow that thing down.

Re:Cast? What cast?

[Catbeller]

Nope. I believe they said that it would require ONE hour of focused microwave energy on the sail while still in low earth orbit to achieve Ludicrous Speed.
Then it coasts.

So, basically you build 20 2 MW transmitters and focus their output on a point a few hundred or thousand miles away -- I assume after an hour the craft will be moving away pretty damned quick, so a few thousand miles then.

How does this thing STOP? You make Mars, but what's slowing it down from 150 miles per second so that it'll achieve orbit? Atmospheric braking? Um, no, let that go - no airbraking, it'd vaporize. Even if it could withstand a 150 mps entry without puffing out, it'd punch out of the atmosphere in seconds, with no time to kill much speed. No rockets either -- can't carry enough fuel to kill 150 mps.

You'd need another microwave array in a high Martian orbit to fire at the solar sail as it came streaking in from Earth, if you want it to downspeed to make orbit. I'd assume the sail reverses somehow, so the craft comes in tail first.

Now. If you want a FAST vehicle, build a solar powered multi-megawatt laser at an LaGrange point, and use the nicely focused red laser on a solar sail. The craft'll be at Mars in, what, two weeks?

There's a couple of points that occur to me: the mass of the object being towed by the sail is irrelevant, mostly; you could tow the Sears Tower if you want. You'd just have to fire the lasers/microwaves for a longer time. A laser/purely reflective sail would be used for really heavy objects, and the gas-outing microwave system for smaller payloads, because the amount of paint on the sail is limited and will be exhausted, while a pure mirror-sail is static and can be used indefinitely.