Space yacht will be first craft to travel on 'solar waves' as it sets sail for Venus

Daily Mail ^ | April 29, 2010 | Clair Bates

[C19fan]

A 'space yacht' propelled only by sunlight particles bouncing off its kite-shaped sails is to launch next month. A rocket carrying the Japanese craft will blast off from Tanegashima Space Center on May 18. Once in space the short cylindrical pod will separate from the rocket spinning up to 20 times a minute. This will help it to unfold its flexible 46ft sail, which is thinner than a human hair.

[a fool in paradise]

[Arthur Wildfire! March]

“Nobody has explained to me how a spacecraft can “tack” into the solar wind when it doesn’t have a keel.”

Good point. You need a keel so far as I know. I assumed they worked that out.

Otherwise, it will be a “Space Junk”.

[GonzoGOP]

Nobody has explained to me how a spacecraft can "tack" into the solar wind when it doesn't have a keel. The only momentum the Sun can add to the craft is a vector directly away from the Sun, no matter what angle the solar sail is pointed in.

But you do have a keel, the sun's gravity. The sun is always trying to pull you towards it. You speed forces you into an orbit. By changing the angle of the sail to the sun you can either increase or decrease your orbital velocity. If you decrease your velocity you will spiral inwards until you match orbit with Venus. Then you tack by changing the angle to the sun so that the solar rays cause you to increase orbital verbosity and you head back out towards Earth.

[GonzoGOP]

orbital verbosity

Orbital Velocity. I need to proof read after hitting spell check.

[Yo-Yo]

Yes, you have gravity. That pulls you on a vector directly towards the Sun. Yes you have a sail. That pushes you on a vector directly away from the Sun, no matter how the sail is angled. Assuming that you start from Earth, you also have an momentum at a right angle to the Sun.

I've read web sites that claim if you angle the sail, the sunlight will bounce off of the sail like a ricocheting bullet, and you will get a force vector that is the normal vector of incoming and outgoing rays. If you angle the sail properly, this resulting vector will impart a momentum that will slow your angular momemtum.

This is necessary to slow your orbital velocity so you can spiral in towards the Sun. I say that the sail will absorb more photons than it can reflect, and get a directly outward push.

Have you ever seen a radiometer? Which way do the vanes spin? They spin with the white faces leading, and the black faces trailing. That is because you get more momentum absorbing the light than you get reflecting the light.

[GonzoGOP]

This is necessary to slow your orbital velocity so you can spiral in towards the Sun. I say that the sail will absorb more photons than it can reflect, and get a directly outward push.

Except that the push directly away from the sun will be completely swamped by the sun's gravity. Just like the keel absorbs the tendency of the boat to move in the same direction as the wind. If you grab the back bumper of a car that in in neutral and pull up with 70% of your force and push forward with 30% of your force which way is the car going to go. Well since you lifting isn't nearly enough to overcome Earth's gravity the upwards force is completely canceled out. But since the car can move freely forward the much smaller amount of forward force does produce a forward movement. Or put another way you can pull a loaded coal barge by hand, not very fast, but it will move because there is virtually no friction and you are not fighting gravity. But you have no impact what so ever if you were to try to lift it.

[Yo-Yo]

Whether the solar wind force can overcome the Sun's pull is purely a matter of sail area vs. craft mass. The lower the mass, the more velocity a given amount of light pressure thrust will impart on the craft. The larger the sail area, the more thrust is imparted to the craft.

And there is more than just light at play here. There are other particles in the Solar Wind that would impart much more energy to a solar sail than just a photon would.

[SunkenCiv]

...propelled only by sunlight particles bouncing off its kite-shaped sails is to launch next month. A rocket carrying the Japanese craft...

Bravo for life's little ironies. :')

[KevinDavis]

Boring.. I want FTL!!!



For other space news go to: http://www.spacetoday.net
For a list of Private Space Companies: http://en.wikipedia.org/wiki/List_of_private_spaceflight_companies

[GeronL]

Did you see the video of the NASA FAIL in Australia with the balloon??

[GeronL]

Where is my warp engines?

[Delta Dawn]

How does one tie off in space?

[ErnBatavia]

one of the worst things that you will hear the doctor say is, “Sir, the disease that you have is nothing to ‘clap’ about.”

Our USMC Drill Instructors were a bit more concise on the first day of Boot Camp, when we had our "Pecker Check"....

"Awright, maggots! Drop your drawers and skin it back and milk it down!"

[Hot Tabasco]

Is this the first real attempt at a solar sail craft?

I'm thinking there was a mis-translation of the instructions that were provided following their application to enter the next America's Cup race.......

[Delta 21]

SPACE WEATHER
Current conditions
Solar wind
speed: 372.8 km/sec
density: 2.7 protons/cm3

Secure for heavy rolls!

[colorado tanker]

If you go to Venus, can you get a Venereal disease?

Not likely - the inhabitants are not friendly.

[happinesswithoutpeace]

/

[Impy]

Scientologist Kirsie Alley will want to go.

Cause she’d weigh less on Venus.

Al Gore will want to go to, to protest greenhouse gases.

[Vaquero]

Venus is between us and the sun. Which solar rays are they talking about harnessing here ?

like a sail boat, think ‘Tacking’.

in tacking you get the most speed when you are 90° from the wind...

the wind is the sun

you aim for where the target will be, not is. as Venus is directly inboard only for short periods, you (almost)parallel the earths orbit and move inward at the same time.

[wastedyears]

Just hope this captain isn't in charge of it.