Elon got his rocket up ...

[Tom Ligon]

Dr. Bussard pretty much made this point to me regarding his idea of proper Mars transportation: to heck with Hohman ellipses, just point the rocket and go.

He had a taste for fast cars and fast rockets. I expect a strong Flash Gordon/Buck Rogers influence from his childhood. The discovery that no chemical rocket fuel would do this is why he invented nuclear rocketry.

If Elon Musk goes to Mars with a variant of the Falcon 9, it will be the slow way, milking orbits for everything they have to give.

As for "infinite impulse", I should note a trend. Looking at variable specific impulse rockets, as you raise specific impulse, you drop thrust. The ultimate is infinite specific impulse but no thrust, a rocket very efficient at doing nothing. The practical limit is to shine a light out the back and struggle to detect any acceleration at all. If you are in a gravity well in the inner system, forget these fantasies and work with actual systems.

[GIThruster]

Yes well, M-E thrusters always have the equivalent of an extremely high Isp. It's not really fair to make a straight comparison here because there's no propellant, but the point is if you build a craft that can lift from the Earth's gravity well, and provide constant thrust at that magnitude, then you have a "1 Gee Solution."

Bussard would have loved this. . .

Mars at its farthest approach to the Earth in 5 days, the asteroids in 6, Jupiter in 7 and Saturn and it's pretty moon Titan in just 9 days. Those are travel times comparable to the golden age of steamships, and certainly cheap and easy enough to colonize our planetary system.

[KitemanSA]

As for "infinite impulse", I should note a trend. Looking at variable specific impulse rockets, as you raise specific impulse, you drop thrust. The ultimate is infinite specific impulse but no thrust, a rocket very efficient at doing nothing. The practical limit is to shine a light out the back and struggle to detect any acceleration at all. If you are in a gravity well in the inner system, forget these fantasies and work with actual systems.

Tom, there are few time that I disagree with you but this is one. The trend you note may be true for "rockets" but not for light sails. Small thrust flux maybe, but very light weight (ok, mass already) so still useful.

Didn't JAXA just launch a light sail?

[AcesHigh]

Mars at its farthest approach to the Earth in 5 days, the asteroids in 6, Jupiter in 7 and Saturn and it's pretty moon Titan in just 9 days. Those are travel times comparable to the golden age of steamships, and certainly cheap and easy enough to colonize our planetary system.

better than sex...

[Tom Ligon]

We'll see how it goes ...

http://news.yahoo.com/s/space/20100618/ ... ndeepspace

I reserve judgement. For big interplanetary orbital maneuvers and very light payloads, I have no doubt solar sails can make a useful contribution. Their ability to get useful human missions to Mars is not so abundantly clear. A concentrated mass has to be connected to a huge and gossamer sail to make it work.

For hovering over the poles, I'd like to see the control system worked out. That's a delicate balancing act for a system that must respond quickly to changing conditions. Close in, a solar sail will respond to both photons and to solar wind, and the responses are not identical. A coronal mass ejection would probably cause havoc. The larger the sail is the harder it is going to be to "change tack". If you make it parachute-like, that means changing line lengths on multiple lines going to the comparatively massive payload. You think an old "army rag" parachute tended to swing wildly? Even worse would be a spinning disk membrane that had to be tilted on short notice.

[Skipjack]

I too have high hopes for March Woodward and co. I am sceptical but I do wish them all the best. It would change the world as we know it. Not just spaceships, but airplanes, flying cars, etc, etc.
But lets not get ahead of ourselves. We will see whether they can keep their promises. I give it a very small chance, but the consequences of success make me giggle...

[GIThruster]

Yes well, no one at Woodward and co have made any promises except to be honest and keep trying.

Jim is on vacation till the Fall. I doubt there will be any news from any of the projects until October os so.

[ltgbrown]

Not just spaceships, but airplanes, flying cars, etc, etc.

and lawnmowers!

If Dr. Woodward and co. can prove it true, it will equal (or surpass?) the wheel, fire and transitor. I am sKeptical also, but hopeful beyond words.

[Skipjack]

Jim is on vacation till the Fall. I doubt there will be any news from any of the projects until October os so.

Grrrr, waiting until fall = torture for somebody like me (yours truly is the personification of impatient).

[D Tibbets]

As for "infinite impulse", I should note a trend. Looking at variable specific impulse rockets, as you raise specific impulse, you drop thrust. The ultimate is infinite specific impulse but no thrust, a rocket very efficient at doing nothing. The practical limit is to shine a light out the back and struggle to detect any acceleration at all. If you are in a gravity well in the inner system, forget these fantasies and work with actual systems.

Tom, there are few time that I disagree with you but this is one. The trend you note may be true for "rockets" but not for light sails. Small thrust flux maybe, but very light weight (ok, mass already) so still useful.

Didn't JAXA just launch a light sail?

Light sails are only good for certain manovers in the inner solar system. Magnetic sails automatically increase is size as the solar flux decreases, so they will potentially work ~ equally well anywhere in the solar system.

If only it can be made to work...

http://en.wikipedia.org/wiki/Magnetic_sail

Dan Tibbets

[AcesHigh]

Jim is on vacation till the Fall. I doubt there will be any news from any of the projects until October os so.

Grrrr, waiting until fall = torture for somebody like me (yours truly is the personification of impatient).

imagine if we lived in the middle ages.

you would be lucky if you saw a SINGLE technological innovation in your whole life.

[AcesHigh]

Not just spaceships, but airplanes, flying cars, etc, etc.

and lawnmowers!

FIFA and Adidas will probably find a way to create an ME-Ball for the 2022 World Cup


ps: I guess most of you guys are americans and are not acquainted with the S.Africa World Cup ADIDAS´ Jaboulani(tm) ball controvery.

[kurt9]

Jim is on vacation till the Fall. I doubt there will be any news from any of the projects until October os so.

Grrrr, waiting until fall = torture for somebody like me (yours truly is the personification of impatient).

October eh? I was hoping they would demostrate their ME-2010 experiment by August. Oh well, whats two months?

Anyways, it will be interesting to see not only if the effect is real, but whether it works better using the dielectrics as thin-film lattice structure.

[Skipjack]

you would be lucky if you saw a SINGLE technological innovation in your whole life.

The torture!

[KitemanSA]

For hovering over the poles, I'd like to see the control system worked out. That's a delicate balancing act for a system that must respond quickly to changing conditions.

Well there is "hovering over the poles" and "hovering over the poles". What I was discussing was geo-synchronously orbiting the poles at high (but not 90degree) latitude. There was a different post about being in a 365.2XXXX day SOLAR orbit raised above an earth pole. Different issues and different control needs. To get to the same relative distance between satellite and Earth, I think the orbiting method provides a MUCH simpler solution. Maybe not.