[Janus]

Originally Posted by Gardamorg

Correction, in several years it can reach that speed,

After 9,513 years at the acceleration given in the quote.

Besides that, in order to get your ship up to 0.5c, still requires the equivalent of the the entire energy comsumption of the US for a year per metric ton of ship. And that is at 100% efficiency (which is not acheivable).

Your plan is just not feasable in many respects.

For one, Gleise's radial velocity towards the solar system is only 9 km/sec, which is not going to shave any real time of the trip. (For instance, at 0.5c for the ship speed, it would only shave about 40 seconds off of the trip time.)

[Gardamorg]

Originally Posted by Janus

After 9,513 years at the acceleration given in the quote.

Besides that, in order to get your ship up to 0.5c, still requires the equivalent of the the entire energy comsumption of the US for a year per metric ton of ship. And that is at 100% efficiency (which is not acheivable).

Your plan is just not feasable in many respects.

For one, Gleise's radial velocity towards the solar system is only 9 km/sec, which is not going to shave any real time of the trip. (For instance, at 0.5c for the ship speed, it would only shave about 40 seconds off of the trip time.)

My solar sail will be moving and accelerating many times faster than the solar sail designed in the quote, because the battery canons are following it at GREAT speeds, I'm not propusing using any more fuel than needed, if it doesn't reach half light speed it doesn't reach half light speed.

If your saying that any other propulsion would be faster or cheaper you are greatly mistaken, take Nuclear Pulse for example, quick jolts of speed doesn't equal a shorter flight there, the explosions that propel a craft aren't constant, therefore a craft that uses weaker yet constant propulsion will be moving in between each explosion of a nuclear pulse rocket, saving time.

Janus, it's the quickest/cheapest/best way to get there face it, there is no better way.

[C1ay]

Originally Posted by Gardamorg

Janus, it's the quickest/cheapest/best way to get there face it, there is no better way.

And you can prove this how?

[Moontanman]

Originally Posted by Gardamorg

My solar sail will be moving and accelerating many times faster than the solar sail designed in the quote, because the battery canons are following it at GREAT speeds, I'm not propusing using any more fuel than needed, if it doesn't reach half light speed it doesn't reach half light speed.

If your saying that any other propulsion would be faster or cheaper you are greatly mistaken, take Nuclear Pulse for example, quick jolts of speed doesn't equal a shorter flight there, the explosions that propel a craft aren't constant, therefore a craft that uses weaker yet constant propulsion will be moving in between each explosion of a nuclear pulse rocket, saving time.

Janus, it's the quickest/cheapest/best way to get there face it, there is no better way.

How do you get the laser cannons to follow your ship? Also what is the specific impulse of your set up? Manned or unmanned?

I postulate that a magnetic sail would be more efficient and able to accelerate even a huge mass to about .01 C given a large (nuclear) power source. The best thing about magnetic sails is they get bigger with no more power input as they get further from the sun, allowing the acceleration to be constant even though the power per square meter is always getting smaller as you get further from the sun.

[Janus]

Originally Posted by Gardamorg

My solar sail will be moving and accelerating many times faster than the solar sail designed in the quote, because the battery canons are following it at GREAT speeds, I'm not propusing using any more fuel than needed, if it doesn't reach half light speed it doesn't reach half light speed.

What GREAT speed is this? The speed you expect to get from the gravity slingshot just isn't there.
1. You can't continually gain speed by the way you show.
2. While you can pick up some speed by close flyby of planets, at best, you will gain a couple of km/sec above escape velocity from the Solar system. Meaning by the time you leave the Solar system you will only be moving at a couple of km/sec towards your target star. Meaning the rest of the speed of the craft will being from an increasing velocity difference between the cannons and the craft.
3. The cannons themselves won't even maintain the few km/sec they have. They will experience recoil from their own laser output, constantly slowing them down.

Your laser cannons would have to be huge. So huge, that the fuel needed to even get them into Solar orbit would be put to much better use just applied to the space craft proper and leaving the cannons on Earth. You don't gain anything by having the cannon "chasing" after the craft. You are actually robbing yourself of the best advantage of the light sail/laser cannon system; leaving the engine at home, where it has the resources of the planet to draw from to power it and keep it maintained.

You still haven't addressed the fact of the immense amounts of energy needed to get the craft up to any significant fraction of the speed of light.

To be quite frank, you simply have not displayed enough understanding of the basic orbital mechanics. engineering or physics involved.

[Gardamorg]

Originally Posted by Janus

What GREAT speed is this? The speed you expect to get from the gravity slingshot just isn't there.
1. You can't continually gain speed by the way you show.
2. While you can pick up some speed by close flyby of planets, at best, you will gain a couple of km/sec above escape velocity from the Solar system. Meaning by the time you leave the Solar system you will only be moving at a couple of km/sec towards your target star. Meaning the rest of the speed of the craft will being from an increasing velocity difference between the cannons and the craft.
3. The cannons themselves won't even maintain the few km/sec they have. They will experience recoil from their own laser output, constantly slowing them down.

Your laser cannons would have to be huge. So huge, that the fuel needed to even get them into Solar orbit would be put to much better use just applied to the space craft proper and leaving the cannons on Earth. You don't gain anything by having the cannon "chasing" after the craft. You are actually robbing yourself of the best advantage of the light sail/laser cannon system; leaving the engine at home, where it has the resources of the planet to draw from to power it and keep it maintained.

You still haven't addressed the fact of the immense amounts of energy needed to get the craft up to any significant fraction of the speed of light.

To be quite frank, you simply have not displayed enough understanding of the basic orbital mechanics. engineering or physics involved.

Let me make sure you understand,

Stage 3: The Craft uses the earth's gravity as a sling shot to get to the sun, and then orbits around the sun several times, each time orbiting to a further distance to immitate a super sling shot

Just putting that out there.

Your laser cannons would have to be huge. So huge, that the fuel needed to even get them into Solar orbit would be put to much better use just applied to the space craft proper and leaving the cannons on Earth.

Leaving the canons on Earth is so stupid, the Solar Sail would stop moving after a certain range, if the Baterry Canons were following the sail then it would stay in range to push it, and the Baterry Canons might slow the Craft down, but the Ion Boosters still provide greater thrust than the recoil of Battery Canons.

You still haven't addressed the fact of the immense amounts of energy needed to get the craft up to any significant fraction of the speed of light.

Yeah I did, the fact that the battery canons stay in range long enough for the sail to accelerate to a fraction.

Even if the two canons went closer to each other, on Earth, they would still lose range after a long period of time.

[CraigD]

Unfortunately, Gardamorg, the criticism made by Janus and others in this thread are, I think, right on: you must, at least approximately, work out the numbers for your design, not just sketch it (including the word “super” as many labels as you can ) and imagine it will perform as you hope. When you do, you’ll no doubt discover not only some fundamental problems involving mass and power, but upon attempting to adjust the design to overcome them, why “rocket science” is a common synonym for “a difficult task”, and why “the cold equations” are a famous literary metaphor for the unforgiving nature of spaceflight mechanics.

On the positive side, the idea of artificially powered light sails is widely considered one of the most promising approaches for spacecraft capable of reaching an extrasolar star withing a human lifetime. The main main advantages of this approach include (most of which Janus mentioned)

• that the propulsion power system (a gigantic, precisely focused laser, typically closely orbiting the sun) can be made as massive as needed, without affecting the acceleration of the low-mass lightsail spacecraft if propels
• and kept near our best (and, for all intents, only really big) available power source (the sun)
• and near all the maintenance and support people and materials it will need.

The main disadvantages include

• that even the most well-collimated lasers beams dissipate (become less powerful) with increased range, so the gigantic laser must be really gigantic,
• Light sails are very energy inefficient compared to mechanical motors and reaction-mass rockets, so the gigantic laser must be really, really gigantic,
• that, because the laser beam must be as narrow as possible to minimize power dissipation, keeping it on the distant spacecraft requires that it be really precise, many times more than the most precise existing aiming systems, such as those on space telescopes.

There are many variations on the “big propulsion system stays at home, little propelled craft goes on the trip” design theme, some of the most promising ones addressing the “light sails are very inefficient” issue by replacing the laser beam with a stream of bullet-like projectiles - which, if each is given a guidance and small course-correction propulsion system, can address the “must be really precisely aimed” issue.

Some of the best serious speculation on powered lightsail spacecraft were published by the late Robert Forward, who holds several patents on their technology. His 1985 hard science fiction novel “Rocheworld” has an excellent description of such a manned spacecraft the Prometheus, including illustrations and specifications in the book’s appendixes. The fictional Prometheus accelerated to .2 c in 20 years, coasted about 20 years, then used it’s separable multi-part sail to decelerate in about 2 years to rendezvous with planets in the Barnard's Star system, about 6 light-years from earth.

We’ve discussed powered lightsails several times in these forums, such as in this 5/1/2007 post, which has a few numbers on the aiming problem.

[Janus]

Originally Posted by Gardamorg

Let me make sure you understand,

Just putting that out there.

I repeat, Gravity slingshots don't work like that. Just orbiting the sun several times will not give you any extra velocity. Secondly the velocity you can gain from an actually gravity slingshot is limited

To just a bit over what you need to escape the Solar system, and most of that will be used up leaving the Solar system.

All you are doing by pursuing this argument is displaying your ignorance on the mechanism of gravity slingshots.

So now you going to have Ion boosters propelling the Laser cannon, which are going to be much more massive than the ship itself?
if you had Ion egines efficient enough to keep the massive cannon "in range", they would be efficent enough to propel the craft directly. But since Ion engines aren't efficient enough to get the ship up to even a fraction of the speed of light, neither are they going to be efficient enough to keep the more massive cannon "in range" for any significant length of time, especially since they will be fighting against the recoil of the lasers.

Yeah I did, the fact that the battery canons stay in range long enough for the sail to accelerate to a fraction.

[/quote]
No, you haven't. This has nothing to do with the energy it takes to accelerate an object up to a fraction of light speed. That is determined by the formula:
E = mc^2 (1/sqrt{1-{v^2}/{c^2}}-1 )

where v is the velocity you wish to reach. This is the bare minumum you need, no matter how you supply it. All fiddling around with the efficiency does is determine how much more energy you need to provide in order to achieve your goal.

[nkt]

Originally Posted by Gardamorg

Stage One: The craft will use Nuclear Pulse to propel it out of Earth's orbit.

I'm amazed no-one picked up on the issues of Stage 1. A launch from Florida would seem to be unlikely.

[Pyrotex]

Originally Posted by Gardamorg

The solar sail would be moving at over half the speed of light, now this trip might not be fast, over 20 years, maybe over 40, but it's still under 100, which is why this is our best alternative, and the quickest way to get there.

Gardamorg...

...fantastic!! I love your imagination. I love your drawings. I love your audacity.

You're gonna be a fine rocket scientist some day -- if these other yahoos don't squash you first.

I used to dream the same dreams 50 years ago! I drew rocket ships out my ass. I only dreamed of going to Mars. YOU are dreaming of going to the stars. You have the basic concepts: nuclear impulse, ion drive, solar sails (enhanced with solar cannons). I am totally impressed.

The importance of whether or not your idea will WORK -- as you have described it so far -- is not that important. Some rework is obviously necessary to "fine-tune" the trajectories and the techniques. What IS important is that you are beginning to UNDERSTAND the trajectories and techniques. You're developing the vocabulary. You're developing the concepts.

Pretty soon, you'll have mastered the math so you can actually calculate what size nuclear impulse you'll need, and how big that solar sail has to be, and how long will it really take to get to Gliese. And what to <<DO>> when you get to Gliese. Then,...

...then you will be unstoppable.

I love it.

I love it.

Pyro [NASA Rocket Scientist] [no kidding]