The Sunjammer Project

a reply to: Kashai

What's really great about Mars and the Moon and asteroids is that they are a whole lot closer than even the nearest star.

Utilization does not imply exploitation. Iron oxide is not particularly valuable for either. It's rust.

Spending 30 years researching Alpha Centauri and related to a 20 year trip there and back with current technology, at least for me would be worth it.

a reply to: Kashai

We haven't even brought anything back from Mars, much less a one way probe to another star.

a reply to: Phage

And therein is what lies beneath. That being the iron that that has not oxidized and while Mars is one issue while the asteroid belt is another.



Ok so its kinda lame but it does, address the gist.

a reply to: Kashai

Yeah. Asteroids are cool.
I said that.

a reply to: Phage

I need to call it a night but wanted you to know that I really enjoyed our conversation.

Phage is correct. Slowing down is actually a problem.

You can not simply carry some ion/nuclear thruster plus fuel, as this would mean a lot of extra weight. Soar sail thrust is extremely low. Keeping it light is crucial to get anywhere in time.

One approach that I've read about would be to use the sail to slow down the payload. The sail is the heaviest part of the system, with the payload making a few percent of the total mass. So the idea is to separate the sail, and use it as a reflector to push away and slow down the payload by focusing the reflected light on it.

You'll still need an additional thruster for the final approach, when the sail has accelerated away, but it can be much lighter and smaller.

EDIT:
One idea that I think could work too, at least for non biological payloads, is to push away the payload from the sail forcefully, shoot it away using a rail gun like setup maybe.

a reply to: moebius

you could get over the weight problem with assembling your craft in orbit using many heavy lift rockets, and having drones waiting in orbit or on the ground on mars waiting for you.

MR/dr.Dyson had some pretty interesting ideas, no reason it wouldn't work, that is barring any launch failures.

originally posted by: Phage
a reply to: Kashai

Space is not easy.

But oh so necessary.

Couldn't have said it better.

More on it
www.nasa.gov...

a reply to: moebius

How to slow down a Solar Sail.

If you're asking about interstellar travel, then the answer is pretty simple; For diffuse, unfocused sources of light like the one emitted by stars, photon flux density decreases with the inverse square of the distance to its source, and with it photon pressure (imparted momentum of absorbed or, better yet, reflected photons) on the sail. So you accelerate away from the Solar system on photon pressure of the Sun, and decelerate on photon pressure of the destination star as you get closer to it. That might involve rotating the whole sail the other way around at half point, but that's it.

For more local orbits though, things get a bit more interesting. One thing we need to consider is that wherever in the Solar system we are, we're already in orbit around something. We're always orbiting some gravity well. And to move from one orbital altitude to another, say, decreasing heliocentric orbital altitude from one of the Earth (average of 1 AU) to one of Venus (about 0.7 AU), or increasing it to one of Mars (1.5 AU) and so on, we have to either increase angular momentum to move into a higher one, or decrease it to move into a lower one. So you don't really require the sail to be accelerating directly towards the Sun to decrease your orbital altitude with respect to it. It's enough to slow your orbital speed and with it decrease your angular momentum, and the orbit will progressively shrink to a lower altitude one.

space.stackexchange.com...

It would make sense that it would have a way to slow down.

a reply to: Phage


is it really possible that members of this forum actually do not read the data before responding and then run searches with regard to answers?

Fairly certain that you would have done same unless you already understood the response was to either run a rather very simple search.

That is to you.
***********************
Members, using the words, Above Top Secret, would, in general, attract individuals, who actually handled stuff like that.

Especially if back when win95 came out and someone like that was running searches using Bolian terms.

Here all of you are being offered the opportunity to actually and essentially, run a search upon "How do you slow down as solar sail".

And what?

This is the Science and Technology Forum which is a sub-forum of Above Top Secret. com.

Science is about an investigation using the resources available.

Thoughts?

a reply to: Kashai

Here all of you are being offered the opportunity to actually and essentially, run a search upon "How do you slow down as solar sail".

Yes, flipping the vessel around is an obvious solution. Now, think about how long it will take to slow down from interstellar velocities to interplanetary velocities and review this post:
www.abovetopsecret.com...

Oh, and by the way, it is possible we at this very moment are using technology like this in general.

a reply to: Phage

So in one is slowing as a result of an interstellar voyage, with respect to time?

As has been already offered an interstellar voyage, with this technology. to the nearest star would take about a decade.

Or at the time were you too busy to look into it as you were too, busy to run a search on "How to slow down a solar sail?"

Ok, so the word moron comes to mind and in general to any individual on the Internet who I conversed with on the Internet, that did not comprehend something as obvious as that.

Alternatively, implied is that you are FOS, IMHO.

a reply to: Kashai

Or at the time were you too busy to look into it as you were too, busy to run a search on "How to slow down a solar sail?"

No. I said that slowing down is a problem. Flipping the sail around does not change that. Using an ion drive does not change that.

Ok, so the word moron comes to mind

Thanks, and goodbye.

a reply to: Phage

Prove it or do you wish your position to be based on laurels????

To be clear you asked a stupid question, obviously.

I was wondering about slowing down too. What about laser-induced reverse thrust? Is that a possibility?

The thread on this forum discusses slowing down:


arstechnica.com...

a reply to: Phantom423

Deceleration of High-Velocity Interstellar Photon Sails into Bound Orbits at α Centauri Using Photogravitational Assists

1 Max Planck Institute for Solar System Research, PLATO Data Center, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany, heller@mps.mpg.de 2 Luiter Straße 21b, 47506 Neukirchen-Vluyn, Germany 3 Unidad Mixta Internacional Franco-Chilena de Astronomía, CNRS/INSU UMI 3386 and Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile 4 LESIA (UMR 8109), Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité, 5 Place Jules Janssen, 92195 Meudon, France

www.hou.usra.edu...

a reply to: Phantom423

The only real problem with solar sail technology is that if we encounter an object that is large enough to affects the spacecraft system and we do not have a contingency for addressing. that problem.

The rest involve simulations that take into consideration, the potential of influence from Dark Matter and Energy.

That really is irrelevant to a spacecraft of such a size.