Thread: Space Accelerator

http://www.freewebs.com/rockypeterso...ccelerator.htm

I'm only a plumber who had this idea sitting on my toilet while I was drunk about an hour ago, so forgive me if it's stupid. I was just wondering if it would work, given that the materials required for building something like this were plausibly obtainable. I was thinking it could be a "pit stop" on the way to the moon or other space destinations, the word "stop" being used loosely as it's actually a device for speeding up an object in space. (If I'm not mistaken, when concerning physics, the word "acceleration" generally applies to objects that are moving, but not necessarily speeding up, right?)

I was wondering if something like this could be designed in space, far enough and not massive enough to affect Earth's gravity, but substantial enough to speed up a spacecraft.

Your accelerator would have to be massive to have any effect on a spacecraft. It would need to be the size of a moon or made of something incredibly dense like neutronium.

A much simpler solution would be to tether your spacecraft to a spinning object and transfer it's momentum directly without the use of a force as weak as gravity.

You mean spinn the moon and stick some diamond edged spiderweb string to it? :?

Moved to pseudoscience. No offense, but that's where this speculation belongs I think. Since it appears to fit the category of pseudoscience.

Either way, this idea isn't very plausible. At all. Also, for acceleration, we already use the planets.

I am offended that you moved my post. I don't know who you are and merely saying it isn't plausible doesn't convince me you have the authority to move it from the forum I chose. I'm looking for people who are interested in physics, not pseudoscience, and the science forum I used to go to was more helpful when discussing my ideas because they would explain why something wouldn't work and then have some fun helping me try to make it work.

It's not so much intended to be a speculation, but as a fun physics problem to exercise the imagination. I know we already use the planets and I know gravity can be a relatively weak force, but I feel my question would be better answered by people who are visiting the physics thread, like DarcgreY, instead of people who are predisposed to visit the pseudoscience thread.

Look, I know this thing isn't practical given our current resources, but that wasn't the point. I was wondering if it was theoretically possible. I was trying to make it a little more than pseudoscience, which is why I don't think it belongs in this thread. This is just draft one.

My imagined best case scenario was being able to place the accelerator at a distance from Earth where it could capture and propel a spacecraft from the edge of the atmosphere. Rocket fuel is expensive, but if a specially designed airplane could fly high enough to be grabbed by the accelerator's force it'd save a bunch of money and make space travel more feasible.

Originally Posted by GrantG

I am offended that you moved my post. I don't know who you are and merely saying it isn't plausible doesn't convince me you have the authority to move it from the forum I chose. I'm looking for people who are interested in physics, not pseudoscience, and the science forum I used to go to was more helpful when discussing my ideas because they would explain why something wouldn't work and then have some fun helping me try to make it work.

You misunderstand the move. pseudoscience discusses all matters, including physics. If we had a physics-pseudoscience, I'd have moved it there. Then again, maybe it's under the class of experimental physics...I'll ask another moderator.

And as a moderator we move posts to better suite a reader and posters interests. Technically, from what I can tell, this IS under the category of pseudoscience physics.

It's not so much intended to be a speculation, but as a fun physics problem to exercise the imagination. I know we already use the planets and I know gravity can be a relatively weak force, but I feel my question would be better answered by people who are visiting the physics thread, like DarcgreY, instead of people who are predisposed to visit the pseudoscience thread.

I'm quite sure they'll find it anyway. Many people just click the "posts made since you last signed in" thing, they'll see it anyway.

Look, I know this thing isn't practical given our current resources, but that wasn't the point. I was wondering if it was theoretically possible. I was trying to make it a little more than pseudoscience, which is why I don't think it belongs in this thread. This is just draft one.

Theoretically, if you have anything with enough density and mass, yes it's possible.

My imagined best case scenario was being able to place the accelerator at a distance from Earth where it could capture and propel a spacecraft from the edge of the atmosphere. Rocket fuel is expensive, but if a specially designed airplane could fly high enough to be grabbed by the accelerator's force it'd save a bunch of money and make space travel more feasible.

Would it fuck up the planets/moons? Yes.

Yeah, it was wrong to move it to Psuedo science, - that should be for hollywood stuff - It all looks feasible - it's just not cost effective though - I could not get the pictures but from the words and your original post I think I see what you are getting at, acceleration is the rate of change of velocity of a mass so if your ship is at a constant speed it is neother accelerating nor decelerating. Just a plumber? - a noble profesion indeed sir!. - welcome to the forum.

I see. Well, back it goes then.

Hi Grant,
Some initial thoughts I had when I viewed your diagram:

*By conservation of momentum, the accelerator would move toward Earth as it "kicks" the spaceship away from Earth. It will have to be "reset" occasionally.

*If the gravitational force between the spaceship and accelerator is what's providing the boost, you can calculate the mutual force via Newton's law of gravity; F = ma = GmM/r².

I think you'll find that "a," the acceleration, will be small unless "M," the mass of the accelerator, is huge.

*The spaceship will be attracted towards both spheres - not just the one above it. This will have to be taken into account.

*Also, with each launch, the accelerator will tend to slow in its rotation (again, via conservation laws). It will have to be "spun up" from time to time.

*For fun, you can use Newton's law of gravity, centripetal acceleration, and the definition of velocity (v=s/t) to calculate the altitude for a geosynchronous orbit. For a circular orbit, I get 35,862 km. Not bad considering rounding errors. The actual value is 35,786 km - well above the Karman line (100 km - above 99.9999% of the atmosphere).

Overall though, I think the force of gravity is just too weak to make this practical. Maybe think about a torus-shaped accelerator that uses the E-M force somehow. I picture the spaceship "charged" (somehow) and wizzing through the torus' center.

Cheers,
william

P.S. I did some plumbing in my house a couple years ago. It would have been nice to have someone like you around to answer questions.

Originally Posted by LeavingQuietly

You mean spinn the moon and stick some diamond edged spiderweb string to it? :?

I'm thinking of a large man-made satellite in earth orbit with a long tether attached to one end. You spin it up and use it to sling-shot spacecraft away from earth. The spacecraft approaches from a lower orbit, hooks on as the tether sweeps by and releases at the top of the arc.

Originally Posted by DarcgreY

Originally Posted by LeavingQuietly

You mean spinn the moon and stick some diamond edged spiderweb string to it? :?

I'm thinking of a large man-made satellite in earth orbit with a long tether attached to one end. You spin it up and use it to sling-shot spacecraft away from earth. The spacecraft approaches from a lower orbit, hooks on as the tether sweeps by and releases at the top of the arc.

However you look at it, any power you can impart to a space ship from your 'device' will cause a corresponding loss of power from your device - which will have to be restored, so if you manage to fling a ship in direction x,y,z your device will move -x,-y,-z. the energy you use to restore this is the same as the energy you imparted so in the end to be practical just give this energy to the spaeship and avoid all the complications of an extra stage in the process.

Originally Posted by Megabrain

Originally Posted by DarcgreY

Originally Posted by LeavingQuietly

You mean spinn the moon and stick some diamond edged spiderweb string to it? :?

I'm thinking of a large man-made satellite in earth orbit with a long tether attached to one end. You spin it up and use it to sling-shot spacecraft away from earth. The spacecraft approaches from a lower orbit, hooks on as the tether sweeps by and releases at the top of the arc.

However you look at it, any power you can impart to a space ship from your 'device' will cause a corresponding loss of power from your device - which will have to be restored, so if you manage to fling a ship in direction x,y,z your device will move -x,-y,-z. the energy you use to restore this is the same as the energy you imparted so in the end to be practical just give this energy to the spaeship and avoid all the complications of an extra stage in the process.

You'd be able to reduce the mass and complexity on all your craft with a sling-shot. Insert the spacecraft into the proper orbit with a single stage and let the launcher do the rest. For moon travel this would be much more efficient that having independently powered craft. You wouldn't need to lift the second stage with each shot, just the fuel to maintain the launcher in position.

in trying to understand this whole thread, i kind of wonder how a tube in space could add acceleration with less energy. that is if a craft entered a tube and accelerated would the speed of this be equal, more of less w/o a tube. is force dispersed in a vacuum and if so this dispersement being contained (to a degree) would this increase forward motion?

also if you try to answer this; can suction be produced in a vacuum?

Originally Posted by DarcgreY

Originally Posted by Megabrain

Originally Posted by DarcgreY

Originally Posted by LeavingQuietly

You mean spinn the moon and stick some diamond edged spiderweb string to it? :?

I'm thinking of a large man-made satellite in earth orbit with a long tether attached to one end. You spin it up and use it to sling-shot spacecraft away from earth. The spacecraft approaches from a lower orbit, hooks on as the tether sweeps by and releases at the top of the arc.

However you look at it, any power you can impart to a space ship from your 'device' will cause a corresponding loss of power from your device - which will have to be restored, so if you manage to fling a ship in direction x,y,z your device will move -x,-y,-z. the energy you use to restore this is the same as the energy you imparted so in the end to be practical just give this energy to the spaeship and avoid all the complications of an extra stage in the process.

You'd be able to reduce the mass and complexity on all your craft with a sling-shot. Insert the spacecraft into the proper orbit with a single stage and let the launcher do the rest. For moon travel this would be much more efficient that having independently powered craft. You wouldn't need to lift the second stage with each shot, just the fuel to maintain the launcher in position.

Ok

If you're not sure of what I say, try Newton's laws of motion, however you look at it, you need X, amount of energy to get a craft to the moon, the more 'slingshot' stages you have, the more loss's you incur (which will increase 'X' require these to be put [and kept] in orbit, maintained etc, just give the craft you wish to accelerate that energy to start with.

If you must look at an alternative to reducing propellant mass then look at launching winged vehicles from inclined linear motors. Similarly on the moon a linear accelerator could very efficiently launch a vehicle as there would be no air resistance.

Incidentally the second stage you refer to actually loses mass (propellant) as it 'flys' the amount of fuel required to reposition your slingshot would be the same amount - but you'd have to lift this fuel with yet more fuel...

It makes more sense to me to launch your second stage propulsion system once and refuel it than it does to launch your entire propulsion system with each shot. I guess it comes down to the energy requirements of refueling the orbital launcher as opposed to launching the weight of second stage systems with each shot.

Economically it would be cheaper in the long run to use a sling-shot.

it's ok to say refuel it, BUT you have to launch the fuel anyway! whether it's in stage two or 'added' later [via a slingshot makes no difference]except moving/pumping it in space would be very risky since the propellents are hypergolic in nature -

How about modular fuel cells that can be relatively easily replaced?

It depends how cheaply you can launch the fuel compared to a fully independent spacecraft. Anyway you'd save the cost of having to have expensive propulsion systems on each craft, after the intial cost of building the sling-shot.

Your calculation of 35,862 km... that's from Earth's center, right? Thanks for the formulas. I used to shy away from that kind of stuff until recently. The formulas I have to learn for my upcoming contractor's exam are about on the same learning curve, so I'm getting more and more used to handling math equations, but far from calling myself an intermediate. I'm trying to make heads or tails of it now.

Making it shaped the way it is and tumbling end over end was ridiculous. I first imagined it as a sphere (possibly a captured asteroid or something similar) and then drew it as it was on a whim. I'm bad about impulses like that.

Thanks for the response and the ideas. I realize I should scrap the idea (which I'm sure is nothing new) and look at the more practical solutions, but I'm having fun. And thanks for moving it back to where I started it.

Originally Posted by GrantG

Your calculation of 35,862 km... that's from Earth's center, right?

Good question! No, I subtracted the mean Earth radius to get that number thus making it an altitude.

Thanks for the formulas.

You're welcome!


You may find it humorous (since you're a plumber) that I got half way through installing a new washroom using PVC and CPVC before I realized that I needed to use primer before the PVC cement. Half the job done and then I had to start over. Live and learn.

Cheers,
william

Heh, yeah, I'm sure I've made that mistake even knowing good and well I needed it. When I was a kid, my friend and I made a potato cannon, but when we dry fitted the barrel to make sure it was the desired length, we couldn't get it to pull back apart in order to glue it. Instead, we decided that if we couldn't pull it apart with our bare hands, then surely it wouldn't come apart when we fired it. That was so wrong. So when I build my spacecraft launcher (link below), I'll be sure to prime it first.

http://www.freewebs.com/rockypeterso...ftlauncher.htm

Originally Posted by GrantG

Heh, yeah, I'm sure I've made that mistake even knowing good and well I needed it. When I was a kid, my friend and I made a potato cannon, but when we dry fitted the barrel to make sure it was the desired length, we couldn't get it to pull back apart in order to glue it. Instead, we decided that if we couldn't pull it apart with our bare hands, then surely it wouldn't come apart when we fired it. That was so wrong. So when I build my spacecraft launcher (link below), I'll be sure to prime it first.

http://www.freewebs.com/rockypeterso...ftlauncher.htm

Now that is an awesome rocket launcher!

There's a slight problem - I can see, I believe the burning rate of underarm deodorant is at most a few tens of metres/second. Escape velocity from the earth is [I think] 7 miles/second so you'll need several cans in parallel at least - with the amount of air in the tube, the flame will go out before the pressure is sufficient, why not lift the ship with a giant hydrogen balloon up to where it's 'captured' by the accelerator, then compress the Hydrogen for later use as fuel... 8)

interested in space propulsion?
see my new topic posted as Alcubierre drive, fact or fiction?(moved to astronamy catagory)

personaly i would attempt to steer away from using fuel in space,
i would instead focus on the proving of the existance of exotic matter...
and the applications of exotic matter as a way of propulsion.

i know this may seem strange to some but new inovations require a new prospective.

Originally Posted by Michael W. Bush

personaly i would attempt to steer away from using fuel in space,
i would instead focus on the proving of the existance of exotic matter...
and the applications of exotic matter as a way of propulsion.

i know this may seem strange to some but new inovations require a new prospective.

It should be possible in the future to have craft that require no fuel. Launch your payloads with EM cannons and use the slingshot I describe above for boosting craft into higher orbits or up to escape velocity for longer voyages. Payloads can also be used to maintain the slingshot in it's orbit, just have the mass transfer it's momentum to the accelerator.

Lightsails can also utilize light pressure from the sun in the inner solar system and Earth or Moon based lasers could power them farther out.