starship-design: scoops and sails and something to push against.

[Kevin Houston <kevin@urly-bird.com>]

Lee, 

You have given me a great idea (experienced list members will be ducking
for cover I assume ;)

let's rethink the idea of "engine", "scoop", and "sail"

scoop is a means of interacting with the interstellar medium.

engine is a means of accelerating the medium thereby moving us.

sail in this sense is a means of gathering energy.  a _trailing_ mesh of
some bits of silicon to turn UV radiation into electrical energy.

Please note, this is a very rough draft, there may be things I have not
thought out, I am thinking on the fly here.

What if a beaming system from earth simply created a "charge tunnel" in
the interstellar Hydrogen?  Then a ship could gather electrical energy
from a trailing sail, and use this energy to push against the charged
Hydrogen. perhaps using an oscilating electrical field.  The individual
hydrogen atoms, would not need to be drawn toward the ship, fused, and
expelled, but could be used in situ.  As the ship passed, each atom
would gain a small accel towards earth,  I think this would totally
eliminate the need for focusing the beam, earth would "paint" space a
fraction on an arc degree (limited by the wavelength of radiation
(ultraviolet would work best here)) around the target star, and the ship
could maneuver within that volume.  The entire engine would be outside
the ship!  the ship could be any size, but saucer shaped (to maximize
cross sectional area might be good) or cylindrical (to maximize
protection from speed induced radiation)

One main advantage is that you could establish this "charge tunnel" well
ahead of actual launch.

On the way back, you could wait to see the beam from earth before
heading back, and the hydrogen atoms that were accelerated towards earth
on the outbound trip would be accelerated towards Tau Ceti on the in
bound trip.

We have often wished for something to push against.

anyone care to shoot some holes in this?

Kevin Hosuton.




L. Parker wrote:
> 
> Timothy,
> 
> >
> > You may want to reconsider the following:
> >
> <Deleted>
> 
> In the particular instance of ramjets, you are correct that you have to be
> able to accelerate the reaction mass to greater than its original velocity
> relative to the ship. In addition, you must also do so without slowing the
> reaction mass down on its way through, that problem has been realized for
> quite some time. But I was speaking of reaction mass propulsion in general.
> 
> After looking back at the original statement, I see it was applied during a
> conversation about ramjets and was probably meant to apply to them
> specifically. But the way it was worded made it appear to apply to reaction
> mass thrust in general...a patently false idea.
> 
> The ramjet idea does have several difficulties to over come if it is to work
> however:
> 
> 1)      A solid scoop will never work. Even if a thousand or ten thousand meter
> scoop could be designed to withstand up to one tenth of a g of acceleration,
> as the velocity increased, the mass of the matter impacting it would go up
> proportionately. It would soon grow beyond any reasonable engineering.
> 
> 2)      If the scoop is immaterial, i.e. a field of some sort, then the same
> argument still applies although a little differently. As speed increases,
> the field strength must be increased without increasing the field area in
> order to prevent more and more of the matter from slipping through before it
> can be deflected far enough to bring it to the ship.
> 
> 3)      As you point out, all of this deflection must be done without generating
> so much drag from slowing down the fuel that we can't get enough thrust out
> of burning the fuel.
> 
> What I would suggest, is that IF we can generate a field sufficiently strong
> to catch ionized hydrogen, then we can probably generate one strong enough
> to function as a sort of inside out accelerator and simply magnetically (or
> whatever) propel the hydrogen backward without even bothering to burn it.
> The second possibility is that the field itself may be able to accelerate
> the matter as it is deflected inward, before it is burned thereby gaining
> additional thrust rather than drag.
> 
> Lee

-- 
Kevin Houston http://www.lpmn.org/candidates/
Libertarian candidate for Congress - District 5