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RE: Old RAIR drive system

At 5:27 PM 3/5/96, Brian Mansur wrote:
> ----------
>From: kgstar
>To: KellySt; hous0042; T.L.G.vanderLinden; stevev; jim; zkulpa; rddesign;
>David; bmansur; lparker; kgstar
>Subject: Old RAIR drive system
>Date: Tuesday, February 27, 1996 1:38PM
>>From Brian 5:00 PM CT 3/5/96
>>Heres some more text to look over.  Attack at will.  This was what I
>>consider the baseline drive system for my Explorer class design.  Untill I
>>figured out it probably wouldn't work.
>Ready.  Aim, Fire!
>[Begin Excerpt]
> -----------------------------------------------------------------------
>multi-cycle Ram Augmented Interstellar Ramjet (RAIR)
>Spring 1995
>A drive idea I came up with, and used as the assumed system for this ship,
>is A multi-cycle Ram Augmented Interstellar Ramjet (RAIR). It would scoop
>up reaction mass from interstellar space like a pure ram scoop, but it
>would only use it as reaction mass, not fuel. But the scoop system could
>simultaneously scoop up fuel thrown ahead of the ship by a fixed launcher
>back in our solar system.
>The system is basically an electromagnetic accelerator running through the
>core of the ship, powered by onboard fusion reactors. The accelerator could
>accelerate scooped-up interstellar matter (or ram flow), or reaction mass
>carried in the ship. Again, this kind of system is different from a true
>Bussard ramscoop drive in that the ram flow is not fused for power. Indeed,
>it normally isn't even slowed down. The engine functions in various ways at
>various speeds.
> ------------------------------------------------------------------------
>[End Excerpt]
>Okay, this basically says that you overcome drag by not slowing the RM when
>you run into.  We still need numbers on the power required to ionize the RM.
> I have the feeling that it will be way over what we can produce with our
>fusion powerplants.  This says nothing about how much fusion fuel we'd have
>to carry.

Unfortunatly, the best info we have is that there isn't enough reaction
mass in space to make this desirable.  So I never worked it out to that
level.  I'ld drop it, but it is an interesting class of drive systems.

>[Begin Excerpt]
> -----------------------------------------------------------------------
>Acceleration To InterStellar Cruise
>[Text deleted]
>The idea I came up with to get around this fuel problem is to launch the
>fuel ahead of the ship with orbital accelerators (thus the externally
>fueled part of the name). The accelerators back home throw out HUGE
>quantities of frozen pellets of whatever fusion fuel is selected, in the
>path of the ship (called the acceleration track). The fuel is launched at
>measured and timed speeds, so that the ship will encounter a fairly steady
>stream of fuel during its run down the fuel loaded acceleration track.
> ----------------------------------------------------------------------
>[End Excerpt]
>Problem here.  You want to accelerate HUGE quantities of fuel and RM up to
>at least 1/3c.  Where do you get the power for this?  To do it you'd need
> almost if not more power than a maser array would (groan).

In this system the 'huge' comment was assuming we'ld throw out enough
excess so that some fraction (i.e. enough to run the ship) would be close
enough to the ships course for it to scoop up.  I haven't worked up the
power numbers yet.  Mass numbers would depend on the recovery %.  But
compared to the weight of onboard fuel needed to do the same, its fairly
light.  Say 50-100 times the loaded ships mass.

Frankly I don't know if the sun makes puts out enough power to run the
masers! ;)

>>As the ship accelerates, it catches up with fuel going at increasing
>>but always at speeds slightly slower than the ship itself.
>Let me see if I understand something here.  You are laying a track of fuel
>that runs slow at first.  Then you plan on having the ship catch up to
>faster RM as you accelerate.  Have you laid the whole track out before you
>launched.  If so, you'd have to fire slower RM pellets first, then the
>faster moving pellets.  If this is done all along a straight track, you may
>have some fuel bumping into slower fuel.

You start out launching slower fuel and add faster and faster fuel as the
ship accelerates.  The launcher has to throw it ahead of the ship, but not
so soon that the ship couldn't catch up with it untill the ship was going
to fast to pick it up.  Nor so late that the fuel wouldn't catch up with
the ship.

Fuel packets/canisters could hit one another, but that should be infrequent
enough so we don't lose unacceptable amounts of fuel.

>Also, the rate of fuel launching increases as  you have to launch  higher
>velocity fuel.  Otherwise your faster fuel speeds ahead of the slower
>pellets and the Asimov can't accelerate fast enough to catch up.  Also, if
>it tries to accelerate too fast in a fuel stream with predetermined
>velocities along any given part of the stream, you start to get drag.

I'm not sure I follow this part.  Did I answer it above?



Kelly Starks                       Internet: kgstar@most.fw.hac.com
Sr. Systems Engineer
Magnavox Electronic Systems Company
(Magnavox URL: http://www.fw.hac.com/external.html)