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Re: Engineering Newsletter

Replyto : Timothy

>>> Externally fueled did that mean scooping? I'm not sure 
>>> anymore, please tell me if my assumption is right.
>Not quite.  In my Exporer ship design I assumed the fusion fuel was launched
>ahead of the ship with a linear accelerator.  As the ship accelerates it
>contiually scoops up pre launched fuel going at nearly its speed.  So the
>ship looses very little momentum scooping up the fuel packets.  That would
>allow you to get up to light speed with "only" 200 times the ships mas in
>fusion fuel.  However like Kevins system.  We have a serious problem
> I though using a ramscope to produce a lot of drag might do it, but never
>found a good woorkup of the numbers.

>> This method of prelaunching fuel packets will cost the 
>> same amount of energy that is needed if you take those 
>> same packets with you from the start.

True, but since the ship doesn't have to supply the energy, it saves an
incredable amount of fuel.  To put it bluntly no fusion powered ship could
carry enough fuel, to accelerate itself and its fuel up to high reletivistic
speeds.  Estimates are that a ship would need a 1,000,000 to 1 fuel to ship
mass ratio to get up to $10 of light speed.  But if the ship doesn't have to
carry its fuel, a 200 to 1 ratio could get you most of the way to light speed
(or was that 1/3rd light speed.  Been a while since GES ran the numbers off
for me.)

>By the way.  Did anyone calculate the drag on the sail structure from
>interstelar debre?  If you can maintain enough of an electric charge to use
>the microwave sail as a parachute that might help with stoping.

>> The problem is that there are no accurate numbers of 
>> the density of interstellar debris. So any number is almost 
>> a guess.

Thats been a constand problem for us.  How do you design a ship to travel
through something you know next to nothing about?


>Diverted beams of photons converge on a forward pointing cone.  This (not
>considering the beam cancelation due to interfearence, reflection loses, and
>other such nonsence) is the origional beam moving forward in a much more
>concentrated form than its pre sail moments.  Net thrust to the ship near
>(give or take).  In frount of this stream we put an ionized reaction mass.
> Beam slams into it and throws it forward.
>A) A lot of the beam (most?) would reflect back off the ionized reaction
>(micro-waves do that off ionized matter)  Would this act as Forward's
>sacrificial outer-sail in "Dragons egg (?)"?  I.E. could we use the
>reflected beam for drive power?  Efectivly the reaction mass (now renamed
>plasma reflection mass) has gotten boosted forward at a hellish speed, but
>bounced the beam back down our throats.  (Just like Forwards outer drop
>sail.)  We would have to continuously replenish this "reflection mass", but
>on the bright side we could be very sure it will clean all the interstellar
>mass out from in frount of the ship.  ;)

>> Replenishing the "mirror" will probably take lots of ions 
>> or in other words mass that has to be taken with us. 

Agreed, but it don't have a handel on the amount of mass.

(Hey it sounds better than Forwards ring sail trick.)

>> Also using such a light (non heavy) sail will mean that 
>> the "mirror" is accelerated a lot and lot of energy is lost
>> due to the Doppler effect.

Given that the mirror is the surface of a plasma, and said plasma is being
continuously being replenished.  I'm not sure the reflective "surface" is
actually moving?  Althou obviously the particals in the plasma are moving
(and accelerating) rapidly.  Are the micro waves reflecting off the
particals?  Or off the area where the plasma is ionized enough to reflect

>> Also I have doubts how well the "mirror" reflects, ionized 
>> particles attract or repell each other so, it won't take long
>>  befor the "mirror" has destroyed itself.

The ions in a plasma of the same material wil repell each other.  You might
be able to do some magnetic tricks to hold it, but it probably wouldn't be
worth the trouble.

[ Hum --- I wounder if you could wiggle the exausting plasma to for a laser
to get back some of the energy? ]

As to reflectivity.  That would depend on the nature of the plasma and a lot
of other variables.  This is probably not a question we could easily figure
out for ourselves.

>Instead of just dumping this superheated reflect mass forward.  How about
>using it as a rocket stream also.  At the least we can ride the expanding
>shock wave from the stuff.

>> Shock wave? I don't understand, please explain again.

You have a mass of plasma being hit with E18 of energy.  It will be HOT, and
highly ionized.  It will be explosivly expanding.  The light pressure of the
beam (or the feed mass) will probably keep it from flowing straight up the
beam.  But it will be moving rapidly to the sides and forward or the ship.
 We should be able to tap this for thrust.

>Anyway, between A & B we have used part of the beam to create a high temp
>plasma thurst, and reflected the rest off said plasma onto a rearwardly
>reflective part of the ship. Momentum/kinetic energy interactions between
>the beam and the ship are pretty much canceled out until it hits the
>reaction/reflection mass.  The ship needs NO POWER CONVERTERS!  We never
>convert it to electricity to drive an accelerator.  (Ok, ok, we convert a
>little to run the ship and power the magnetic feilds that keep the plasma
>the back of the ship.) But other than that, we just reflect it around and
>feed it mass.


Steve writes:
>The reality that static stress does not continue to dissipate
>energy over time is not intuitive, because our muscles aren't
>static structures like boards or rods or wires; they must
>dissipate energy even to hold a weight motionless above your
>head, while a table holding the same weight does not dissipate

>> Yes, in fact is does not take any energy to keep floating a
>> few metres above Earth's surface.

(???????!!!!!!)  SAY WHAT!!  Unless we're on differnt planets you have to
generate or disapate as much energy as to generate 9.8 m/s^2 of acceleration.

Kelly Starks