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Re: New idea Laser launcher/scoop systems
- To: firstname.lastname@example.org (Kelly Starks x7066 MS 10-39)
- Subject: Re: New idea Laser launcher/scoop systems
- From: email@example.com (Kelly Starks x7066 MS 10-39)
- Date: Wed, 6 Mar 1996 15:15:52 -0500
- Cc: Steve VanDevender <firstname.lastname@example.org>, email@example.com (Kelly Starks x7066 MS 10-39), Brian Mansur <firstname.lastname@example.org>, David <David@interworld.com>, hous0042 <email@example.com>, jim <firstname.lastname@example.org>, KellySt <KellySt@aol.com>, lparker <email@example.com>, rddesign <firstname.lastname@example.org>, "T.L.G.vanderLinden" <T.L.G.vanderLinden@student.utwente.nl>
At 3:08 PM 3/6/96, Kelly Starks x7066 MS 10-39 wrote:
>At 11:40 AM 3/6/96, Steve VanDevender wrote:
>>Kelly Starks writes:
>> > Hi,
>> > A couple days back, Tim ran threw the numbers to show what acceleration a
>> > 'fuel packet' would need to get it up to 1/3rd light speed. Assuming a 100
>> > meter long launcher, the numbers came out at E14 m/s^2 I.E. 10 trillions
>> > G's. I was obviously upset to hear this. However that information and a
>> > flip comment I made about the size of a fuel packet ("it could be as big as
>> > a freight car if you wanted") combined.
>>Actually, now that I think about it there is a dangerous likely flaw in
>>this fuel launcher idea.
>>Remember a while back when I ran the numbers on fuel-to-payload ratios
>>for different fuel types? Remember that hydrogen came out at _minimum_
>>to need 1,000,000 units of hydrogen to one unit of payload to reach even
>>low relativistic speeds.
>>So, suppose we do prelaunch fuel along the ship's track, on the
>>assumption the ship will catch up to the fuel and can then pick it up
>>and use it to decelerate. For each chunk of fuel, how much ship mass
>>can that chunk effectively decelerate? Not bloody much if the ship is
>>travelling at relativistic speeds. The fuel packet may not be able to
>>decelerate its own canister down from 1/3 c, let alone any useful
>>fraction of the ship. At 1/3 c, you'd have to put more energy into
>>accelerating the fuel than you could get out of the fuel.
>>If we could launch chunks of antimatter, it would be no problem. But
>>the fundamental problem is that hydrogen fusion is nowhere near
>>efficient enough to reach high relativistic speeds; even with 1000:1
>>fuel-to-payload ratios you can't get near 1/10 c.
>I ran some numbers for fuel to ship mass ratios to get to (or down from)
>various speeds, depending on the spec impulse. (I think that was one of
>the docs I sent around for review. 1/10th was fairly easy, 3/10 ths became
>obsurd without well over 2,000,000 spec imp fuel. Higher then .3c and you
>get a geometric escalation of fuel to weight ratios. (Which is why I never
>consider them for internally fueled operations.)
>The fuel launched by the launcher, will take more energy to launch then it
>will return, but it will return it on the ship. Look at it this way, the
>microwave beam systems will probably need to beam hundreds of times (maybe
>thousands of times) the power that the the ship will catch. Other wise
>there's to much risk the sail will drift part way out of the beam, or into
>a weak area of the beam.
>We are not going to be able to do this without a fantastic amount of power.
>Which means a huge support infastructure.
>Lifes tough with those kind of speeds.
Opps forgot to add the mass ration numbers. :(
Speed 50,000,000 m/s (1/6 light
Speed 100,000,000 m/s (1/3 light
7 to 1 mass ratio.
55 to 1 mass ratio.
12 to 1 mass ratio.
148 to 1 mass ratio.
27 to 1 mass ratio.
785 to 1 mass ratio.
Notice the mass ratios vary rapidly with changes in spec impulse and total
delta-V. Anyway if we can get 2,500,000 spec impulse, stoping the ship
from .3 c is possible given some real good equipment! But notice how much
more fuel this takes then externally feed mode!
Kelly Starks Internet: email@example.com
Sr. Systems Engineer
Magnavox Electronic Systems Company
(Magnavox URL: http://www.fw.hac.com/external.html)