Newsgroups: sci.space
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: Room Temperature fusion - possible indications?
Message-ID: <1989Mar28.173557.21601@utzoo.uucp>
Organization: U of Toronto Zoology
References: <290@vlsi.ll.mit.edu> <1098@Portia.Stanford.EDU> <296@v7fs1.UUCP> <5849@pdn.nm.paradyne.com> <1989Mar26.003753.11770@utzoo.uucp> <5853@pdn.paradyne.com> <24998@amdcad.AMD.COM>
Date: Tue, 28 Mar 89 17:35:57 GMT

In article <24998@amdcad.AMD.COM> prem@crackle.amd.com (Prem Sobel) writes:
>Unless I have slipped a decimal point. It is under 1.6*10^9 miles round
>trip to/from the asetroid belt...
>which if one went at 1g until half way then at 1g to slow down would take:
>	t=sqrt(5280*10^8) ~= 73*10^4 sec ~=200 hours ~= 9 days

Accelerating at 1G (9.81 m/s/s, the Imperial units are useless garbage
when it comes to calculations like this) for 200 hours is a total
delta-V of about 7e6 m/s (7000 kps).  If we assume a mass ratio of 10,
which means the ship is mostly fuel but still manageable for a single
stage, exhaust velocity is 7e6/ln(10), about 3000 kps.  Assuming a
100-ton (metric) ship (fully fueled), we "burn" 0.125 kg/s.  (We will
ignore the change in thrust needed to maintain a constant 1G, and
assume constant thrust for the moment.)  Accelerating that mass flow
to 3000 kps requires 0.5*0.125*(3e6*3e6) == 560e9 watts of power,
assuming no losses.  Building a half-terawatt power plant that weighs
only a few tons is going to be, um, a challenge.  I don't think we're
going to see 1G missions to the asteroids right away.
-- 
Welcome to Mars!  Your         |     Henry Spencer at U of Toronto Zoology
passport and visa, comrade?    | uunet!attcan!utzoo!henry henry@zoo.toronto.edu