[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: new web site/status report

On 4/10/96 at 10:35 am EDT, Kevin wrote-

>(At 1G continuous thrust)...Even the antimatter rockets can't
>get up to .99 lightspeed with a mass ratio of 52.

Two points--

1. With the saturation of apparent velocity, the implications
of .99 lightspeed are obscured.  A peak apparent velocity of
0.99 ltyr/yr represents a peak proper velocity of 7.0179
ltyr/yr and an acceleration distance (at 1g) of 5.90 ltyr.
(I.e., a destination distance of 11.8 ltyr with 1g deceleration,
also.  BTW, my astronomy book gives the distance to tau Ceti as
10.3+/-0.3 ltyr.)  What mass ratio does MARS require to decel-
erate at 1g from this peak velocity?  (I think that's the 52,
from Timothy's 3/30 table, that you're quoting, which is for
100 percent conversion of captured microwave energy to exhaust
kinetic energy.)

2. An optimum antimatter rocket with a peak proper velocity Uend
of 7.0179 ltyr/yr has an optimum constant exhaust velocity Vexh
of 0.8851.  The required mass ratio (r = exp[asinh(Uend)/Vexh])
is 19.89.  (These calculations assume no energy losses, but also
assume no gain from optimizing the exhaust-velocity profile.)

Regards, Rex