# Re:

```At 4:59 PM 3/11/96, Kevin C Houston wrote:
>Here is a table of some maser sail numbers.
>
>I think that 50 g/m^2 is kind of heavy, but as Tim said, this is going to
>be subject to some severe torture.  Perhaps the RR will sweep away the
>ICM particles, but I don't know.  No matter what the final density is,
>i think these numbers will behave the same way, (ie limiting values on
>
>Ship's  Sail  Sail   Sail    Total   Accel   Maser   Refl  Excess  Stress
>Mass   Radius Dens   Mass    Mass            Energy  Eff.  Energy
>Kg       Km   g/m^2   Kg      Kg     M/s^2   Watts    %    KW/m^s  Pascals
>5E5      10    50   1.57E+07  1.6E+07  10  2.43E+16  0.99  773.8  0.515915
>5E5     100    50   1.57E+09  1.6E+09  10  2.36E+18  0.99  750.2  0.500159
>5E5     500    50   3.93E+10  3.9E+10  10  5.89E+19  0.99  750.0  0.500006
>5E5    1000    50   1.57E+11  1.57E+11 10  2.36E+20  0.99  750.0  0.500002
>5E5    5000    50   3.93E+12  3.93E+12 10  5.89E+21  0.99  750.0  0.5
>5E5   10000    50   1.57E+13  1.57E+13 10  2.36E+22  0.99  750.0  0.5
>5E5  100000    50   1.57E+15  1.57E+15 10  2.36E+24  0.99  750.0  0.5

Numbers!  Great!

>Ship's mass is just the hab section  (no core, no RM tanks)
>sail density does not include guy wires to the ship.
>Excess energy is the part of the maser beam that does not reflect

Ship mass would have to be more than just the hab deck.  Also would have to
be more than you've shown.  If I'm reading this right, the ship weighs 5E5
kg.  Which is only 500 tons.  You might want to add 2-3 zeros to that
number. ;)

>Several things have become clear to me since I ran these numbers (in Excell)
>and I should think they will become clear to you as well.
>
>1) the sail is the heaviest part of the ship.  Even at 50 g/m^2, and 100
>Km in radius, the sail alone approaches my original MARS design (now a
>smoking ruin ;( )

We'll see.

>2) both thermal energy and sail stress approach some limiting value as
>the sail expands, so endlessly expanding the sail (even if we could do
>it) would not solve any of the major problems (heat load and stress)

That would depend on the thrust needed.  I agree that the stress factor is
minimal.

>3) Stress is miniscule  I don't where you guys have been getitng your
>stress numbers, but they are out of whack.
>
>for figure checking, reading line 3 with a sail of 100Km radius, and a
>total mass of 1.57E9 Kg we find that the force of acceleration is
>1.57 E10 newtons, and the total area is 3.14 E10 meters which of course
>is .5 pascals (even a wet nose tissue could stand up to that)
>
>4) smaller sails may be better.  Why in the world you would need a sail
>the size of Luna, much less Jupiter, is beyond me.
>
>5) Thermal load is a big problem.  750 KW on .05 Kg is a big worry.
>I have not calculated the limiting temperature yet, but I am hopeful that
>titanium alloy will stand up to the load.  To do this model, I will use
>heat capacity and blackbody radiation equation.  I do not have time right
>now, but expect it soon.
>
>
>Kevin

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

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