Re: drifting back OT (was: Drifting to DSII (was Re: New Fighter Types (drifting OT....)))

> >> you don't want to know how i
> >> figured it out, do you? 
> >
> >Actually, I do. 

damn.

> >Mass is easy enough, but the simplest formula for
> >potential energy (E=mgh) has two problems: It assumes constant
gravity and
> >ignores atmospheric friction.

i calculated the change in gravitational potential (energy per unit
mass) between orbit and surface and multiplied by the mass of the rod.
if potential is P, the gravity constant is G, the planet's mass is M and
the distance is r, then P=GM/r; if potential energy is E
and mass is m, E=Pm; thus E=GMm/r, and so dE=GMm(1/r - 1/r') where dE is
change in energy and r and r' are the orbit and surface radii
respectively; the dE comes out negative, as the rod is losing energy to
the target.

the titanium alloy i am using is now Ti-6Al-2Sn-4Zr-2Mo, Duplex
Annealed, which has a density of 4.54 g/cm3 and a melting point of ~1700
C. not that a liquid impact is any less dangerous; i don't know at what
temperature the Ti begins to burn. i got this data from
http://www.matls.com/search.htm.

> >Taking that orbit is "high enough", you need to calculate the
terminal
> >velocity for the rod and go from there. I trust you did this?

afraid not. the figure i gave is for bombarding an airless planet :-).

> >I'll forgive you for ignoring heat build-up effects from atmospheric
> >friction.

thanks. the rod could have a cap of heat-resistant or ablative material
to protect it.

i remain, exposed in my pseudoscientific pretentiousness,
Tom

BTW i am going for the record for longest subject line.