Hello everybody,
just checking on some rules interpretations. There is a payload
in Mars orbit that needs to go down.
* The lander has a solid fuel rocket for the de-orbit burn. This
is mounted on a hardpoint. The solid rockets are listed in one
minute increments, so the TL8 rocket would be 10.8 lbs. for 1
lb. of thrust for 1 h. Of that, 9.18 lbs. are fuel and 1.62
lbs. are casing, so Isp according to VXii32 is 392.
An 1,800-lb. solid rocket on a 20,000-lb. lander would be 680
mph or 303 m/s. That should be enough to get into aerobraking
altitude.
* There is a disposable, aerodynamically shaped heat shield. The
shield is an exo-husk according to VXi28.
- Applique armor is limited to fair or lesser streamlining.
The exo-husk rules don't mention this limitation, but they
refer to the applique rules. So can I have very good
streamlining and a lifting body on my exo-husk?
- Can I give the streamlining to the husk, but not to the
vehicle itself? That would mean the lander can safely
exceed the speed of sound with the heat shield in place.
The nominal volume of the exo-husk would be 1.25 times the
actual body volume, to follow the usual VE2nd 'fake volume'
system.
* If the heat shield and thus the lifting body are gone, the
lander no longer qualifies for the glide speed rules, but
the terminal velocity calculation on VXii30 should still
apply. A 500-sf, 16,000-lb. lander would have a terminal
velocity of 490 mph on Earth, or 1,880 mph on Mars since
the lower gravity is countered by a lower air density,
which effectively gives the effect of radical streamlining
(VE166).
* VE71 says that parachutes just plain won't work, but that
is a simplification. My plan is to use an external impact
absorber (VXii18) rated for 200 mph.
For the required parachute area, I'm a bit lost, since
the VE rules don't have a listed area. Out of thin air,
I'm taking a nominal 16,000-lb. parachute.
The exo-husk and parachute interpretations are the most iffy
ones, while the rocket stuff is fairly straightforward. Does
that make sense to you?
Regards,
Onno
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