Space shuttle for space tourism and first stage of a TSTO.
Robert Clark wrote:
On Jan 19, 5:56 pm, Robert Clark wrote:
...This page gives the specifications of the Ares I:
Space Launch Report - Ares
I.http://www.spacelaunchreport.com/ares1.html
The gross weight including payload is given as 912,660 kg and the
gross weight of the first stage as 732,550 kg. So the gross weight of
the Ares I second stage plus payload is 180,110 kg.
Then the gross weight for the 55,442 kg dry weight of the
reconfigured shuttle, plus 300,000 kg propellant load, plus 180,110
kg second stage and payload is 535,552 kg, 1,178,214 lbs. But the 3
NK-33 engines I was suggesting to use only put out a total of
1,018,518 lbs. of thrust at sea level. For this purpose you would
need a fourth
NK-33. The dry weight is now 56,664, the gross weight is 536,774 kg,
1,180,903 lbs., and the sea level thrust of the 4 engines is
1,358,024 lbs.
Using the average Isp of the NK-33 as the midpoint of the sea level
and vacuum Isp's at 315 s, the achieved delta-V would be 315*9.8*ln
(536,774/(56,664+180,110)) = 2,527 m/s, comparable to the equivalent
delta-V, speed + altitude, provided by the Ares I first stage. The
achieved delta-V is actually higher than this since the rocket spends
most of the time at high altitude, where the Isp is closer to the
vacuum value.
Note that if you want to increase the delta-V, the space occupied by
the crew compartment is now empty. This gives an additional 74 cubic
meters that could be used for propellant, which amounts to 74,000 kg
additional lox/kerosene propellant that could be carried.
Then we could still use the planned upper stage of the Ares I while
having a significantly lower development cost and per launch cost of
the now reusable first stage.
If we only instead wanted suborbital tourism for the vehicle then you
would require much less fuel load. Having engine-out capability is a
necessary requirement for manned flights. According to this page, the
shuttle has a max emergency landing weight of 240,000 lbs, 109,000 kg:
Space Transportatin System.
http://science.ksc.nasa.gov/shuttle/...l#launch_sites
In the calculation in the above post, after removing several
subsystems that wouldn't be needed for an unmanned first stage booster
I got a 55,442 kg dry weight using three NK-33 engines. However, for
suborbital tourism we need the crew seats and environmental systems so
I'll add back the 3,250 kg for these to get a dry weight of 58,692 kg.
Now assume we max our fuel load for the suborbital tourism use at
50,308 kg, so our max takeoff weight is 109,000 kg, the max allowed
for the shuttle for landing under abort modes. Then our delta-V
assuming a 315 s average Isp of the NK-33's would be:
315*9.8*ln(109,000/58,692) = 1,911 m/s. This is well above the total
equivalent delta-V, speed + altitude, required for reaching the 100 km
altitude for space tourism. And the achieved delta-V would actually be
higher than this because the actual average Isp is closer to the
vacuum value than to the midpoint value.
Note that in this configuration we even have 2 engine-out capability
since the thrust put out by the NK-33's at sea level is over 300,000
lbs. And since our max weight is at the max allowed for landing the
vehicle could even glide to a landing with a full fuel load if all
three engines failed as long as we did reach high enough initial
velocity for aerodynamic lift to operate. (The orbiter has a
respectable lift/drag ratio of 4.5 at subsonic speeds.)
Keep in mind that not even jet airliners can land safely during an
aborted takeoff if they have all engines out unless they reach
sufficient altitude and velocity for lift to operate.
If "lift" was not "operating" then an airliner would not have reached _any_
altitude.
cretin.
plonk
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