SSTO to LEO, 80,000 pound payload or Bust. [was Bigelow launch vehicle mistake]

David M. Palmer wrote:
In article .com,
H2-PV NOW wrote:

We learned that an air-launched vehicle carried by a B-52 can do
orbital insertion and can carry useful payload. We learned that stubby
wings are adequate to give useful lift for fuel conservation to
altitudes where the air is appreciably thin.
http://en.wikipedia.org/wiki/Pegasus_rocket

That's funny, I read the same link:
http://en.wikipedia.org/wiki/Pegasus_rocket

It said: "Payload: 443 kg (1.18 m diameter, 2.13 m length)"

I guess we have different definitions of "useful payload". Mine
resembles the cargo container commonly transported by trailer of an
18-wheeler, 8'x8'x40' with 80,000 pounds, that can go on ships, trains
or highway trucks. That fits in the cargo bay of the Spaceplane and
delivers it to ISS or equivilent.

Yes, I guess we do have different definitions of "useful payload".

If anything less than 10x the payload capacity of a DC3 is useless,
then space will not be useful at a reasonable price for a very long
time.

ISS is just 220 miles away. If you refuse to fly payloads the 75 miles where air can partially help carry the
load, then you have a problem. The exact same Newtonian physics apply to winged lift as to rocket thrust. In
the rocket case you are spitting out molecules in the reverse direction you want to go. In the plane case you
are ricocheting molecules off the lifting undersurfaces of wings. It is equal and opposite reaction in both
cases. One obviously takes more fuel, which penalizes the payload.

http://en.wikipedia.org/wiki/Skylon
SKYLON is designed to fly to space. Whether it gets there depends on the success of the air-loading of
oxidizer at high altitude.

Skylon Statistics:
* Length: 82 m
* Fuselage diameter: 6.25 m
* Wingspan: 25 m
* Unladen mass: 41,000 kg
* Fuel mass: 220,000 kg
* Maximum payload mass: 12,000 kg
* ISP: 2000 to 2800 s (20 to 27 kN·s/kg) atmospheric, 450 s (4.4 kN·s/kg) exoatmospheric
* SABRE engine thrust/weight ratio: 10

Most of the concepts are sound. It's the technological implimentation of them which is in question. Certain
machinery must work perfectly at mach 5 at 100,000 feet.

As you yourself pointed out, space launch from high altitude firing of rockets is proven by Pegasus and
others. Flying to launch altitude (the mother ship) is also obviously proven. Combining the concepts in one
SSTO is what has not been proven, but Pegasus + B-52 = LEO has been proven.

Getting airborne with a heavy load is proven:
http://en.wikipedia.org/wiki/C-5_Galaxy

Specifications (C-5M)
# Wing area: 6,200 ft² (576 m²)
# Empty weight: 337,937 lb (153,285 kg)
# Loaded weight: 769,000 lb (348,810 kg)
Performance
* Maximum speed: 570 mph (917 km/h)
* Range: 3,749 mi (6,033 km)
* Service ceiling: 34,000 ft (10.36 km)

Getting to high altitude on low power is proven:
http://www.nasa.gov/centers/dryden/n...-068-DFRC.html
In 2001, the Helios Prototype achieved the first of the two goals by reaching an unofficial world-record
altitude of 96,863 feet and sustaining flight above 96,000 feet for more than 40 minutes during a test flight
near Hawaii. ...

Aircraft Description
The Helios Prototype is an ultra-lightweight flying wing aircraft with a wingspan of 247 feet, longer than the
wingspans of the U.S. Air Force C-5 military transport (222 feet) or the Boeing 747 commercial jetliner (195 or
215 feet, depending on the model), the two largest operational aircraft in the United States. ... The wing
area is 1,976 sq. ft., which gives the craft a maximum wing loading of only 0.81 lb./sq. ft. when flying at a
gross weight of 1,600 lb.

The wingloading on the C-5 is 124 pounds per square foot of wing. The wingloading on the Helios was 13
ounces per ft^2 of wing.

The wingloading on the 747-400 is 141 pounds/ft^2.
http://en.wikipedia.org/wiki/Boeing_747

The wingloading on the Concorde was
http://en.wikipedia.org/wiki/Concorde 105.9 pounds/ft^2

As you can see heavy loads can get airborne, fly somewhat high, somewhat fast with quite long ranges
exceeding 220 miles.

The SR-71 Blackbird flew both high, far and fast...
http://en.wikipedia.org/wiki/SR-71_Blackbird
Wing area: 1,800 ft² (170 m²), Maximum gross takeoff weight: 172,000 lb (78,000 kg), Maximum speed: Mach
3.35 (1,906 knots, 2,193 mph, 3,530 km/h) at 80,000 ft (24,285 m), Maximum altitude: 100,000 ft (30,500 m).
The wingloading on the SR-71 was 95.5 pounds per ft^2.

The plastic Helios flew at the maximum altitude of the SR-71, using propellers, powered by 28 horsepower of
electric motor fuels by solar cells glued on the wings.

The blackbird had a rate of climb of 60 ft/sec, almost double the pull of gravity, meaning some design
changes and it could keep on climbing. That same sustained rate of climb for a little over 5 hours would put
it at ISS doorstep.

The Blackbird, as it was could not carry the fuel for five hours of thrust expendature. Plus it didn't carry it's
oxidizer, being an air breather. Plus, it's wings were not big enough as the air thinned further to ricochet off
air particles to sustain climb.

What all this makes clear is spaceplanes need to have much larger wings so that air does a lot of the lifting
work where air can help.

http://www.sprucegoose.org/aircraft_...its_cont1.html
The Spruce Goose had the largest wing area ever made, 11,430 square feet, and it's wingloading was a
modest 35 pounds/ft^2.

The point being that more wings means lower wingloading, which means less fuel consumption to fly high.
The Skylon has too little wings, although the wing area cannot really be figured from the webpages I have
looked at. Deficiency in wings means faster fuel consumption to stay at peak altitude for air-breathers, and
that cuts the the available time to onload oxidizer at high altitude.

Oxygen is 16 atomic weight units. Hydrogen is one. LH2/LOX rockets burn a rich mixture of 4H2 per O2.
That means 8 atomic weights of Hydrogen mass per 32 atomic weights of Oxygen. The ratio is 1:4 fuel
oxidizer by weight. Slush-LH2/LOX rockets burns 3H2 per O2 or 3:16 ratio by weight. The oxidizer is 3 to 4
times the weight of the fuel.

SKYLON's strategy is to load that heavy O2 and chill it to LOX by using the coolth of LH2 fuel. The problem
they will have is they don't have enough time to complete the manoeuver because their small wings cost
them too much fuel to dawdle at that altitude.

The biggest problem is air is 80% Nitrogen and only 20% Oxygen, by weight. N2=28, O2=32 atomic weight.
Too much N2 will be adsorbing heat and need to be dumped overboard. They cannot linger at this altitude.
In order to hurry the operation they will be accelorating to Mach 5. The disposal of the weighty and useless
N2 has to be accomplished pell mell. Equipment subjected to cryogenic temperatures and enormous
airspeeds must work flawlessly, efficiently and rapidly in a mach 5 hurricane force winds.

When all this is said and done, their payload will only be 26,455 pounds to minimum LEO orbit, less payload
if going to higher orbit. If they succeed.

Larger wings means more fuel can be economically carried up to 100,000 feet. Larger wings means that you
have more low-fuel consumption gliding time at 100,000 feet. Remember, this was the same altitude that
Helios flew with nothing more than solar powered 28 horsepower motors. Larger wings means more payload
can be lofted this high on lots less fuel. At 100,000 feet the air density is very much less than 1/10th of sea
level. That means that your wingloading must be fairly low for aerodynamics to sustain lift because there are
far fewer particles of air ricocheting off your lifting undersurfaces. Either your wingloading must be small or
you have to be going very fast to keep from sinking.

You can get to LEO with little or no wings, but it has tremendous fuel consumption penalties, and you will
pay twice on re-entry. LEO is not some abstract goal to achieve. There's no point in going in the first place if
you can't deliver hefty amounts of supplies.

http://en.wikipedia.org/wiki/Space_S..._External_Tank
The disposable External Tank of the Space Shuttle has the following dimensions:
The ET is the largest element of the space shuttle, and when loaded, it is also the heaviest. It is 153.8 feet
(47 m) long and has a diameter of 27.6 feet (8.4 m) and has three major components:
* the forward liquid oxygen tank
* an unpressurized intertank that contains most of the electrical components
* the aft liquid hydrogen tank; this is the largest part, but it is relatively light.

From the above I compute that the tank has the surface area of roughly 13,266 ft^2. That is slightly larger
than the wing area on the Spruce Goose. The surface area of the two Solid Rocket Boosters combined is
approximately 11,889 square feet.
http://en.wikipedia.org/wiki/Space_S...Rocket_Booster

There is more than enough material between these two to make wings large enough to give a low
wingloading to a very heavy vehicle with the weight distributed.

Heretofore there has not been conformable cryogenic fuel supply tanks. Since LH2/LOX tanks were required
to be cylindrical, they could not be shaped into wings or fusilage to assist aerodynamics, and to make them
fully recoverable and reusable.

That is no longer true.

What is true is spheres hold more volume per skin area than cylinders, and cylinders hold more volume per
skin area than other shapes, but they they don't hold that much more, approximately 10% or so.

Since the conformal tanks add structural strength to the wings, and overall spaceplane fusulage, less
material needs to be used duplicating those sturctures when tanks and orbital vehicle are two or more
pieces. Whatever extra mass is used to increase the volume because it is not the least skin-to-volume shape
possible is saved ten times over by not having the spaceship strengtheners duplicated twice on both tanks
and spacecraft.



SO. We have established that vehicles can achieve LEO from ground launch Gross Weight at Liftoff of 4.5
million pounds. The Shuttle empty weight is 151,205 lb, and the max payload is: 55,250 lb.

157,143 pounds of the 1.1 million pounds of contents in the External Tank is Hydrogen, and 942,857
pounds is Oxygen.

The SRBs drop off at 150,000 feet. Their job is to provide 71% of the total thrust to get that high. A large
part of that job is carrying their own weight (2.6 million pounds at launch) and the excess weight of oxidizer
through the thickest part of the atmosphere. Instead of getting any help from the atmosphere, they fight it
every foot of the way.

You can get rid of the SRBs, saving 2.6 million pounds. The SR-71 weighed in at Maximum gross takeoff
weight: 172,000 lb (78,000 kg) versus Shuttle empty weight is 151,205 lb. The SR-71 needed more fuel to
keep thrusting, and it needed oxidizer if it was going to keep rising. Either one of them needs more wings to
take-off with 80,000 pound payload. With wings as tankage for LH2, the SRBs are not needed to loft their
own 2.6 million pounds weight and nearly 1 million pounds of LOX of the External Tank.

66,000 pounds of external tank isn't going to become 66,000 pounds of winged tanks because the bulk of
the stresses are the high speeds through the thickest air. Flying at low speeds to thin air saves lots of fuel
and reduces the stresses, so the strength can be shrunk accordingly, which reduces the weight required for
the ultimate strength. An unknown, because it cannot be computed yet, weight savings is incurred by not
carry so much LOX required by the SSMEs helping the SRBs lift 8 million pounds through the thickest soup
of the atmosphere.

At least two million pounds of fuel is expended by the Shuttle cluster to get up to the altitude that Helios got
on 28 horsepower with light wingloading. Assuming the SSMEs are consuming fuel at a constant rate from
launch to separation of the ET, the shuttle has consumed 235,711 pounds of oxidizer getting to Helios cruise
altitude where SKYLON is expecting to load up on the oxidizer. It also means that about 707,135 pounds of
oxidizer are required from here to get to LEO pushing the non-aerodynamic Shuttle Cluster. The SRBs drop
off 50,000 feet higher and the ET drops off just below the last of the atmospheric effects, 362,243 ft.

There is atmospheric effects detected at about 75 miles high on re-entry. This means there is enough air that
friction heating is occurring beginning ar this point. What it also means is air particles are ricocheting off the
spacecraft due to it's motion. These ricochets are the principle of lift in winged flight. Because there is
insufficient wings going or coming back, there is not enough surface to glide on these particles.

The ENTIRE Shuttle cluster rocket thrust occurs inside atmospheric effects. The shuttle coasts the last few
miles out of the atmosphere, and keeps on coasting to it's final orbit using a small amount of onboard fuel for
final flight adjustments.

By not having good enough wing design they struggled up and then, coming back they cannot slow the
descent on those little wings. It takes longer coming back on wings, meaning a bit longer in the hot part, but
not as hot because the speed of friction is lower, and down below is is a frigid air layer that will soon enough
cool off the vehicle if it has enough wings to fly in that layer for a bit. Active cooling requires some
cryogenic gases be retained in the craft for the ride home, another benefit of having a large payload
capacity, so that return is fully controllable fueled landing at airport of choice.