Darpa Revives Larger Reusable Booster Spaceplane

On Saturday, October 12, 2013 6:10:53 PM UTC+13, William Mook wrote:
http://arc.aiaa.org/doi/abs/10.2514/6.1968-618



http://arc.aiaa.org/doi/abs/10.2514/3.30138



In the 1960s we achieved 5,224 m/sec exhaust speeds with chemical rockets..



Basically, you take nanoparticles of fluorine ice along with nanoparticles of lithium and suspend them in a super-cooled mixture of liquid hydrogen.



F -219.6 C mp 1.505 g/cc 0.55

H2 -252.9 C bp 0.070 g/cc 0.25

Li +180.5 C mp 0.535 g/cc 0.20



Overall density of 0.232 g/cc



To attain the same performance as the Space Shuttle requires a vehicle achieve a delta vee of 9,200 m/sec. A single stage vehicle with a 5,224 m/sec exhaust velocity requires a propellant fraction of;



u = 1 - 1/exp(9200/5224) = 0.82814



Now, consider a Super Light Weight Tank for the Space Shuttle:



SLWT Specifications



Length: 153.8 ft (46.9 m)

Diameter: 27.6 ft (8.4 m)

Empty Weight: 58,500 lb (26,500 kg)

Gross Liftoff Weight: 1,680,000 lb (760,000 kg)



LOX tank



Length: 54.6 ft (16.6 m)

Diameter: 27.6 ft (8.4 m)

Volume (at 22 psig): 19,541.66 cu ft (146,181.8 US gal; 553,358 l)

LOX mass (at 22 psig): 1,387,457 lb (629,340 kg)

Operation Pressu 20-22 psi (140-150 kPa) (gauge)



Intertank



Length: 22.6 ft (6.9 m)

Diameter: 27.6 ft (8.4 m)



LH2 tank



Length: 97.0 ft (29.6 m)

Diameter: 27.6 ft (8.4 m)

Volume (at 29.3 psig): 52,881.61 cu ft (395,581.9 US gal; 1,497,440 l)

LH2 mass (at 29.3 psig): 234,265 lb (106,261 kg)

Operation Pressu 32-34 psi (220-230 kPa) (absolute)

Operation Temperatu -423 °F (-252.8 °C)[9]





It has a LH2 tank with 1,497,440 l capability and a LOX tank with 553,358 l capability. A total of 2,050,798 l. At 232 grams per liter this has a total capacity of 475,785 kg. Dividing this by u we have a Take off Weight of;



TOW = 475,785 / 0.82814 = 574,519 kg.



Subtracting off the propellant and structure we have;



payload = 574,519 - 475,785 - 26,500 = 72,234 kg



Less any additional structure required - e.g. - engine, avionics, etc., plus any savings or removals (intertank, cross-feed, support structure, etc.)



A payload of 72,234 kg in LEO requires only 7,750 m/sec delta vee to go to the moon, land, and return to Earth;



2,950 m/sec LEO to TLI

2,400 m/sec TLI to Lunar Surface

2,400 m/sec Lunar Surface to Trans-Earth Injection



7,750 m/sec TOTAL delta vee.



So, the propellant fraction here is;



u = 1 - 1/exp(7750/5224) = 0.773166



So, with a total weight on orbit of 72,234 kg we have a need for



propellant = 72,234 * 0.773166 = 55,849 kg



at 232 grams per liter we have a volume of 240,729 liters. Only 0.117383 x the size of the External Tank. This means an miniature external tank only



(0.117383)^(1/3) = 0.48963



times the size of the original, will achieve this.



Length: 75.3 ft 23.0 m

Diameter 13.5 ft 4.1 m

Empty: 3,110 kg





So, a payload to the moon and back would be;



payload = 72,234 - 55,849 - 3,110 = 13,275 kg



Now, if we take the propellant mass, and divide it by the propellant fraction needed to attain orbit, we can calculate the payload (if any) this second stage could carry to orbit;



TOW = 55,849 / 0.82814 = 67,439



payload = 67,439 - 55,849 - 3,110 = 8,480 kg



So, we can see that we can build a smaller vehicle capable of putting 8.4 tonnes (18,656 lbs) into LEO and later, a larger vehicle of the same design capable of putting up 72.2 tonnes into LEO, that carries a second stage capable of placing 13.2 tonnes (29,195 lbs) on the moon and returning it to Earth.



The larger SSTO could put up a 1 giga-watt solar power satellite 815 meters in diameter that uses solar powered ion engines for attitude control and to boost from LEO to GEO. The satellite beams 10 MW to 100 ground stations on Earth simultaneously. At $0.11 per kWh the satellite earns $964.26 millions per year. Over a 30 year period the satellite earns $28.9 billions and on the day it begins earning revenue it has a net present value of $12.6 billions. Preselling 100 thirty year energy contracts to 100 buyers in Japan for 10 MW power receivers at a 20% discount over five year construction period obtains $5.1 billions per satellite. Preselling three hundred ground stations for $51 million each obtains sufficient revenues to build the launch system described a fleet of three rockets as well as a supply chain for the launcher and satellite production. Selling five 1 GW satellites per year earns $63 billions per year - more than all the space programs in the world combined. This provides revenue to



(1) send astronauts to the moon and mars, and build up capabilities there

(2) launch a network of satellites to provide a global wireless hotspot

(a) earn revenues from communications,

(b) internet services,

(c) banking and mediation services,

(d) telepresence,

(e) telerobotics

(3) use additional revenues to expand launcher system and powersatellite size

Reducing the size of the ET shaped SSTO vehicle to 1% (by weight) of the ET, we reduce the payload to orbit to 722 kg. At 144 kg per astronaut this allows 5 people to fly to orbit in a biosuit with MEMS life support, and stay there for up to 12 days. The vehicle is only 34 ft long and 6 ft in diameter. With an intertank that consists of a cylinder 4.5 ft tall and 6 ft in diameter we have five acceleration couches facing outward in the intertank region separated by 72 degrees. The tank itself has a mass budget of 265 kg!! Amazingly this is possible to achieve with advanced composites on this scale. Take off weight is only 5,745 kg.

An oblate sphere with a vertical axis 7 ft, width of 15 ft and length of 23 ft contains sufficient propellant. With MEMS based propulsive skin elements that provide for VTOL as well as horizontal flight in the atmosphere whilst maintaining very low structure fractions with advanced composites.

http://home.comcast.net/~compositex/compositex.htm