USA to return to Moon

The External Tank sized flight system, using LOX/LNG combination, with aerospike, thermal protection system, and recovery hardware attached... similar to a Falcon-R booster. Looking first at the Space Shuttle External Tank:

Technical specifications
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)

So, the LOX tank is 553.4 cubic meters. The LH2 tank is 1,497.5 cubic meters. The intertank is 382.4 cubic meters. A total of 2,413.3 cubic meters. A common bulkhead between LOX and LNG makes the extra volume available for propellant. At 830 kg/m3 the total propellant weight is 2,003,039 kg. 527,115.6 kg of LNG aft of the bulkhead and 1,475,923.4 kg of LOX forward of the bulkhead.

Total mass of the tank is less than the SWLT figures becuase
a) LNG is less difficult to keep cool than LH2,
b) common bulkhead between tanks is lighter than two separate tanks with intertank.

Conservatively let's keep the 26,500 kg for the tank mass.

A Raptor LOX/LNG engine produces 230,000 kgf of thrust and has a 3.6 km/sec exhaust speed in vacuum. 14 of these engines produce 3,220,000 kgf thrust with a 3.4 km/sec exhaust speed at sea level, when arranged around an aerospike engine at the base of the External Tank.

The weight of this arrangement is 26,850 kg. Another 21,700 kg of mass is used for the recovery system and landing gear. A total of 75,000 kg of inert mass per element.

Take off Weight: 2,078,039 kg
Empty Weight: 75,000 kg
Thrust Max: 3,220,000 kgf
Exhaust (sl) 3,400 m/sec
Exhaust (vac) 3,600 m/sec


Vf = 3,500 * LN( 2,078,039 / 75,000 ) = 11,625.9 m/sec

It can lift 80,830 kg into LEO as a SSTO.

Three tanks operated in two stages, with the two outboard tanks feeding the central set of engines during boost, and then falling away, to be recovered down range, are capable of lifting 391,000 kg into LEO.

Tanking an external tank of the size just described, and removing 25,000 kg of engines and insulation, reduces mass to 50,000 kg. Carrying 274,247.4 kg of propellant in a small set of tanks at its base, the tank becomes a version of Skylab - only larger. It is capable of carrying 66,752.6 kg of payload to low lunar orbit and back.

As a cruise ship, each person masses an average of 80 kg, and has another 60 kg allocated to them. A total of 140 kg. Another 619.2 kg of propellant to power rocket belts, provide the ability to take 88 people to the moon and back, and allow them to visit three spots anywhere on the lunar surface!

http://rocketbelt.nl/pogos/nasa-lunar-transport

https://airandspace.si.edu/research/...inding_Aid.pdf

The recurring cost, with reusable ships and propellant costs of $0.16 per kg, is around $15,000 per person. The flight could be filled at $515,000 per person, earning $44 million per month.