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Admiral_Ritt

Member

From: Imperial Capital of the Pacifi

Registered: 2005-03-09

Posts: 64

Re: Lightest Possible Two Man LM

For Taxing service between LUNA and it's surface.   

I have always been amazed at how small the Upper Section of the LM was
especially it's engine/fuel complex.

Here are some parameters to throw out there, to help reduce weight.

1) no pressurized crew cabin.

2) lander is pure transportation only, assume it's a taxi to lunar base.

3) Lighter Space suit modest breathing pack(8 hours only)
what was the estimate, Lunar Space suits weighed what? 200 lbs.
surely we can trim loads off of there?

4) On-orbit & Lunar re-fueling available.   That's right Fuel requirements
are reduced by 45%. 

5) Egress hatch. (looked pretty heavy on the LM)  Without a pressurized cabin, something weighing about as much as cardboard would do.

6) Computer, Avaionics,  Huge weight savings here with modern equiment.

7) Three Legs

Here are some additions that would be prudent for a regular taxi service.
1) two engine design.   Just in case
2) slight charge applied to exterior of Lander while exposed to keep Dust off.   

In my mind I come up with something that:

Weighs 45% of a LM
And is  66% it's size in Volume.

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 28,970

Re: Lightest Possible Two Man LM

Lets start with the LEM info and image.
Apollo LM

Crew Size: 2. Length: 6.37 m. Maximum Diameter: 4.27 m. Span: 9.07 m. Habitable Volume: 6.65 m3. Mass: 14,696 kg. Main Engine: TR-201. Main Engine Thrust: 4,491 kgf. Main Engine Propellants: N2O4/UDMH. Main Engine Propellants: 10,523 kg. Main Engine Isp: 311 sec. Spacecraft delta v: 4,700 m/s. Electrical System: Batteries. Electric System: 50.0 kWh.

Spacecraft Module: Apollo LM AS. Other Designations: Ascent Stage.
Crew Size: 2. Length: 3.54 m. Basic Diameter: 4.27 m. Maximum Diameter: 4.27 m. Habitable Volume: 6.65 m3. Mass: 4,547 kg. Crew mass: 144 kg. RCS Coarse No x Thrust: 16 X45kgf. RCS Propellants: N2O4/UDMH. RCS Isp: 290 sec. Main Engine Thrust: 1,588 kgf. Main Engine Propellants: N2O4/UDMH. Main Engine Propellants: 2,358 kg. Main Engine Isp: 311 sec. Spacecraft delta v: 2,220 m/s. Electrical System: Batteries. Electric System: 17.0 kWh. Battery: 800.0 Ah.

Spacecraft Module: Apollo LM DS. Other Designations: Descent Stage.
Length: 2.83 m. Basic Diameter: 4.21 m. Maximum Diameter: 9.37 m. Mass: 10,149 kg. Main Engine Thrust: 4,491 kgf. Main Engine Propellants: N2O4/UDMH. Main Engine Propellants: 8,165 kg. Main Engine Isp: 311 sec. Spacecraft delta v: 2,470 m/s. Electrical System: Batteries. Electric System: 33.0 kWh. Battery: 1,600.0 Ah.

publiusr

Banned

From: Alabama

Registered: 2005-02-24

Posts: 682

Re: Lightest Possible Two Man LM

That's about 15 tons for both the lander and orbiter.