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Oct 18, 2015

LEAMOR Manned Space Craft - Modular Transport Engine (Part 3)

PART 3: Modular Transport Engine (TE)

LEAMOR stabnds for Light Extended Apollo Mars Orbit Rendezvous.

As we already have figured out that the large spacecraft must be modular (since the lift vehicle can only lift a certain amount to the LEO at one time). See the previous part of this article series and we call these about 150 ton (lbs) building blocks as L-modules.

L-Modules about 150 000 lbs each, size about D5 x L11.75

Using L-modules we can now bolt together our required spacecraft in LEO. The L-modules are constructed so that as much as possible of the work is done on the Earth and that a single module just adds fuel with as little as possible extra weight to any spacecraft version. The following picture shows two space craft TE versions. Lets call them TE(3+1+L) and TE(7+1+L).

Different spacecraft Transport Engines (called TE a+b+L) can be built using L-modules. Here we see the TE (3+1+L) and the TE (7+1+L) versions. Any TE (a+b+L) could be built. L is usually 150 tons but could be something else also.

TE(7+1+L) simply means that the first stage is about 7 modules and the second is about 1 module. When using to our Mars journey it means that about 7 modules of propellant is used for the Trans Mars Injection (TMI) burn and that 1 is left for the Mars Orbit Insertion (MOI) burn.

Notice that also any fractions of the sizes could be used if required, for example TE 7.5 + 1.5 + L. Also partially filled propellant tanks could be used to achieve any desired exact propellant amount.

Typical delta-V values. For Mars for example TMI = 3.8 km/s, MOI = 2.3 km/s (Mars Landing 4.1 + 4.1 km/s)

[About the aerobraking (AB): The LEAMOR concept does not primarily use any aerobraking so it is good to any planet or the Earth's moon. But since the MV propellant balls are large they could be covered with some material and assist in the descent. Calculations are done without any aerobraking to Mars. The re-entry to the Earth uses Orion capsule (or similar) and so always uses aerobraking.]

Also the following NASA studies show similar delta-V requirements for Mars missions.

Long Stay Mission (LSM) delta-V requirements.

Short Stay Mission (SSM) delta-V requirements.

The above figures shows that a typical Mars mission might need propellants as follows:
  • TMI about 4 km/s
  • MOI about 2 km/s
  • TEI about 4 km/s
Since our spacecraft's L, or the load required by the transport engine to be pushed, is about 150 tons, we can now calculate some delta-V values for our total spacecraft:

TE Version All full
[t lbs]
dry 1
[t lbs]
Full 2
[t lbs]
dry 2
[t lbs]
3+1+L 750 340 320 180 2.41 1.75
7+1+L 1350 380 320 180 3.87 1.75
8+1+L 1500 390 330 190 4.11 1.68
7.5+1.5+L 1500 460 400 190 3.60 2.27

Here is as an example weights calculation for the TE (3+1+L) version, we assume that a propellant only module is 140 tons propellants plus 10 tons dry weight and a rocket module is 130 tons propellants plus 20 tons dry weight.

1st burn (TMI)

  • full = 150 + 150 + 3 x 150 = 750
  • dry = 150 + 150 + 2 x 10 + 20 = 340

trop 2 empty modules - 20 = 320

2nd burn (MOI)

  • full = 320
  • dry = 150 + 10 + 20 = 180

The last row TE (7.5+1.5+L) id done by shifting ½ L-module from TMI burn to MOI burn. The size of a L-module (excluding structure) is about 140 tons and that is divided by 2 to get 70 tons. For our Mars mission the last 3 rows seem to give the most usual versions for TMI (about 4 km/s) and MOI (about 2 km/s).

To put our astronauts to the Mars (and back) we need 3 x TE(7+1+L) transport engines and the Mars Vehicle (MV, nominal 150 tons), Entry Vehicle (EV, nominal 150 tons) and Return Vehicle (RV, nominal 150 tons). The following picture shows now these required parts of the full mission.

LEAMOR full mission using TE(7+1+L)s: 1st send MV and the cross tube, 2nd send the RV and finally the EV with astronauts.

The full voyage with the above configuration to the low Mars orbit (LMO) is about 7+ months. The RV and EV both include the Habitat Module (HM) which they are pushing. Both EV and RV are return capable so that there are 2 fully operational vehicles when astronauts arrive to the LMO. If something happens to one spacecraft hopefully the other can still be used and the men returned safety to the Earth. If the MV is not operational then the landing will not be done. Typical Apollo style abort options can be maintained for safety of the astronauts.

LEAMOR parts in Mars Orbit (LMO)

Sending only 3 astronauts requires less consumables. The habitat module can include a small gravity wheel so that the astronauts can run inside it so that the long stay in space would not produce any bone loss problems etc.

LEAMOR docked together in LMO

The MV is too large to be lifted in one piece to the LEO so it must be disassembled before sending as the following picture shows and then assembled again in the low Earth orbit.

Left: Mars Vehicle (MV) disassembled and ready to be launched from Earth's surface to the LEO. It requires a special upper stage. Only the fuels balls and the landing gears need to be bolted together in LEO. Right: assembled MV.

And so the big question is: "How many full SLS (or similar) launches would that mission require?"  - if the SLS can lift up to 300 tons (lbs), then only maybe 12 .. but more if it lifts less at a time. The amount of lifts to the LEO is proportional to the weight of material to be sent to the Mars. Some material could be sent using direct robots which would not use the LEO or LMO etc.

(The next part of this article will cover the EV and RV in more detail.)


/1/ Wikipedia

/2/ NASA

/3/ Apollo archives

/4/ YouTube

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