Author Topic: Reusable LS-LLO shuttle using Lunar LOX  (Read 3980 times)

Offline Apollo Alum

  • Member
  • Member
  • Posts: 21
  • Liked: 0
  • Likes Given: 0
Reusable LS-LLO shuttle using Lunar LOX
« on: 07/17/2007 09:11 pm »

OK, back to what I really enjoy doing. Sorry this is so long, but there's a lot of stuff here.

The Objective:

The objective is to extend the lunar capabilities of the currently-conceived next generation of launch vehicles, specifically the Ares-V HLLV. The key to this objective is to reduce the number of Earth launches required for each lunar mission from the present 1.5 launches (1 Ares-I and 1 Ares-V) to a single Ares-V launch. The real goal here is to minimize the cost of each mission, thereby making lunar missions more affordable and thereby, hopefully, more pleasing to the eyes of the Congress.

The basic assumption is that we are able to harvest lunar oxygen, either from the common regolith or from water ice at one or both poles, and use it as a propellant for a reusable LS - LLO shuttle. I will start a separate thread later to study the possibilities that open up if it turns out to be feasible to harvest both lunar hydrogen and oxygen.

Mission Profile:

  • A single HLLV launch. The stack consists of the Booster stage using 2 5-segment SRMs, the Core stage using 5 RL-68's, the extended EDS using 1 J-2X, a full LH2 propellant tank for the Lunar Shuttle, a Cargo module destined for the lunar surface, and the Lunar CEV (4-person CM plus Lunar SM).
  • The initial EDS burn delivers the payload to TLI on a direct-ascent profile.
  • The second EDS burn inserts the payload into a co-planar lunar orbit. The EDS is expended.
  • The reusable lunar shuttle leaves the lunar surface carrying its ascent propellants (LOX + LH2) plus the LOX required for the descent back to the surface. All LOX is derived from lunar resources.
  • The shuttle enters LLO and performs whatever plane-change maneuver is necessary to rendezvous with the CEV.
  • The Cargo pod and LH2 tank are transferred from the CEV to the Shuttle.  [Alternate: if it turns out to be less risky to keep the same tank on the shuttle and transfer the fuel, then so be it. It makes no difference to the mission capacity.]  The empty LH2 tank is expended.
  • Presumably the crews swap vehicles.
  • The SM does the TEI burn to return the Command Module back to Earth.
  • The shuttle does another plane-change maneuver, de-orbits, and lands back at its base.
  • The shuttle refuels with lunar LOX for its next trip.

Capacities:

The current Ares-V HLLV can deliver 65.4 metric tons (net) to TLI on a direct-ascent profile. "Current" is a moving target - I am using the version with 5 RS-68s, 2 5-segment SRBs, and an EDS with a single J-2X. As the booster evolves these numbers will change accordingly.

The direct-ascent profile delivers a higher mass to TLI than does the profile which includes a stop-over in LEO. Since this is a single-launch mission there is no EOR to carry out, so the LEO stop-over is unnecessary.

I am assuming the EDS tankage is extended to carry enough propellant for both TLI and a co-planar LOI. Adding a separate LOI stage would only marginally increase the net payload delivered to LLO and would necessitate development and crew-certification of yet another stage. I don't think it trades off well.

Insertion into a co-planar LLO requires a ΔV of 850 m/s. The mass ratio for such a burn using the EDS is 0.8247. Given a mass at LOI ignition of 89.4mT (65.4mT net + 24mT extended EDS dry mass including residual propellants), the total mass inserted into LLO is 89.4 X 0.8247 = 73.7mT.

The EDS is expended, leaving 49.7mT in LLO. This manifest is a full LH2 propellant tank for the Lunar Shuttle, a Cargo module, and the Lunar CEV (4-person CM plus Lunar SM). As currently conceived, the lunar CEV masses 20.7mT, which leaves 29mT of LH2 plus tankage plus cargo in LLO waiting for delivery.

The Lunar Shuttle

The Lunar Shuttle is a single-stage reusable vehicle designed to depart the lunar surface with a full round-trip (LS-LLO-LS) load of LOX derived in situ, reach LLO, perform the necessary plane-change burn to match the CEV stack's co-planar orbit, pick up cargo plus a full round-trip (LLO-LS-LLO) load of LH2, perform the necessary plane-change maneuver to return to its base, de-orbit, and land. The shuttle should be designed to carry a crew of five to support the mission where the same pilot flies it to LLO with a crew of 4 returning to Earth, and returns to the lunar surface with a new crew of 4.

The baseline dry mass of the shuttle is 23mT. I am assuming this vehicle is a growth product of whatever the final LSAM turns out to be and not an entirely new vehicle. So for now I used the basic LSAM structure, cabin, engines, etc, eliminating only the separate ascent stage, and scaling the propellant tanks to the required size. These are place-holder numbers only. Later optimization trade-offs will include the number, size, and placement of the LH2 tanks, especially if tanks are physically swapped in LLO.

This mission requires a ΔV of 2,400m/s each way, assuming the worst case of a base at the Aitken Basin near the South Pole. Lunar bases elsewhere have lower ΔV requirements, which require less hydrogen, and therefore allow more cargo to be lifted from Earth. Based on this, the mass ratio for each half of the trip μ = 0.58.

Propellant calculations are more complex this time because we are adding mass at each end of the trip.

At departure from the lunar surface,

M0 = Mv + Mao + Mah + Mdo

where Mah is the mass of LH2 consumed during Ascent, etc.

Upon arrival in LLO,

M1 = Mv + Mdo = μ • M0

In LLO the shuttle acquires the cargo (Mc) plus the descent hydrogen (Mdh) and ascent hydrogen (Mah). The mass at ignition to depart the co-planar orbit then is:

M2 = Mv + Mc + Mdo + Mdh + Mah

And, finally, the mass upon landing is:

M3 = Mv + Mc + Mah = μ • M2

Solving simultaneously, and assuming Mv = 23mT, we find that for Mc = 18mT, we require a LH2 load of 10.2mT in LLO, for a total payload delivered to LLO by the Ares-V of 28.2mT, just within the 29mT limit we calculated above.

Getting it There:

Given these parameters, the lunar shuttle can be built on Earth and lifted to LLO by a single HLLV launch. The total payload is the dry shuttle mass of 23mT plus 26mT of LOX, within the 49.7mT LLO capability of the Ares-V + Extended EDS. Once in LLO, a launch of the HLLV/CEV stack described earlier carries a light load of 10mT of LH2 and 14mT of cargo which the shuttle will take to the surface on its maiden voyage.

Conclusions:

Harvesting lunar LOX is a crucial step towards dramatically lowering the cost per lunar mission. The trade-off is 1 Ares-V launch to place the shuttle in LLO initially versus 1 Ares-1 launch plus the cost of an expendable LSAM per mission. If the life of the shuttle is as low as 2 or 3 LS-LLO-LS round-trips, the total program cost will benefit. If the life of the shuttle is as long as 10 or more trips, significant cost savings can be realized. Replacing short-life shuttle components, such as individual engines, either in LLO or on the lunar surface, can dramatically lengthen the useful life of each vehicle.

Ron

Been there. Done that. Got the rocks.
—•— —•—• •———— —••• ——•

Offline kraisee

  • Expert
  • Senior Member
  • *****
  • Posts: 10484
  • Liked: 419
  • Likes Given: 19
Re: Reusable LS-LLO shuttle using Lunar LOX
« Reply #1 on: 07/17/2007 09:44 pm »
I agree that harvesting Lunar LOX is one of the most critically important aspects of a far-reaching expansion of the human race out into our solar system.   It just makes too much sense not to use it, especially as you describe, for a Lunar Orbit to Surface reusable taxi.

I can't help thinking of a "DC-X"-style concept for the moon.

The only question I have is how thoroughly has the mining, processing, refinement and storage of processed minerals process been investigated so far?   I can only find very sketchy data about techniques, equipment and mass allocations for such equipment.    But to enable this architecture, this all has to be turned from theory into hard engineering.   I would love to see the results of such work.

Ross.
"The meek shall inherit the Earth -- the rest of us will go to the stars"
-Robert A. Heinlein

Offline Apollo Alum

  • Member
  • Member
  • Posts: 21
  • Liked: 0
  • Likes Given: 0
Re: Reusable LS-LLO shuttle using Lunar LOX
« Reply #2 on: 07/17/2007 10:05 pm »

Ross,

I remember reading a pretty good paper back in the early 70s or thereabouts regarding techniques for extracting Aluminum and Oxygen from the regolith. The author actually recreated the regolith samples returned by several Apollo missions and then used various techniques which were appropriate to the lunar environment (i.e. - don't require a great deal of single-use chemicals, water, etc) to extract the various materials. I remember O2 was pretty easy. Aluminum harder. Iron was really hard.

It's possible it was an internal NASA paper, but I don't think so. Be worth Googling around to see if traces of it are on-line.

Ron

Been there. Done that. Got the rocks.
—•— —•—• •———— —••• ——•

Offline kraisee

  • Expert
  • Senior Member
  • *****
  • Posts: 10484
  • Liked: 419
  • Likes Given: 19
Re: Reusable LS-LLO shuttle using Lunar LOX
« Reply #3 on: 07/17/2007 10:21 pm »
http://www.ssi.org/ has some good resources, but most of the techniques do not appear to be deep enough to me.

I like the idea of the conveyor system of separating out regolith using multiple heating elements, each "evaporating" off different minerals at different locations down the conveyor line by exposing the regolith to different temperatures.

Not sure how practical it would actually be (size, weight and speed of processing) but, as a simple concept, it seems to be a reasonably effective solution to consider.

Ross.
"The meek shall inherit the Earth -- the rest of us will go to the stars"
-Robert A. Heinlein

Offline wingod

  • Full Member
  • ****
  • Posts: 1305
  • Liked: 0
  • Likes Given: 0
Re: Reusable LS-LLO shuttle using Lunar LOX
« Reply #4 on: 07/17/2007 11:16 pm »
Quote
kraisee - 17/7/2007  5:21 PM

http://www.ssi.org/ has some good resources, but most of the techniques do not appear to be deep enough to me.

I like the idea of the conveyor system of separating out regolith using multiple heating elements, each "evaporating" off different minerals at different locations down the conveyor line by exposing the regolith to different temperatures.

Not sure how practical it would actually be (size, weight and speed of processing) but, as a simple concept, it seems to be a reasonably effective solution to consider.

Ross.

For a good overview do a google on NASA SP-509 or download it from the NASA NTRS server.  



Offline neviden

  • Regular
  • Full Member
  • ****
  • Posts: 411
  • Liked: 1
  • Likes Given: 0
Re: Reusable LS-LLO shuttle using Lunar LOX
« Reply #5 on: 07/19/2007 09:48 pm »
This looks like a nice plan. But I do have few questions. Have you looked at any other orbit other than LLO? How about 200 x 10000? How about L1/L2? How about rendezvous in HEEO?

It should have lower delta-v to get from LEO therefore it could have more hydrogen/payload left onboard. You would of course need more delta-v to get from LS, but since most of the propellant would be lunar oxygen (“cheap”), would this increase the capabilities to LS?

Offline Apollo Alum

  • Member
  • Member
  • Posts: 21
  • Liked: 0
  • Likes Given: 0
Re: Reusable LS-LLO shuttle using Lunar LOX
« Reply #6 on: 07/20/2007 12:58 pm »

Neviden,

You raise a very interesting question of optimization. Where is the transfer point between a ES-TP-ES vehicle and a LS-TP-LS shuttle that maximizes the amount of cargo deliverable to the LS using one CaLV launch?

Check out my other thread in this forum on Lunar Oxygen + Earth Hydrogen. It turns out the farther away from LLO you get the more LH2 you have to carry up from Earth. If you go to the other extreme, LS-LEO-LS using lunar LOX plus LH2 lifted from Earth, it is impossible. You can't build a bird big enough.

Is there a saddle point? I don't know. I haven't run the numbers for HELO, Lx, or HEEO. I'll let my simulator play with the idea when I have a chance.

Thanks for the idea.

Ron

Been there. Done that. Got the rocks.
—•— —•—• •———— —••• ——•

Offline neviden

  • Regular
  • Full Member
  • ****
  • Posts: 411
  • Liked: 1
  • Likes Given: 0
Re: Reusable LS-LLO shuttle using Lunar LOX
« Reply #7 on: 07/20/2007 02:19 pm »
Direct-ascent from Earth to TLI has the lowest delta-v. Direct-ascent from Moon to TEI has lowest delta-v. Since TLI and TEI is basically the same thing (highly elliptical earth orbit), is it the saddle point? If not HEEO, which other orbit? 2:1 resonant orbit? Halo around L2? LLO?

HEEO would save few insertion burns (less delta-v) plus you could catch lunar lander few hours after the launch from earth (when it would be at HEEO perigee). But it has it's own problems like Van Allen radiation belt and the fact that everything moves around..

Tags: