Add private sector fuel depots (as Griffin recently called for) and it starts looking like ESAS was designed to be capable of this transition

=IF=

alt-space can deliver safe low cost Earth-to-LEO crew and cargo.

= = =

NASA builds a re-useable LEO to LLO stage and a re-useable LLO to lunar surface stage and says to alt-space, get to LEO cheaply and safely and you got yourself a contract.

Exactly.

Even if an HL-20 or t/Space CVX is used to ferry crew to/from LEO, the LEO to/from Moon stage should be able to return to Earth in case of an emergency. CEV can do that.

Once the architecture is rolling, we would launch CEV intended for numerous round trips between LEO and the Moon without landing on Earth, except in an emergency, whihjc is why CEV must be capable of doing it all.

Propulsion? Supply LH2 or methane from Earth (loaded in LEO) and LOX from the moon (loaded in lunar orbit).

Hmmm, don’t we already have a specialized Earth to Low Earth Orbit manned craft, one that is big enough to carry an Apollo capsule inside its cargo bay? Yes, I think they call it … the Space Shuttle.

Yup. And it brings far too much dead weight up and down at too high a price. Once mass is lifted to LEO, re-use that mass as much as possible and bring as little as possible back to Earth.

A tiny re-furbishable SpaceDev HL-20 or t/Space CVX can ferry crew for a tiny, tiny fraction of the cost of flying orbiter.

= = =

Note, even with a shiny alt-space SSTO RLV, we still need something like CEV for the LEO-to-Moon and return mission. Adding the shields needed to handle Earth return from Luna or Mars would make that spaceplane pretty darn heavy.

ESAS, as proposed today, can transition to this hypothetical architecture will little difficulty.

Launch a small handful of CEVs and leave ‘em up there, accessed by t/Space and SpaceDev and whoever else can do the job.

Please tell me about these additional modules. Are any of them propulsion modules which can propel the cluster of modules along a non-Hohmann planetary intercept course?

Is the concept of “modular” spacecraft so difficult for you?

Expect 4-6 people to spend 8-10 months each way between the two planets inside such a small, claustrophobic space? Not likely. Besides, where will the spacecraft carry the necessary supplies and consumables for such a long voyage?

The CEV ain’t gonna cut it for Mars travel.

Neither is travel to Mars and back along minimum energy, Hohmann paths acceptable. We’ll need a propulsion system that can make the trip between Earth and Mars in closer to ten weeks than ten months. We’ll probably need fission/thermal rockets, and beacoup H2 propellant for same — maybe more H2 than is practical to launch from Earth.

No way is the proposed CEV and conventional rocket system adequate for Mars travel.

Sincerely,

Robert Zubrin
President, Mars Society

The new capsule will not be very safe, since it seems to lack reserve parachutes, a crew ejection pod, or ejection seats for emergencies that may occur during the descent of the capsule into Earth’s atmosphere.

Furthermore, the proposed lunar launch design requires Earth orbit rendezvous of two missile launches, thereby increasing probability of mission failure compared to the Saturn/Apollo mission architecture.

That letter fails to mention the other missile entirely. That is the missile that will use a single Solid Rocket Booster as a first stage to launch the crew capsule. These Solid Rocket Boosters are unsafe, since they canot be throttled off once lit.

Dr. Zubrin, does the Mars Society accept donations from ATK Thiokal Corporation?

Why do we need another space station?

An HL-20 that did not need the heat shields capable of handling return from the moon velocities would be cheaper and lighter to launch.

Lighter and cheaper to launch than what?

A bigger robust CEV can do its lunar return by aerobraking / areocapture

I assume that sentence means aerobraking to acquire Earth orbit, and not to slow down enough to land?

No, Bill, that is simply factually wrong as a matter of engineering. As an emergency, back-up flight modality, any manned spacecraft re-entering Earth’s atmosphere would have to be able to survive descent to low altitude.

It is a very bad, unsafe idea to propose a manned trans-lunar craft that would aerobrake to gain Earth orbit, but would have insuffficient thermal protection to survive re-entry and descent to low Earth altitude.

Thinking about super-circular re-entry schemes? Designs calling for skip glide re-entry, with periods of aerobraking alternating with climbs back outside the atmosphere to allow the spacecraft to cool are impractical. Trying to skip glide with a capsule spacecraft would be especially impractical.

… and then await a t/Space or HL-20 to ferry the crew down. Use private sector tankers to refuel a propulsion stage and send a new crew via t/Space or HL-20 and go back to the moon.

Two spacecraft, one for Earth to LEO and back, the other to travel between LEO and lunar orbit, with only infrequent returns to Earth? That is a possibility, Hmmm, don’t we already have a specialized Earth to Low Earth Orbit manned craft, one that is big enough to carry an Apollo capsule inside its cargo bay? Yes, I think they call it … the Space Shuttle.

Umm, just out of curiosity, how would one do that? Physically destroy the three remaining Shuttles? Get Congress to pass a Consitutional amendment banning Shuttle operations?

Lay off about 20 thousand people.

=OR=

Design CEV to be able to remain on-orbit for years and ferry crew to/from CEV with t/Space or SpaceDev.

An HL-20 that did not need the heat shields capable of handling return from the moon velocities would be cheaper and lighter to launch.

A bigger robust CEV can do its lunar return by aerobraking / areocapture and then await a t/Space or HL-20 to ferry the crew down. Use private sector tankers to refuel a propulsion stage and send a new crew via t/Space or HL-20 and go back to the moon.