Just another Apollo? Part one
The nuts and bolts: from specific impulse to RL10 derivatives
While the ESAS resembles Apollo superficially, both in mode of travel to the Moon and back and in the shape of the spacecraft, real missions will be entirely different from Apollo. Twice the number of crew will land anywhere on the lunar surface, for months instead of days, and with tons of scientific equipment instead of kilograms. The mission architectures are similar, but these are dictated by the laws of physics and orbital mechanics. How closely do the CEV and LSAM resemble the Apollo CSM and LM?
The CEV is an Apollo-like capsule that includes a crew module and a service module, just as did the Apollo CSM. However, the exterior appearance is where the similarities abruptly end. The CEV’s crew module will have three times the volume of the Apollo CM, and will use modern-day electronics, computers, avionics, and flight-control systems and technologies. The CEV can carry from four to six crewmembers in relative comfort; even when the CEV is carrying six crewmembers, each crewmember will have 50% more space than their Apollo predecessors did when they flew with crews of only three. While the CEV is not nearly as spacious as the shuttle, the Apollo spacecraft were certainly adequate for trips to the Moon and back; clearly the larger CEV will be just as suitable for such trips, or even more so. The CEV will include a liquid methane/liquid oxygen engine- as opposed to the Apollo hypergolic SPS engine fueled with the extremely toxic substances hydrazine and nitrogen tetroxide—and the CEV will use the benign substances of oxygen and ethanol in its RCS thrusters instead of the CSM’s hydrazine/nitrogen tetroxide mix. The CEV engine will have a better efficiency than that of the old SPS, with a specific impulse (Isp) of 362 seconds, compared to 314 seconds for the SPS (more seconds of specific impulse mean a better fuel efficiency for a rocket engine). The CEV RCS systems will also have a higher Isp than the CSM RCS.
In addition to these significant technological advancements, the CEV will also feature long-term durability in space. The Apollo CSM was powered by fuel cells and could function in space for about two weeks autonomously or, at its maximum demonstrated endurance, 84 days when docked to a space station. The CEV will instead be powered by two solar panels connected to the service module, and will be able to be in space for up to six months without a crew. In addition, the solar panels will generate about 40 percent more power than the Apollo fuel cells did. This will allow the CEV to function as an ISS Crew Return Vehicle (CRV), when it comes online in 2011–2012, and later to stay in lunar orbit unattended for months to allow large crews to operate on the lunar surface for long periods of time. The Apollo spacecraft could not function in lunar orbit unattended at all.
Like Apollo, the CEV will jettison its service module at reentry and enter the atmosphere only with the crew module, but the CEV will land on land rather than on water, allowing the possibility of reuse and saving money by not requiring a carrier group every time a spacecraft lands. So while the CEV might very closely resemble the Apollo spacecraft visually, it is larger, capable of carrying bigger crews for longer periods of time than the Apollo, is more comfortable for those crews, far more technologically advanced, has more efficient storable propulsion systems, generates more power from an unlimited source, can function autonomously for far longer periods of time than did Apollo, and may be reusable to boot. NASA envisions using three versions, or blocks, of the CEV. The first version, Block 1, will start flying in 2011–2012, carrying crews of three to the ISS and back. The second version, Block 2, will carry crews of four to the Moon. Block 3 CEVs will support future Mars missions and will carry a crew of six.
The CEV is related to Apollo in shape only, which, as Griffin also pointed out, is dictated by physics, not politics. In reality, it is like Apollo only in the sense that a modern Corvette might resemble a 1960s Corvette. They look similar, and they do the same thing for a similar cost, inflation-adjusted. Does that mean we shouldn’t build the modern Corvettes? Should we just buy old ones, or worse, should we just stare wistfully at photos of old ones saying we don’t have the money for a new one?
The second new spacecraft is the LSAM. The LSAM is the ESAS’s version of the LM, and like the LM, has a descent stage, an ascent stage, and four legs. Once again, the similarities end there at the basic exterior shape, and in this case the differences are even greater than those between the CEV and the CSM. The LM could nominally support two men on the lunar surface for three days. The LSAM will be able to sustain a crew of four on the surface for periods of time ranging from four days to several months. The LSAM can comfortably house four astronauts on the lunar surface while the CEV orbits above, unoccupied. At this early stage, ideas call for the LSAM to carry two lunar rovers, so that the lunar surface teams can explore in two teams of two simultaneously. The LSAM will also include an airlock to keep the cabin free of pervasive lunar dust. The descent stage of the LSAM will be powered by a throttleable hydrogen/oxygen derivative of the venerable RL10 workhorse rocket engine, which will provide enough delta-v to allow the LSAM to land anywhere on the Moon (Apollo LMs could only land in the equatorial regions of the Moon’s near side). The LSAM’s ascent stage will be powered by the same storable-propellant methane engine as the CEV’s service module engine – a strategy that will save money by using a common engine.
OK, so the LSAM can support bigger crews at more locations on the moon than the LM. So what? The answer: The truly exciting thing about the LSAM is its payload capability to the lunar surface. Even in its most basic version, the LSAM can carry an astounding 2.2 metric tons of equipment to the lunar surface—about 10 times the mass of the Apollo lunar rover and all the Apollo scientific equipment put together. In a dedicated cargo mode, the LSAM can carry an astonishing 21 tons to the lunar surface—greater than the mass of the entire fuelled Apollo lunar module.
Clearly such a payload capability will easily lend itself to building a lunar outpost, as many tons of equipment can be brought to the Moon relatively easily, whether it consists of consumables, power equipment, or science tools. An initial base could be deployed by linking together several cargo and crew LSAMs; a huge amount of equipment can be brought to the lunar surface by just a few of them. In its initial missions, the extra payload capability can be used to take extra science equipment to the surface, or more consumables to allow the crew to spend long periods of time exploring the lunar surface. Once again we see that the similarities between the LSAM and LM run only skin-deep. The LM could land two astronauts on the equatorial near side of the Moon and support them for about three days. The LSAM will be able to land four astronauts anywhere on the Moon, and will support six months of lunar exploration with several tons of scientific equipment. The LSAM will have modern technology, will support crews in relative comfort, and will carry orders of magnitude more scientific equipment to the lunar surface than did the LM. The LSAM is far more suitable for supporting real long-term manned lunar exploration than the Apollo LM was. The LSAM is no LM. A long-term six-month mission with an LSAM and a crew of four could be accomplished a few years after the initial landings scheduled for 2018. Such a mission—one single mission—could enable more than 30 times the number of crew-hours on the lunar surface of the entire Apollo program, which was achieved with six heavy-lift Saturn 5s, 18 astronauts, and 12 spacecraft, over three years.
As we said, the LSAM is no LM.
The chief technical disadvantage of this plan as compared to Apollo is that two launches are required instead of one; if one fails or if the crew launch is delayed, the mission is over. This point has received a lot of attention in the aerospace community. The notion of the mission being a failure due to a booster problem is not really a fair comparison as an Apollo mission would have ended if its booster had failed as well. Some have said that requiring a crew launch within 30 days of the cargo launch (to prevent the cryogenic propellants in the EDS and LSAM from boiling off) will create dangerous schedule pressures, recreating the bad “safety culture” that led to the Columbia and Challenger accidents. However, there is a simple solution to this problem; the mission can simply revolve around the launch time of the crew launch vehicle. The HLV would not be launched until the crew is on the launch pad and their vehicle is ready to fly; this way the crew can rendezvous with the HLV only hours after launch. There is no reason to launch the HLV weeks before the crew is ready to fly. This way, no schedule pressures are created. In fact, the same thing was done during the Gemini program, when Atlas-Agena rockets were launched within hours of the Gemini-Titans carrying crews who would then rendezvous and dock with the Agenas in Earth orbit. It may be less convenient to deal with two launches, but it allows a greater payload to travel to the Moon.
Back to the future?
In the technical sense, is the ESAS “Apollo on steroids”? Yes, in the sense that no radically new technologies are being developed; we’re not flying to the Moon in gigantic interplanetary cruisers with nuclear-electric propulsion that will rendezvous at a 10,000 ton space station at the L1 Lagrange point and dock there with enormous reusable nuclear thermal propulsion stages that will have been fueled by a Delta 21 EELV derivative that will have itself been refueled by a huge interstellar ramjet mounted on a Borg cube that will be supported by Q who is helping us by mining zero-point energy from the space-time continuum (and, of course, the Q continuum). Because of this lack of totally new technology, many have attacked the plan as being too dated, despite all the differences mentioned above. These individuals would like to see very different technology before we return to the Moon—perhaps not as radical as the development of a Borg cube, but there are those who would have us wait for SSTO vehicles, solar-electric ion propulsion, or other such immature technologies before we return to the moon. (Though if a Borg cube were available for lunar transport, this author admits that such a spacecraft would provide significant advantages over the ESAS spacecraft in terms of size and speed). Unfortunately, this strategy of waiting for major technology breakthroughs—or betting on them to allow us to return to the Moon—has never worked, as witnessed by NASA’s famously colossal failures such as the X-33, X-34, X-38, or Space Launch Initiative. No, the best way to return to the Moon is using known technology—vastly improved, yes, but not out of the realm of experience of aerospace engineers. It may not be the best way to return to the Moon, and it may not be everybody’s favorite way, but few in the aerospace community deny that it will work if adequately funded.