An alternate Vision for Space Exploration
by Eric R. Hedman
|One of the biggest problems I think that the VSE has is that it requires too many important decisions to be made right now, committing to a long-term plan that may have serious flaws.|
The part of the VSE that I whole heartedly agree with is that it is the intent of the United States of America to have a human spaceflight program with the ultimate goal of human exploration of the Moon, Mars, and other bodies in our solar system. It should also be the goal of NASA to help develop the technology in partnership with industry and other nations to accomplish these goals.
Safe, cost-effective access to orbit is the first step I would worry about. I agree with others that have advocated using the Atlas 5 or Delta 4 launchers for this purpose. I know the ESAS has an argument against this, but during the studies for the Orbital Space Plane a couple of the designs were based upon using them. I don’t believe that Boeing and Lockheed Martin would have proceeded with these plans if they couldn’t reasonably think they could be used. There would have been just too much for them to lose if the plans had failed. I also do not believe that human rating these launch vehicles would be that difficult. Putting the crew capsule atop the stack with escape rockets alone would make the vehicle significantly safer than the Shuttle.
I don’t care if the crew vehicle is a capsule or a plane, though I did like Lockheed Martin’s Orbital Space Plane design. It should however have some minimum requirements. It should be able to carry a minimum of four crew members. It should be capable of staying in space for six months docked to the ISS or to a service module when used for potential lunar orbit missions. It should be compatible with both the Atlas 5 and the Delta 4, as well as possible other future launchers. Its first mission would be to ferry a crew and some cargo to and from the ISS.
I would include a plan for the ISS and its continued use. I don’t see a point in spending a hundred billion dollars on it, or even another assembly flight, if it isn’t going to be used. And I do think there are some really good uses for it. The first part of the plan I would have for the ISS is to complete it with the remaining 18 Shuttle launches. I would also start planning some changes to it beyond these flights.
The ISS needs to be moved into a better orbit. The concept of using electrodynamic tethers to move the ISS into an orbit inclined at 28.5 degrees to the equator is compelling. To enable this I would start committing funds to develop actual flight hardware. I would also try to convince Russia to move their manned Soyuz launches to ESA’s French Guiana launch site so they, too, could launch to this orbit. If the tether was attached to the ISS in 2010, it could according to the studies I have read, have the ISS in the right orbit by 2014. The two biggest advantages of having the ISS in a 28.5-degree orbit supported by the Soyuz or its successor and the shuttle’s successor are as that the ISS could be used to support trips beyond Earth orbit, and any launcher would have greater payload capability to this orbit. An electrodynamic tether can also provide reboost capability and a method to desaturate control moment gyros, significantly reducing the need carry fuel to the station for these purposes.
I would use the ISS for a number of purposes, including both a scientific research center and an engineering test bed. If humans are to fly eventually on to Mars and beyond, we do need to know if there is a solution to bone and muscle loss that result from long-term exposure to microgravity. Whatever the answer is will determine how we send people on these missions. If artificial gravity from a rotating vehicle is required it may add significant costs and delays.
|The ISS needs to be moved into a better orbit. The concept of using electrodynamic tethers to move the ISS into an orbit inclined at 28.5 degrees to the equator is compelling.|
After the station reaches “core complete” with the remaining shuttle launches I would add as a test a large inflatable module purchased from Bigelow Aerospace, provided that their upcoming scale-model orbital tests are successful. This module should have the primary purpose of testing technology for enabling long-term spaceflight. I would require it to have a sufficient diameter that it could be used test a rotating balanced two-person exercise bicycle that could provide some artificial gravity for an astronaut’s heart to pump blood against. It would be an excellent way to see if such a facility would work attached to a deep space mission vehicle for maintaining crew health. In addition, this module could be used to test all sorts of technology for use in space vehicles without risking the rest of the station. The module itself would be a great test of the durability of the structure itself. It may be a great technology for building a lunar base.
Instead of committing right now to a mission architecture to land on the Moon, I would spend more on unmanned precursor missions to find out more about the Moon and to test technology for using resources on it. In the rush to explore the solar system, we have mostly ignored our closest and possibly most important neighbor since the end of the Apollo program. The Moon may provide the bulk of the off-Earth resources we will use to explore the rest of the solar system. I wouldn’t come up with a final plan for a Moon base or select a fuel for a lander until it was known just how much water may be locked up beneath the lunar poles, and how accessible it is.
I am in favor of a strong manned and unmanned space exploration plan. How the spending is balanced between the two should depend on how both fit the overall goals of NASA. The unmanned program can also be a test bed for technology used on manned missions and support future manned missions. A lunar lander to carry robotic rovers could be a test vehicle for oxygen and methane engines and surface fuel storage before it is committed to for manned vehicles.
I am not totally convinced that the expensive heavy-lift vehicle proposed to carry the Earth Departure Stage is necessary. An alternate approach could be to develop a two-stage smaller launcher where the second stage doubles as the Earth Departure Stage. This could work if the second stage is refueled in orbit. The main reason the heavy-lift launcher has to be so big is that it has to carry the mass of the fuel for the Earth Departure Stage into orbit.
Refueling in orbit could be accomplished by building a fuel storage facility in orbit. I would have it in orbit a few kilometers behind the ISS once it had been moved to a 28.5-degree orbit. It could be tended by astronauts on the ISS if a small tug was developed to carry them back and forth from it. Smaller rockets could carry fuel up in several cheaper launches. This could be another opportunity for COTS-type procurement, increasing the market potential for the companies competing for ISS resupply. A fuel storage facility could eventually have at least its liquid oxygen supplies coming from the Moon, greatly reducing the need to lift it from Earth. The technology developed for this facility could potentially be used to develop technology for handling hydrogen for fuel cell-based cars.
|An orbital fuel depot could be another opportunity for COTS-type procurement, increasing the market potential for the companies competing for ISS resupply.|
I’m a strong believer that it would be prudent to prepare a site for the first human return to the Moon. NASA worries about the risk for their launch vehicles. They published what I consider absurd figures for the reliability of the yet-to-be-fully-designed, not-yet-built, and not-yet-flown vehicles. The first flights of the vehicles are like Apollo in that there are several segments of the mission profile where no rescue of the crew is possible. If the engine to lift off from the Moon doesn’t light when needed, what do you do? Keeping a second vehicle in Earth orbit ready to mount a rescue doesn’t sound too feasible. If a habitat is prepositioned and stocked with several months of supplies, you walk over to it and wait for the next crew.
Sending unmanned payloads to the Moon doesn’t require a quick two- or three-day trip. Sending payloads to the Moon could use and prove new technologies like solar thermal propulsion, Hall Effect thrusters, or VASIMR engines. If they take a couple of weeks or even a few months to get there, who cares?
The current vision doesn’t push the envelope on technology development. It can’t because a failure in development based on new technology could doom the whole plan. An incremental plan doesn’t have this problem. If pushing the envelope fails, you go back to a tried-and-true method and keep moving forward. If the current approach to the project had been used for aircraft development, Frank Whittle’s newfangled contraption called the jet engine would still be waiting for a better, safer, more convenient time to try it out. After all, you can build airplanes with propellers that can get to almost any place on the planet.
In my alternative a first mission to the Moon would have the following profile. It would start with a launch of the lunar lander atop a two-stage rocket smaller than the proposed heavy-lift shuttle-derived vehicle. It would arrive in orbit with its second stage still attached and dock with the fuel storage facility orbiting just behind the ISS. After the vehicle had been thoroughly checked out in orbit, the crew would launch to the ISS and wait for the empty second stage to refuel. When the stage is fully fueled and the launch window is ready, the crew would use their capsule or space plane to transfer over to the Earth departure stack and leave for lunar orbit. Upon reaching either lunar orbit or the L1 or L2 libration points (whichever is the most efficient), they would descend to a base that would already have a habitat waiting for them and large rovers that would allow for intensive exploration in the area. It may also be possible that an automated lunar oxygen production facility could re-supply the lander with some or all of the oxidizer it needs to return to the orbiting return vehicle.
I have said in the past that I do like the plans laid out in the ESAS. However, I’m beginning to have my doubts. I know there is more than one way to proceed that will work. I also know, though, that all of us will never agree as to which plan that is. Somebody has to be in a position to make the decision and press forward. There are many people out there with no interest in space exploration that prefer that we don’t move forward. People promoting NASA like to talk about how the technology spinoffs have benefited everyone. To be honest the bulk of the benefits resulted from technology developed during the early years when developing spacecraft required a hard push on the technology envelope. I would like to see us do that again. It would shift more money into R&D and less into maintaining a large workforce struggling to keep decades-old, obsolete technology working.