When U.S. President Barack Obama spoke to Florida space workers to reveal his plan for America’s future in space, he called for development of an “advanced” heavy-lift launch vehicle. This signaled a challenge to NASA to embrace a new paradigm for launch vehicle design, capitalizing on everything that has been learned in the previous 60 years. No more massaging of old designs. No more wishful reversions to Saturn 5 or other relic rockets. “Advanced” heavy-lifter means something new — new in design, new in manufacturing processes, new in operations.
It seems appropriate to address several issues and opportunities that are certain to shape an emerging course of events. Building a heavy-lift rocket is a serious undertaking. Engineering should be based on at least one firm mission, and reflect keen insight into the ability to perform an array of other missions, for at least the next 50 years.
- A heavy-lift vehicle will allow America to do big things in space. The Apollo program demonstrated it. A heavy-lifter was needed to get humans to the Moon. However, most of America’s achievements in space were launched by rockets limited to payloads weighing less than 25,000 kilograms to low Earth orbit. Yes, we built one big thing, the international space station (ISS), but at tremendous cost and with a prolonged build schedule. Piecemeal construction of spacecraft can cost dearly.
Although there has been much discussion regarding a return to the Moon and a manned Mars journey, there has been nothing comparable to President John F. Kennedy’s solid commitment to send men to the Moon in the ’60s. A firm mission can be readily identified, and it turns out to be neither of the above. The key lies in realization that end of life for the ISS is just a few years from now. No one is proposing a replacement, and it is doubtful that another ISS will be built. If we wait until the day it is shut down without doing anything, it is certain there will be a many-year hiatus before Americans work in space again.
Fortunately, NASA already pointed the way for the future in the 1970s post-Apollo project, the Skylab orbital workshop. Though beset with loss of insulation, loss of half its power source and other problems, the mission was a resounding success for what was deemed at the time as somewhat of a shoestring operation. Astronauts occupied the station in three stays of 28, 59 and 84 days. The Skylab experience taught that modest-size, turnkey space stations are the wave of the future.
Planning should begin now to orbit the first one soon after the ISS is out of business, ensuring a seamless transition into a new way of operation in space. Turnkey stations can fulfill manifold purposes, covering research, manufacturing and even tourist hotels. This can be big business for the U.S. space industry, providing for station needs of many nations and attending to their servicing over their respective duty cycles. Turnkey stations will weigh between 75 and 100 tons. This defines the primary mission for a heavy lifter and establishes its size.
- In light of current international concerns regarding climate change and degradation of the environment due to human activity, NASA and the Department of Defense (DoD) should be in the forefront of converting their energy consumers to green sources. DoD is already taking steps in this direction, experimenting with and promoting the use of biofuels for powering aircraft.
In rocketry, perchlorates, long used in solid rocket motors and resulting in disposal of the chemical during processing, have entered ground water and are widely dispersed, impossible to reverse. Perchlorates are suspected carcinogens, although human susceptibility is as yet undetermined. But arguments for continued proliferation of the chemical are weak, considering that clean-burning, better-performing propellants are available. Future designs by NASA should ban the use of such chemicals. NASA’s tentative plan for heavy-lifters involves development of a million-pound-thrust, kerosene-fueled engine. This foretells the transfer of huge tonnages of carbon dioxide to the upper atmosphere. Except for violent volcanoes, there are no natural processes that do this. It is not known whether it will be harmful, but it must be considered a consequential event and avoided if possible. There is an alternative — hydrogen-fueled engines, which release only water.
- For a future heavy-lifter, fueled by liquid hydrogen, the cost of development of a rocket engine would be virtually eliminated. Suitable engines, new by any measure, are already available in the Pratt & Whitney Rocketdyne RS-68 and RS-68A. The RS-68 has been employed on only a few flights on the rocket. The RS-68A, a better performer, is far along in development. Rather than undertake development of a new high-thrust engine, work should continue on succeeding generations of this engine, following the excellent progression that has taken place with the hydrogen-fueled RL10 engine over many years.
- It will be difficult to achieve meaningful cost savings with clustered, multistage designs. There is little about such configurations that can be considered “advanced,” should NASA insist on following this approach. The new paradigm should act on the realization that multiple stages involve multiple management structures, multiple industrial entities, multiple support services, etc. Each can do some things to reduce cost, but the composite result will be disappointing. The new paradigm calls for doing heavy lift with a large single-stage-to-orbit rocket.
A hydrogen-fueled heavy-lifter is big, ranging in diameter from 18 to 27 meters. Building it is straightforward. All technology needed is available. It is strictly an engineering and manufacturing task to bring it to fruition. Its sheer size should faze no one. Hundreds of tanks for containing methane on liquid natural gas ships, 36 meters in diameter, have been built and are being built.
Its size, however, removes any thought of building it in a factory and shipping it to a launch site, as is the current practice. The new paradigm calls for locating the factory at the launch site, and shipping only materials, components and subsystems to the factory.
This is not a frightening concept. At some levels it has already been done. For example, during the 1980s, the launch crew at Vandenberg Air Force Base in California accomplished all design modifications on the Atlas E and F ICBMs to ready them for flight, and then launched them. Manufacture of parts elsewhere would alleviate any geopolitical concerns about concentrating a high-dollar effort in one area of the country.
Modest-size payloads will continue to be launched far into the future. The Obama administration is taking the correct position in deciding to allow what is now a mature industry to compete for the spacecraft launch business, open to established companies and newcomers alike. Within this mandate should appear a modest-size returnable passenger vehicle. A return to X-33, on which over a billion dollars has been spent, with more practical engineering, is one idea. Powered by a row of advanced RL10 engines, this could be a long-term, useful system. Here is where NASA’s proposed million-pound-thrust, kerosene-fueled engine, if throttleable, could be applied — a recoverable stub booster for X-33.
The compelling challenges ahead in space exploration and exploitation are what NASA should be about. Obama’s rocket will usher in a new era in space exploration. It will launch payloads at one-twentieth of the cost per pound as the space shuttle. With a firm mission, orbiting turnkey space stations like Skylab, America will have launch capability for undertaking other missions, such as manned journeys to the Moon, robust robotic exploration of Mars, manned journeys to Mars, aggressive solar system exploration, and advanced work on solar power stations for beaming electrical power to Earth.
Edward Hujsak is a career rocket engineer and the author of two books on rockets, “The Future of U.S. Rocketry” and “All About Rocket Engines.”