The race is on to make travel through the solar system routine.
Imagine being able to fly from planet to planet at a cost and safety level comparable to today’s flights from continent to continent. Work currently being conducted by the National Aeronautics and Space Administration could make this a reality for future generations.
Scientists at the Marshall Space Flight Center (MSFC), Huntsville, Alabama, believe that space travel is not only possible—it is inevitable. The agency’s goal is to make it cost effective and safe enough to be attractive to private industry, where it could be pursued and would flourish. The ultimate benefit will be new economic opportunities in the fields of tourism, manufacturing and medicine as well as in yet undiscovered areas.
National Aeronautics and Space Administration (NASA) officials offer the railroads and airlines as examples of the impact that new modes of transportation can have on financial growth. Entire industries grew out of the capability to move people and products easily, safely and cost-effectively from one location to another. It is important for the United States to continue pursuing space travel because, experts believe, interest from other nations in this arena is high.
Space shuttles are considered first-generation partially reusable launch vehicles. The Advanced Space Transportation Program (ASTP) is conducting research into second-, third- and fourth-generation reusable launch vehicles (RLVs).
The second-generation effort evolved out of the integrated space transportation plan developed to meet near- and long-term NASA requirements. The goal is to improve launch safety so that by 2010 the probability of losing a crew is no more than one in 10,000 missions. At the same time, researchers are aiming to reduce the per-pound payload cost of delivery to low earth orbit from today’s $10,000 to $1,000.
Compared to today’s systems, second-generation spacecraft will require launch crews of approximately 10 people rather than 170 and will need only one week to prepare for reflight compared to the current five months. They would fly up to 100 times a year; today’s flight schedule is approximately 10 missions annually.
Third-generation RLVs would further improve these numbers. Enhanced safety features would decrease the expectation of losing a crew to literally one in a million, or about the same as today’s airliners. The cost per pound of payload would be reduced to about $100. Only two ground crew members would be required to accomplish a launch, and reflight preparation would take place in one day. More than 2,000 flights would occur each year.
NASA officials predict that by 2040, no distinction will exist between commercial airliner and commercial launch vehicles in terms of operation. Fourth-generation spacecraft will be so safe and reliable that a crew escape system will not be necessary. Turnaround time between flights will be slightly longer than that of today’s commercial airplanes. Onboard crew members will conduct the launch independent of ground crew assistance, and more than 10,000 flights will occur annually.
According to Daniel L. Dumbacher, program manager for the second-generation RLV project, MSFC, his group’s effort aims at accomplishing all of the systems engineering and analysis necessary to make space travel attractive to the commercial sector, which would eventually assume this new transportation mode. “We have to convince the investors on Wall Street that the risk is low and that the business case makes more sense for them. So, we really need to find what the technical requirements are and also meet the business needs,” Dumbacher says.
Current work focuses on developing and demonstrating technologies critical to making a development decision by 2005.
“It’s going to be a challenge [to meet the deadline], but we are doing everything we can. The 2005 goal was picked through a very high-level process. The challenge is from a resource standpoint—money—and technical challenges in terms of taking the state of the art of today’s technology to where we need it to be to meet the cost and safety goals. From an information technology standpoint, we’re going to be able to use what comes out of the 18-month cycle from Silicon Valley. But putting it together in an integrated fashion is going to be the key challenge,” Dumbacher offers.
To address these problems, the team is relying on commercial off-the-shelf products to a significant level. The integrated synthesis environment helps coordinate the design process. “We have to look at the amount of time it takes to take an idea from the engineer’s head to the test model on a test stand. We’re using a lot of the technology that already exists to accomplish this and want to bring the launch industry up to speed in the information technology industry so we can take advantage of it,” Dumbacher explains.
“One of the things that doesn’t get talked about a whole lot are the foundation efforts that need to be addressed for all phases of meeting NASA’s needs such as information technology and analytical tool development. Work in these areas may be applied to second-generation [spacecraft] but may also be applied to third generation,” he adds.
Information technology also will play a key role in establishing integrated vehicle health management. By making the spacecraft smarter, flight crews would be able to react to small mechanical problems before they become more serious. The MSFC is in the process of defining the details of this project.
Although the nature of this endeavor involves space flight, the second-generation program will work with companies other than those in the aerospace community. “We are going out to the traditional aerospace companies and soliciting ideas, and [we’re] also going out to companies that have new manufacturing technology that may apply to composites, for example. We are consciously trying not to block any good ideas,” he offers. In addition to U.S. researchers, the MSFC also is tapping into the expertise that is available overseas, he offers.
On the technical side of the proposed generations of spacecraft is the basic need for a viable, affordable, safe propulsion system, and there is no shortage of ideas. At this point, researchers agree that second-generation RLVs will more than likely rely, either partially or completely, on liquid chemical rocket engines to achieve orbit.
One approach currently under development is the Fastrac rocket engine, which uses a cast Inconel 718 superalloy housing for the liquid oxygen turbopump. The pump housing will be redesigned to take advantage of the added strength and lower weight of aluminum metal matrix composite material. In addition, the ASTP is looking at modifications to the thrust chamber of the Fastrac that would regeneratively cool it, decreasing the cost and weight as well as extending the life of the engine. The MFSC also is working with several companies and universities to optimize turbine performance and develop unshrouded impeller technologies, which will increase the payload space and decrease the cost of future RLVs.
In addition to improvements to propulsion systems, space vehicles will require fuselage design and material modifications to survive numerous flights and safely transport passengers. The nature of space travel demands that craft withstand high and sustained heat. MSFC is working with organizations on advanced composite structures made from a combination of materials that may include a strong fiber, such as carbon fibers, and a matrix material, such as epoxy.
While second-generation research focuses on improving safety and reducing cost for today’s space transportation markets, third- and fourth-generation efforts aim even higher. According to Steve Cook, deputy manager, ASTP, the financial potential of space is not only untapped, all of it has yet to be discovered. From a technical standpoint, systems under consideration build on the anticipated achievements of second-generation spacecraft. However, the experimental nature of technology that is predicted to be available 40 years from now results in proposals that may be more far out than a neighboring solar system.
Despite the ultramodern nature of these spacecraft, some of today’s technologies are facilitating their development. “To a limited extent, we try to leverage the information technology software, but if you look at advanced propulsion, it’s pretty unique to what we’re trying to do. However, as much as the technologies, we are trying to use today’s processes. For example, we went to Chrysler in Huntsville, and they gave us an off-the-line controller to test a rocket engine, and it worked,” Cook says.
At the third-generation level, the ASTP is looking for basic airframe, propellant tanks and avionics approaches that meet an unprecedented level of robust simplicity. This principle applies to the manufacturing and maintenance of the vehicle as well.
By 2025, the timeframe set for third-generation RLVs, NASA officials predict that rocket engines will still propel the spacecraft, but by then technologies will have been developed that allow fundamental changes in the engine’s design. The most significant development will be reduction in the need for onboard propellant. In addition, rather than using onboard propellant for liftoff, RLVs will be launched horizontally along a track using magnetic levitation to eliminate friction and linear electric motors to accelerate the RLV to 1,000 kilometers per hour.
These improvements bring with them a multitude of benefits. Onboard engines will be able to start in ramjet mode, which eliminates the need for turbofan compressors that add complexity to systems that must be maintained. In addition, horizontal takeoff simplifies ground operations. When combined, these advantages could significantly reduce the cost of access to space.
Third-generation vehicles also will have a different look. The airframe will benefit from technology advances anticipated by 2025. Currently, a team of researchers from The Boeing Company and NASA’s Glenn and Ames Research Centers are investigating advanced high-temperature structural seals. The group is examining where seals are needed, selecting candidate materials, and designing promising candidates.
Addressing the effect of intense heat on the aircraft’s wings is another issue. Under a contract with Northrop Grumman and supported by the NASA Langley Research Center, an ASTP team is developing a high-temperature integrated wing structural concept. A large wing panel has been designed and is being fabricated, tested and analyzed to verify its performance characteristics.
If concepts for third-generation spacecraft do not already resemble science fiction enough, the design ideas for fourth-generation vehicles certainly fit the bill. “Fourth generation is like the movie ‘2001: A Space Odyssey,’ where the ship has Pan Am on the side,” Cook offers. The goal for these vehicles is to hit airline safety and cost levels, and they would be propelled using laser light or a microwave beam, he adds.
Although the ASTP’s ultimate goal is to move space travel from the government sector to the commercial sector, some companies are not waiting for NASA to achieve this objective before developing commercial spacecraft for passengers and cargo of their own. Some U.S. companies that have entered the race are Vela Technology Development Incorporation, Kelly Space and Technology, Pioneer Rocketplane, Rotary Rocket Company and SpaceClipper International. And the travel industry is not waiting either.
Space Adventures, Arlington, Virginia, a travel agency that is already booking suborbital flights predicted to take place in the 2003 to 2004 timeframe, has 100 reservations for the initial trips that would take place on spacecraft being developed by industry.
According to Bill Bell, vice president of sales, Space Adventures, the tourism market for space is large and continues to grow. “When you think about it, the people like me who grew up in the 1960s with promises of being able to travel in space when we grew up still want to be able to do just that. Our excursions allow people to fulfill their dreams of space travel,” he offers.
The suborbital flight, which is currently priced at $98,000, involves a flight of about an hour and a half, of which about 5 to 10 minutes is spent in space. However, currently available flight adventures that give passengers an unusual aerospace thrill can last a bit longer. For example, the company offers journey to the edge of space and Russian MiG-21, MiG-23, MiG-29, L-39 and Su-30 fighter aircraft excursions.
Bell agrees with Dumbacher and Cook that space tourism is certainly a market that is simply waiting for safe, economical transportation to take off. The capability to launch several flights in short periods of time multiplies the scale of the economics. If three vehicles holding 10 passengers each could fly 750 times a year, the revenue begins to hit the $5 billion market that economists currently estimate, Bell contends.
It is this economic benefit that is driving the U.S. government to pursue future generations of spacecraft. According to Dumbacher, opening up the next economic horizon—outer space—is one of the primary forces behind today’s research. “The country needs it from the standpoint that we have to constantly be pushing ourselves to open up economic activity. If we can continue to that $1,000 per pound goal, and the third generation can get to the $100 per pound goal, then we open up the opportunities,” he says.
Cook expounds on the same line of thinking. “If you look at any great endeavor that mankind has undertaken, it has involved the unknown. Doing that requires transportation. If we’re going to develop space into a place where we can live and do business—and make money—we’ve got to have the transportation, and that takes money. It’s not just ‘Let’s see what’s out there.’ We really don’t know what all the potential benefits will be. But unless we have reliable transportation to get there, we won’t be able to fulfill the promises of space.
“Also, if we want to keep the advantage in technologies, we’ve got to be at the forefront of space travel. Fundamentally, if we don’t do these things, someone else will. There’s a lot of interest in this area from the Europeans and the Japanese, and it becomes an economic security issue,” Cook concludes.