With Russia threatening to end its participation in the International Space Station (ISS) program and possibly even removing one of its major components from the orbiting space station after 2020, some have questioned whether the US can continue its $3 billion a year commitment to the ISS program beyond 2020.
Originally, the US had planned to decommission the ISS after 2016 in order to utilized those funds for the Constellation program which was supposed to place American astronauts back on the surface of the Moon before the end of the decade. But the Obama administration decided to end the lunar program in order to continue the ISS program. But now thanks to tensions with Russia over the Ukraine, the future of the ISS is cloudy.
Congress, however, decided that America needed to develop a heavy lift vehicle (the SLS) in order to enable American to have the lifting capability to deploy human spacecraft destined for the Moon and Mars. But the ISS could also provide America with the means to quickly and cheaply replace the ISS with a new generation of larger and cheaper private and SLS derived space stations.
NASA's future Space Launch System (SLS) won't be fully operational until it can utilize the new expendable RS-25E engines which probably won't be ready until the year 2021. However, NASA has 16 Space Shuttle Main Engines (SSME: RS-25D), previously used by the Space Shuttle stored away for use by the SLS. Since the SLS will utilize four engines per flight, the SSME could launch up to four SLS missions before the arrival of the expendable RS-25E engines. But the safety of astronauts launched on the SLS may depend on utilizing these engines on unmanned test missions.
Simulated Video of Delta IV Heavy Launch of the CM of the MPCV
In 2014, NASA will use the ULA's Delta-IV heavy to test launch the Command Module (CM) of the future Multipurpose Crew Vehicle (MPCV), placing it in low Earth orbit for reentry back on Earth. The Service Module (SM) of the MPCV, however, will still be under development by the European Space Agency and won't be available to launch with the CM until 2017
The SLS heavy lift vehicle will make its maiden launch in 2017 along with the complete version of the MPCV . This unmanned flight could be as simple as sending the MPCV to TLI (TransLunar Injection) or on more complex journeys to the Earth-Moon Lagrange points or to some other points of interest within cis-lunar space.
After 2017, NASA has no SLS missions scheduled until 2021 when the first crewed missions of the SLS/MPCV are scheduled to begin and the new RS-25E engines are scheduled to be utilized. It would also mean that astronauts would be launched on top of the SLS after just one unmanned test flight! But NASA would still have 12 SSME that could be utilized for cargo missions before 2021 that could further insure the safety of the SLS for manned spaceflight.
During the Apollo era, there were two unmanned test flights of the Saturn V heavy lift vehicle before NASA finally took a chance and launched three American astronauts into orbit around the Moon in December of 1968. The first unmanned test flight of the Saturn V in November of 1967-- was a complete success. However, there were some problems with the second and third stages of the Saturn V during the second unmanned test in April of 1968.
Of course, serious problems with the Apollo Command Module occurred during a launch rehearsal test on January 27th, 1967 which cost the lives of three American astronauts: Virgil I. "Gus" Grissom (a former Mercury astronaut), Edward H. White (the first American to walk in space), and Roger B. Chaffee-- an astronaut who never got a chance to fly into space.
So as far as safety is concerned, I believe it would be prudent for NASA to launch the SLS more than just one time-- unmanned-- before actually placing living human beings on top of the new heavy lift vehicle.
But that doesn't mean that such early SLS flights can't also be put to good use. Below is a proposal for two additional SLS flights before the first manned flight of the SLS/MPCV in 2021:
I propose that in 2019, NASA should launch the Bigelow Aerospace company's Olympus BA-2100 space station to LEO for-- private commercial utilization. While Bigelow Aerospace would pay for the development of the BA-2100, under this scenario, NASA would pay for the launch of the habitat in exchange for up to 60 days of annual exclusive use of the facility-- with the exception of Bigelow Aerospace maintenance personal aboard the space station.
This would give Bigelow Aerospace the advantage of having a huge space station in orbit for exclusive fee based Commercial Crew and foreign spacecraft visitations at least 10 months out of the year. Bigelow could still pay private launch companys to deploy its smaller microgravity facilities (BA-300) nearby. This would allow small specialized microgravity labs to function without human interference while the human engineers and scientist took shelter at the larger Olympus space station until the experiments are completed and the results can be retrieved from the smaller facilities. Human access to the Olympus space station will, of course, depend on the availability of operational Commercial Crew spacecraft which should be available to NASA well before 2019.
I also propose that in 2020, an orbital habitat derived from the SLS hydrogen fuel tank, similar to the Skylab 2 proposal, also be deployed by the SLS to LEO. Such a habitat could be equipped with a six meter in diameter internal hyper gravity centrifuge-- easily accommodated within the 8.4 meter interior diameter of the space station. This will enable NASA to see if one to two hours of hypergravity per day can significantly mitigate some of the deleterious effects of microgravity on the human body. The new NASA space station will also be supplied with enough water shielding to protect astronauts from major solar events while also reducing their long term exposure to cosmic radiation. Again, NASA will need to utilize Commercial Crew services in order to access the SLS deployed NASA space station at LEO. In the 2020's, a similar SLS derived habitat will be placed at one of the Earth-Moon Lagrange points and could someday be used to house astronauts on interplanetary journeys.
So before the Space Launch System is fully operational in the early 2020s, the old Space Shuttle Main Engines could allow the SLS to deploy two enormous space stations: one privately owned and one owned by NASA. Both stations could serve as places of refuge if one of the stations had to be abandoned in an emergency. And they could both serve as way stations for future reusable Orbital Transfer Vehicles headed towards the Earth-Moon Lagrange points or to Lunar orbit. A new generation of space stations would allow NASA to finally move beyond the ISS while focusing its efforts and finances on beyond LEO missions to the Moon and beyond.
Adding two additional unmanned SLS launches should help to enhance the launch vehicles safety and reliability before manned missions begin in 2021. And, under this scenario, four SSME would still be available in case the RS-25E engines are still not ready for manned SLS missions by 2021.
Links and References
Utilizing Space Shuttle Main Engines (SSME) for Early SLS Cargo Launches and Commercial Crew Destinations
An SLS Launched Cargo and Crew Lunar Transportation System Utilizing an ETLV Architecture