I learned to ride a bike with training wheels. They kept me from falling over. They also slowed me down. After a month or two, I took the training wheels off and really started to ride. For decades, American companies have flown people into space under the strict government supervision, training wheels that got us started and, most of the time, kept us safe.
It's time to take the training wheels off and fly. This means NASA's top human space flight priority should be the Commercial Crew Program. This program is helping American companies develop privately owned space taxis to take people from Earth into Low Earth Orbit, especially the International Space Station (ISS). The primary alternative is the Space Launch System (SLS), a program to pay private companies to develop a much larger 100% government owned vehicle with strict government oversight -- training wheels. It should be noted that right now, American astronauts travel to the ISS on Russian vehicles.
With today's massive federal debt and deficit, choices must be made. In the case of human space flight, I believe that the Commercial Crew Program should be fully funded first because:
1. Commercial Crew is far, far cheaper than the SLS. Total cost is around $6 billion for the largest Commercial Crew proposal vs. the $35 billion estimated for the SLS. Furthermore, Commercial Crew uses fixed price contracts and the SLS will be traditional cost-plus accounting, an approach that rewards cost over runs. The lower cost is fundamental, Commercial Crew takes advantage of market forces.
2. Commercial Crew vehicles are expected to fly humans many years sooner than the SLS. Thus, less money will be paid to the Russians.
3. The SLS is too large for efficient transportation of people to the ISS. This also increases cost.
4. Commercial Crew is intended to develop multiple space taxis by multiple companies. No longer will America depend on a single launch vehicle for human access to space. In the shuttle era, each accident was followed by years of cancelled flights. Multiple vendors will reduce this risk substantially.
5. Commercial Crew is intended develop space taxis that can sell rides to others. For example, Bigelow Aerospace has put two small space stations in orbit and once a space taxi is available is prepared to fly a full sized space station to host astronauts. The Commercial Crew vehicles are perfect for space tourism, a market that is currently a Russian monopoly. Space tourism has the potential to vastly increase the number of people in space.
If Commercial Crew is fully funded and Congress wants to fund the SLS or other human launch alternative, I support that. But, only when the best alternative, Commercial Crew, is fully funded.
For fifty years American companies have built and operated human launch vehicles under strict government ownership and supervision. It's time to take off the training wheels and let private enterprise fly.
NOTE: While the SLS is a much larger vehicle than those proposed for Commercial Crew, at least one private company is prepared to build similarly large vehicles at much lower cost. Specifically, SpaceX believes the can build a vehicle with a greater payload than the SLS for approximately $2.5 billion in five years (link).