The Constellation Program is building and testing hardware and achieving program milestones in the development of the Ares 1 launch vehicle and Orion crew capsule.

At the same time, however, there is ongoing promotion of substitutes for the Ares 1 and Ares 5 launch vehicles. These arguments include unsubstantiated claims of performance, cost, schedule and work-force benefits. Authors of articles promoting concepts, such as “direct,” attempt to speak for NASA and accuse it of stifling debate, hiding information and driving to design solutions for malevolent reasons.

During almost 35 years at NASA, I have witnessed a work force and management team that is dedicated, conscientious and believes fervently in NASA’s mission. The management team at NASA works more collaboratively today than I have observed in the past.

The NASA team is making decisions and doing everything in its power to make programs as successful as possible. Inevitably, conflicting technical perspectives and requirements arise that must be resolved. Very few choices in life evoke a unanimous consensus. NASA leadership has been very open in explaining the rationale for decisions and the approach being taken.

Based on my experience working on the space shuttle and space station programs, I submit that today we are working decisions and issues more publicly than ever before, amplified by the level of communication and access to information on the Web and blogosphere.

There comes a time in a program when decisions are made and programs move forward. Mike Griffin became NASA administrator in 2005 and he immediately chartered the Exploration Systems Architecture Study to take one last look at the transportation architecture before setting the implementation in motion.

This study took into account years of past NASA studies and the full range of potential future missions, beginning with the international space station, the Moon, Mars and other destinations. Many candidate concepts were evaluated, and each compared performance, crew and mission risk, development cost and life cycle cost with the requirement to fit within the available NASA exploration budget.

Shuttle-derived, Evolved Expendable Launch Vehicle (EELV)-derived and combinations of the two were evaluated.

The decision was made to split crew and cargo, an idea which has been advocated since the investigation of the Challenger accident.

The Ares 1 crew launch vehicle and Orion Crew Exploration Vehicle concepts were chosen to launch crews into orbit. It is the simplest design to do this job; there is not excess performance by design.

Other shuttle and EELV concepts considered require multiple propulsion components – engines, tanks, boosters, etc. – for the first stage. These multiple components are not redundant to each other. The “direct” concept fits into this category. NASA has posted its analysis of the “direct” concept online at

By comparison, the Ares 1 design employs a single solid rocket booster for the first stage. It has an upper stage, as do other concepts.

The simplicity of the combined system of the Ares 1 rocket and Orion crew module provides the best probability of crew survival on ascent over all other concepts we know of by a factor of approximately two.

In simple terms: the fewer the moving parts, the lower the risk. After basic performance is achieved, crew safety is the most important discriminator in comparison of vehicle concepts.

Also, the development and recurring cost for this approach is lower than the others evaluated. Once again, in simple terms: the fewer the parts, the lower the cost for development and operations. For end-to-end lunar performance, the Ares 5 shuttle-derived vehicle is unique in having the performance capability necessary to perform the mission in the minimum number of launches and cost.

Decisions were made in 2005 to begin development on what have become the designs for the Ares 1 and Ares 5 rockets and the Orion crew capsule. Since then, all Constellation efforts and resources have been dedicated to implementing that decision and making progress with all possible haste. NASA and contractor teams are in place for Orion and Ares 1.

The time is past for considering alternate concepts. To revisit that decision three years later would be counterproductive, disruptive, costly and potentially dangerous to the survival of the Constellation Program.

The Space Station Program nearly ended in 1993, following a redesign of Space Station Freedom. After years of modifications, the redesign resulted in a different combination of most of the same components. It survived Congress that year by a single vote. Congressional members who devotedly had supported Space Station Freedom for years felt they had been betrayed by NASA’s suggestion that the design was flawed. The program’s progress, and the civil service and contractor work force, were put on hold for about a year while the redesign was conducted, the new program management structure was established, and the hardware design was baselined and negotiated into contracts.

Similarly, the cost of putting the Ares and Orion work force on hold and potentially scrapping hardware could be $3 billion or more.

There is no need to do this when real progress is being made. All technical problems are workable. Revisiting these decisions now would cause a loss in momentum and potentially waste the work and investment made during the past three years. It inevitably would extend the gap between retirement of the space shuttle and operation of the new Orion and Ares 1 system.

In summary, the path has been decided. The program is making substantial progress, managing technical issues, building and testing hardware and moving ever closer toward flight tests. The best chance of attaining the earliest possible human flight operations with the new transportation system is to continue on the present course.

We appreciate the tremendous support NASA is receiving. We trust that our stakeholders will continue to support NASA’s current direction. We hope for broader support from our relatively small community, which ultimately will benefit from this opportunity.

For our part, we will continue to work within the budget to build a safe, efficient and flexible system to advance human space exploration.

Doug Cooke is the deputy associate administrator for NASA’s Exploration Systems Directorate.