Commentary | Tales of Recent U.S. Space Exploration Insufficiency


The White House proposes, and the Congress disposes. Any new U.S. space exploration initiative falls under this process codified by the Constitution’s separation of powers. Unfortunately, very few space initiatives the Obama administration proposes meet with a favorable congressional disposition in the form of authorization and sufficient allocation of funds. Let’s review two such proposals from the perspective of sufficient preparation before submission to Congress. The first of these proposals will set historic perspective for the second.

During the Obama administration’s first year, the Review of U.S. Human Space Flight Plans Committee was chartered to advise the NASA administrator and the director of the White House Office of Science and Technology Policy regarding plans, programs and alternatives for future U.S. human spaceflight that are safe, innovative, affordable and sustainable. Under this charter, the committee, chaired by former Lockheed Martin Chief Executive Norman Augustine, issued in October 2009 a report titled “Seeking A Human Spaceflight Program Worthy Of A Great Nation.” The committee’s deliberations were highly transparent, multiple hearings across the U.S. were open to the public, and its report saw unrestricted distribution.

In contrast to the Augustine committee’s conduct, subsequent White House actions culminating in its February 2010 budget proposal to Congress were opaque even to NASA. Regarding human spaceflight, this proposal canceled the Constellation program and its lunar exploration initiatives, set a goal for human spaceflight to a near-Earth asteroid by 2025, and ceded international space station U.S. crew logistics to commercial firms. The committee’s report provided limited technical basis for the budget proposal, but NASA made no direct input to the White House vetting this proposal, particularly the 2025 milestone’s feasibility.

Any coordination with the Congress by the White House regarding its 2010 game-changing human spaceflight budget proposal was also opaque. If such coordination occurred at all, it was not sufficient to build consensus. Opposition in Congress has been bipartisan and entrenched to this day.

Since February 2010, NASA has had time to fully scope technology gaps to be surmounted before safe human spaceflight to an asteroid can be attempted. Fundamental and timely progress will be required in highly reliable propulsion and human life-support systems to achieve the 2025 milestone. Reducing these challenges to a manageable level requires that round-trip mission duration and change-in-velocity be minimized to a degree that the number of human spaceflight mission opportunities to known near-Earth asteroid destinations during the first half of the next decade is arguably not sufficient. In addition to an accessible orbit accurately predictable to circa 2025, an asteroid destination must be sufficiently close to Earth at a programmatically desirable time for a viable mission opportunity to arise. The asteroid must also possess rotational dynamics and physical properties permitting the crew to safely study it at close range and obtain samples. Thus, the number of known near-Earth asteroid destinations accessible for human spaceflight circa 2025 is arguably on the order of 10 or less.

The tale of insufficiency begun in 2010 spawned a sequel this year. Like its predecessor, this story opened with a publicly distributed technical report. Titled “Asteroid Retrieval Feasibility Study,” the report was published in April 2012 under sponsorship of the Keck Institute for Space Studies with contributors from NASA, the European Space Agency, academia and space interest groups. By April 2013, the White House and NASA leadership had morphed the Keck report into a dozen publicly available charts collectively titled “NASA’s FY2014 Asteroid Strategy.”

The NASA charts serve as rationale for a new space initiative called the Asteroid Redirect Mission (ARM) proposed to Congress for $105 million of initial funding in fiscal year 2014. The charts advocate an assessment of near-Earth asteroids in solar orbits sufficiently Earth-like that one with mass of about 500 metric tons could be captured in free space and nudged into stable orbit about the Moon by a robotic spacecraft using solar electric propulsion. To facilitate capture, the target asteroid must be  approximately 10 meters in diameter or smaller, and it must rotate in a stable manner at approximately 1 rpm or less. Astronauts could then access and study the asteroid in its new orbit during three-week missions conducted “as early as 2021.”

The ARM concept offers potential advances in solar electric propulsion technology, in techniques diverting asteroids from Earth impact, and in understanding near-Earth asteroid formation and evolution. It also provides human access to an asteroid during early cislunar test flights before additional systems required for safe transport in interplanetary space will be operational.

But ARM has not been sufficiently vetted by NASA or its academic, commercial and international partners. This has led a House subcommittee to draft legislation explicitly prohibiting NASA from further ARM development. Technical issues with which NASA is grappling to build ARM credibility are manifold:

n The current ARM concept further restricts the insufficient number of known near-Earth asteroid targets suitable for human spaceflight without redirection. An ARM opportunity occurs when the targeted asteroid would otherwise approach Earth within approximately 15 million kilometers at a geocentric speed of less than about 2 kilometers per second before 2021. Such a close Earth approach is also required to discover a small near-Earth asteroid, and its next return (offering the earliest ARM launch opportunity) could easily be a decade or more afterward.

n A small near-Earth asteroid’s observation window is typically too brief to reduce orbit uncertainties and provide sufficient prediction accuracy for ARM trajectory planning. Fleeting observation opportunities also make it difficult to schedule and accurately point radar antennas when a small asteroid is sufficiently close to Earth for echo detection. These radar observations are the only practical means to determine the asteroid’s diameter and its rotational state with sufficient precision to qualify as an ARM target.

n Free-space capture experience with slowly rotating but otherwise cooperative satellites having masses less than 10 metric tons does not bode well for ARM. This operational experience involved responsive human-controlled systems during the space shuttle program and chronicled unreliable results (Solar Max on STS-41C and Intelsat 6 on STS-49). The ARM capture technique must employ autonomous robotic systems because it will likely occur tens of light-seconds from the nearest human operator. Until actual asteroid capture, there is no means of determining its mass with sufficient precision to ensure it can be redirected into a stable lunar orbit.

With conceptual modifications to ARM, this initiative’s credibility may yet be restored in Congress. In the original Keck report, an option to extract near-Earth asteroid samples from an approximately 100-meter diameter target was suggested. Such a target would be more easily observed farther from Earth over longer time intervals. It would more likely exhibit stable and slow rotation, and it could offer multiple sample options including monolithic boulders of many sizes and rubble likely spanning a spectrum of origins. Reduced ARM sample mass could result in a sufficient number of viable targets. Such a modified ARM would not compromise any of this initiative’s technology, planetary defense or planetary science objectives.

To summarize, it appears current White House civil space exploration policymakers have been giving us sufficient inspiration when proposing new initiatives, but those proposals would fare better if technical experts were allowed to expend sufficient perspiration before submission to Congress. Only after thorough vetting by these experts do such proposals have the credibility to withstand congressional scrutiny and seriously compete for sufficient funding.


Daniel R. Adamo is an independent astrodynamics consultant with research interests in space mission design throughout our solar system. From 1990 until 2008, he supported 60 space shuttle missions from NASA Mission Control’s Flight Dynamics Officer Console. He welcomes feedback at