Ares 1 launch abort: technical analysis and policy implications
by Kirk Woellert
|If the intent of a leak is in the spirit of the public good, then the information needs to be accurate and consideration given to how it will be interpreted.|
The purpose of this discussion is not to provide a rebuttal to the report conclusions. Such analysis requires considerable technical resources and is far beyond the scope of this forum. The intent is to address two points: first, the fact an apparent preliminary analysis was leaked; and second, by poorly communicating assumptions and methods of analysis behind the conclusions, the report does not lend to clarifying the design trade issues and complicates space policy formulation.
Leaks are common occurrences in public policy. In many cases they have served the public good, and in some cases they have not. However, and speaking generically, once an individual or organization decides to circumvent the normal release authority for public consumption they take on a special responsibility. Leaks in our modern society have a way of taking on a life of their own. If the intent of a leak is in the spirit of the public good, then the information needs to be accurate and consideration given to how it will be interpreted. This leads to the second point: clearly stating the basis for conclusions.
The report begins by citing the similarities between a Titan 4 solid rocket booster and the solid rocket first stage of the Ares 1 planned for the human-rated transport of the Constellation program. The Titan 4 and Ares 1 SRB have similar mechanical and propulsion characteristics. Based on these similarities the report assumes an Ares 1 launch abort will have a similar debris cloud following intentional self-destruct as an incident involving a Titan 4, which actually occurred in 1998. Whether a reasonable comparison or not should be left to the experts to validate.
The central focus of the report is what happens to the Orion capsule following intentional self-destruct of the Ares booster. The report describes in significant detail characteristics of the debris cloud and its temperature over time. According to the report, the structural integrity of the parachute shrouds is compromised when exposed to high temperatures of the debris cloud: the parachutes and shrouds material is rated to approximately 200°C while the debris cloud will be about 2,200°C. One motivator for this essay was the annotation of the Orion capsule overlaid on the still frames from the video of the Titan 4 incident. The report makes no mention of how the analysis places the Orion capsule in its position relative to the debris cloud. If one is asking “this is the effect on parachute shrouds if hypothetically the capsule were located here,” that’s one question.
However, if one is trying to ask the question, “Over the entire trajectory in a launch abort scenario, using the Titan 4 destruct as an exemplar case, will the Orion capsule parachute and shrouds survive the thermal effects of the debris cloud?” that seems to be a different question. To address the latter question one must properly simulate the proximity of the Orion capsule to the debris cloud. Such analysis must consider the performance characteristics of the Ares launch abort system (LAS), and the mass and aerodynamic characteristics of the Orion capsule. If one reads the report by the 45th Space Wing carefully it’s unclear if these parameters were utilized in its analysis.
Proximity of the Orion capsule to the debris cloud is not the only consideration. It would also seem important to take into account any delay in deployment of the Orion capsule parachute. The USAF report does not mention this operational parameter.
To be fair, one of the report references cited is the “The 6-DOF [six degree of freedom] Trajectory Animation illustrating the debris and Ares-1 relationships”. The implication being that some type of simulation was conducted, possibly using a credible aerospace analysis package like Satellite Tool Kit, which led to an associated animation. If such the case, it may be reasonable to assume the Ares LAS performance and Orion mass and aerodynamic characteristics were modeled.
|Regarding Ares 1, what the Augustine Commission needs and the public deserves—whether pro or con—is robust, objective, and clearly communicated analysis that clarifies the issues.|
The point is the reader does not know. Any scientific experiment must be subject to peer review and be repeatable. The same should apply for technical analysis. All assumptions and methodology should be clearly stated. The goal being that anyone with similar domain expertise can start with the same data and assumptions and repeat the analysis. Along the way assumptions, methodology and conclusions are challenged and are either validated or flaws are revealed.
This discussion in no way impugns on the professional abilities or character of the report author or of the 45th Space Wing. The analysis conducted is obviously within the stated mission of the 45th Space Wing. They are doing their job. NASA and the space community should always welcome an extra set of eye&. Indeed, the Orlando Sentinel article quotes Jeff Hanley, who manages NASA’s Constellation program, as saying that NASA would consider the report. As stated on the NASA Constellation program blog, NASA and the USAF routinely conduct technical exchange meetings to certify launch systems at the Eastern Range.
A wide spectrum of people, of varying levels of knowledge and interest, now has access to the conclusions stated in the report. As an example, what would a congressional staffer make of the 45th Space Wing report? Congressional staffers typically don’t have the luxury to meticulously review reports and other data. They are bottom line people who are inundated with information daily and are paid to focus on developing strategy in response to that information. Even more troubling is the effect poorly communicated technical analysis may have on the general public. The effect is more pronounced in that NASA and the Augustine committee are actively soliciting public input on the future of human spaceflight. The dramatic tagline invoked by the Orlando Sentinel may be thought as one of the ill effects.
This is a critical period of introspection for US human spaceflight and the Constellation program in particular. The Augustine committee has the tough mandate to provide reasonable options to the President in a short period of time. Regarding Ares 1, what the Augustine Commission needs and the public deserves—whether pro or con—is robust, objective, and clearly communicated analysis that clarifies the issues.