Staying the course in a sea of change
by Jeff Foust
|The transition team has been tight-lipped about exactly what policy changes they are considering, leaving outsiders to engage in a form of Kremlinology by divining intent based on the questions the team has asked (or not asked) NASA.|
In an interview with The Space Review last week, though, Ares projects manager Steve Cook said that NASA was making good progress with the two best-known technical issues with the Ares 1, thrust oscillation and liftoff drift. On the thrust oscillation issue, Cook said that engineers had been working on two approaches: “detuning” the launch vehicle stack from the frequency of the motor through the use of an isolator, and reducing the amplitude of the oscillation.
In August, Cook said, the project decided to pursue two passive methods of isolation. A baseline approach was a “spring ring” design: mounting approximately 200 C-rings around the inner circle of a joint between the forward frustum and interstage at the top of the first stage. “Those allow you to maintain the lateral stiffness of the vehicle so you can control it, but detunes the vehicle significantly,” he said. This approach also makes it straightforward to change the tuning based on the results of ground tests and unmanned flight tests, he added.
An alternative approach under consideration was the “shock ring”, which Cook described as bands of metallic structure with bows built into them; the project also looked at ways to lay up the composite materials used in the vehicle differently to help detune it. At the project’s recent “PDR+90” review, held 90 days after the vehicle’s preliminary design review (PDR), Cook said the baseline “spring ring” approach won out, although using the vehicle’s structure to detune itself emerged as a more elegant long-term option. “We really like the idea of using the inherent structure that you’ve got without having to add anything,” he said, “but it didn’t give us much flexibility if we miss our tuning mark.”
Earlier this year an active system of shock absorbers in the base of the vehicle got some attention as one way to reduce the amplitude of the oscillations. However, Cook said that option was put on the backburner at the PDR+90 review. “There’s a lot more things that have to go on there: you have to develop the control system, the power system, things of that nature,” he explained. Instead, NASA will pursue a passive version of that system, but keep the active version as a backup.
The liftoff drift issue, Cook said, stemmed in part from “a very robust requirement” of being able to launch in winds of up to 34 knots (63 km/h), compared to 19 knots (35 km/h) for the shuttle. “What we found was that, 0.3 percent of the time, we would get a wind from the south of that magnitude, and if that were to happen, and we were to do nothing, we could impact the tower.”
However, there are a variety of options the project is pursuing, from using the rocket’s active thrust vectoring control system to fly away from the tower at liftoff to simply lowering the wind limits to something closer to what the shuttle operates under. “We know we won’t hit the tower,” he said. “We’re focused on how do we minimize damage to the tower [from the rocket’s plume] so we can make this the lowest recurring cost approach as we move on.”
|“A lot of the experts we bring in from time to time that have been through the Apollo and Shuttle eras said that we were farther along at PDR [for Ares 1] than they were at that stage in the game,” Cook said.|
Cook and others also defended the September Ares 1 PDR despite reports that the review uncovered a number of problems with the vehicle’s development. “I attended the review myself, and despite what was said in the blogosphere and the sensational media, it was very professionally done,” said Doug Cooke, NASA associate administrator for ESMD, during a speech at a Space Transportation Association luncheon on Capitol Hill on December 12. The number of “yellow and orange” evaluations that came out of the PDR, he said, was because the review was focused on those issues. “So we asked a lot of hard questions, and I have to say that the team was especially well-prepared.”
“That was a very successful review from our perspective,” Steve Cook said in his interview. “I think there’s a lot of people who think when you finish a preliminary design review, you tie a bow around it, everything is summed up all nice and pretty and you’re ready to move on to the next step. On a large, complex, integrated system like that, that’s not how it works.”
Cook said the project got an endorsement from a panel of outside experts, including people who worked on the shuttle and Apollo programs. “A lot of the experts we bring in from time to time that have been through the Apollo and Shuttle eras said that we were farther along at PDR than they were at that stage in the game.”
Another key issue facing Constellation has been the extended gap between the shuttle’s retirement in 2010 and Constellation’s introduction into service, now planned for late 2014. How much that gap can be shortened, and at what cost, has been the subject of intense scrutiny, including at NASA.
Jeff Hanley, Constellation program manager, said in an interview with The Space Review last week that the agency had recently completed a study led by Ralph Roe, director of the NASA Engineering and Safety Center (NESC), and including the deputies for all the line organizations within Constellation, to study various options for accelerating the Ares 1/Orion initial operating capability (IOC).
The first part of the study was to look at the shortcomings in the current plan that could prevent the planned IOC of September 2014. “That will require more money to go to that more robust plan to achieve the September 2014 date, on the order of a couple of billion dollars,” Hanley said. Moving the IOC back to the previous IOC date of September 2013, he added, would not cost much additional money: about $2.5 billion over the next two years. He added, though, that the September 2013 date is “very success oriented, but not un-executable.”
A third option the study examined was to further accelerate IOC to March 2013. “Based on where we’re at today, and what it takes to develop these very complex systems—the rocket, the spacecraft, and all the ground and mission systems—that accelerating that much is just technically not possible,” Hanley said.
That additional $2 billion or more would have to come in the next two years, fiscal years 2009 and 2010—and fiscal 2009 started on October 1, although Congress has not completed work on a final appropriations bill for NASA for 2009. “These next two years are the critical years,” Hanley said. “’09 and ’10 are what really govern the pace at which the program can execute right now.”
|Hanley said it’s “just technically not possible” to accelerate the introduction of Ares 1 and Orion to March 2013, 18 months earlier than the current plan.|
He said the funding profile for a “normal, healthy” program was markedly different than the constrained budgets Constellation has been operating under. “You want to be ramping up to an apex that will occur at the critical design review,” to buy down the risks before going into manufacturing and operations. “For us, critical design review is in the early 2011 timeframe.”
Both Cooke, in his STA speech, and Cook and Hanley, in their interview, played up the active year coming up for Constellation, headlined by the Ares 1-X launch planned for mid-2009. Other highlights range from a test of the Orion’s launch abort system in early 2009 and the spacecraft’s PDR in August to the launch of NASA’s Lunar Reconnaissance Orbiter in the spring. All three were confident about the program’s future and the direction the agency had chosen for the exploration program, despite the criticism from some quarters.
“I think we have a superior architecture today as to what came out of ESAS,” Hanley said, referring to the Exploration Systems Architecture Study in 2005 that resulted in the general approach being pursued. “I think we’ve made very smart changes. At the top level they might seem to be under-the-hood changes because cosmetically we really haven’t changed the fundamentals of the architecture. We made strategic improvements to be able to leverage the investments we’re making in these early years.”
Referring to Ares 1 specifically, Cook noted that launch vehicle studies had been underway at NASA since days after President Bush announced the Vision for Space Exploration in January 2004. “A lot of people think the ESAS study was a 90-day study,” he said, and thus raise questions about its conclusions. “Well, ESAS was fed by hundreds of studies that had been done over the previous decades… Frankly, I didn’t care, and neither did Jeff [Hanley] nor anyone else on the team, what the answer was, we wanted the lowest-cost answer, we wanted the highest reliability for the system.”
Cook brushed off the critics of Ares 1. “Launch vehicles throughout history have always been something of a lightning rod,” Cook said. “Saturn had its critics, Shuttle had its critics.”
|“Launch vehicles throughout history have always been something of a lightning rod,” Cook said. “Saturn had its critics, Shuttle had its critics.”|
Hanley added that those who propose alternative systems don’t take into account all of the requirements Constellation has to meet. “We have rigorously revisited all of the options traded once we pinned down what that mission was, traded all that in ESAS, laid it all out apples-to-apples as best we could, and then let the data lead us to the answer,” he said. “There are those out there who don’t want to believe that the data led us to this answer, but it’s in the report.”
Despite their confidence in the architecture, though, it could all be for naught if the new administration decides to go in a different direction. “I don’t think we’d be human beings if we didn’t worry about any change,” Hanley said. “We believe in the plan that we’ve laid out. If the nation chooses to alter that plan, we will do our very best to execute that in good faith.”
Cooke noted in his speech that the future direction of NASA’s exploration program will depend on the new administration and Congress. “We do not know yet what that direction is,” he said, “but we will, of course, adapt to the changes in direction, if there are any, when we receive them.”