Last week, NASA's Associate Administrator for Exploration Systems Mission Directorate (ESMD), Scott Horowitz, sat down with reporters to discuss the Ares 1 and Orion programs. The impetus for this briefing, according to Horowitz, were recent stories - of varying accuracy - regarding weight and performance issues.
While internal sources have been talking for months about issues they saw with regard to the ability of Ares I to launch Orion, and Orion's ongoing weight issues, this issue came to a head on 11 November 2006 when I published a short item on NASA Watch.
Two days later, Constellation program manager Jeff Hanley fired off a hastily written memo. Hanley noted "many who carp from the sidelines do not seem to understand the systems engineering process. They instead want to sensationalize any issue to whatever end or preferred outcome they wish. So be it, that is the world we live in." He then went on to admit that weight and performance issues had indeed arisen stating "Both the Ares I performance and the Orion control mass are 'watch items' on our list of top program risks. This is NORMAL for any such development effort ... mass delivered to space has been and will always be a source of risk for any spaceflight project or program." Hanley closed his memo by sniping at critics: "We will continue to get these faux expressions of concern from those who wish to see us fail."
NASA followed Hanley's memo with a formal press statement on 16 November 2006 which specifically addressed the issues raised about Ares I performance: "An example of the activity was a review and analysis that confirmed the planned Ares I launch system has sufficient thrust to put the Orion spacecraft in orbit. In fact, the Ares I thrust provides a 15 percent margin of performance in addition to the energy needed to put the fully crewed and supplied Orion into orbit for a lunar mission. Engineers established Orion's take off weight for lunar missions at over 61,000 pounds."
On 4 December 2006 I posted an article "NASA To Evaluate Non-recoverable First Stage for Ares I Launch Vehicle" which said that "some of the people working on the design of NASA's new Ares I launch vehicle want to delete the requirement to recover and reuse the rocket's first stage. The reason: the weight of hardware required to make recovery possible - and practical." A day or so after this article went online, I asked when I asked ESMD Associate Administrator Scott Horowitz about this issue at the AIAA Second Space Exploration conference in Houston. He did not blink an eye in responding that the Ares I first stage "will be recoverable".
On 4 January 2007 NASA announced that the Ares I requirements review had been completed, stating: "The system requirements review confirmed that the Ares I system requirements were complete, validated and responsive to mission requirements. It also confirmed that the Ares I architecture and design concept can fulfill the mission objectives and that the Ares project is ready to begin engineering design activities. The Ares preliminary design review is scheduled for mid-2008."
On 4 January 2007 NASA also issued a presolicitation notice and a draft RFP for the Ares 1 upper stage. NASA plans to release a final RFP on or about 23 February 2007.
On 8 January NASA announced that was extending ATK's Ares I development contract to continue design and development of the first stage for the Ares I crew launch vehicle. This additional $48 million in funding was being added to a first stage task under an existing shuttle contract.
Stories have continued to appear in print and online regarding the same issues. In addition, a variety of unofficial alternate launch vehicle concepts have floated around - all with varying degrees of authenticity and technical validity. As one would expect, Horowitz was somewhat dismissive of these things and stuck firmly to the official launch vehicle development approach NASA had been following for the past several years.
Overweight or Underpowered?
The main issue that Horowitz has been trying to combat, is the widespread impression that the Ares I cannot launch the Orion spacecraft - especially on lunar missions. The flip side of the coin is that the Orion's weight has been growing as its design progressed, thus making it harder for Ares 1 to launch. It would seem, based on Horowitz's presentation, that the issue is mostly driven by Orion weight gains set against a somewhat constrained performace capability of the Ares 1 booster.
Horowitz produced several charts to the reporters present in order to illustrate the status of Ares 1 and Orion development. All spacecraft and launch vehicles are faced with a tendency to gain weight as requirements are translated into hardware designs. that is a fact of life. At any given time in this process, a snapshot might seem to show that one or more weights are outside the limits that have been set.
A simple glance at the charts showed that the projected weight of the Ares 1/Orion launch configuration had grown significantly between September and December 2006. This was due to things being added as the design process progressed. According to Horowitz "52,231 pounds is line that Skip Hadfield has to meet". Getting the overall weight to stay below that line includes all of the performance reserve or "margin" that Horowitz wants the system to have. Horowitz said that his preferred outcome would be that the Ares 1 would have 13,000 lbs of performance reserve.
Horowitz said "the Ares 1 has more than sufficient performance. The top line is what Ares 1 can deliver to orbit 58,333 pounds for a lunar mission. We have 8,102 pounds of performance reserves. The effective weight the Ares 1 is lifting has to be under 50,231 pounds. The current design is under that."
Margins, Reserves, and Bookkeeping
As is the case with any large design and development program, there is a tendency to over estimate the margin that other systems may be holding back. Other tendencies include citing margin in one system as your own, without checking to see if another part of the project is also carrying that margin as "theirs". I asked Horowitz about how such bookkeeping errors were big avoided. He described a very clear accounting process whereby the Ares 1 and Orion projects were not double counting margin and reserves.
Bookkeeping weight also needs to take into account how long that weight is part of the overall launch equation. In the case of the Launch Abort System (LAS), while it weighs in at roughly 13,400 pounds, it is discarded well before the Ares 1's payload is placed into orbit. According to Horowitz, the "effective" weight of the LAS, when all launch calculations are taken into consideration, is actually 1,675 pounds. Put another way "If I removed the LAS I'd be able to put an additional 1,675 pounds into orbit" Horowitz said.
According to Horowitz, sources of possible weight savings include the Thermal Protection System, Crew weight, cockpit hardware, avionics and other systems. In addition to design choices, there are other ways to offset weight - increasing the performance of the Ares 1 propulsion systems.
More power under the hood
One possible change has to do with the composition - and pouring of the solid rocket booster fuel. The current mixing formula is an "old formulation", according to Horowitz, one that has "nice handling characteristics." The rate at which the fuel burns is the result of the chemical formulation that is used in its mixing. This is something Horowitz said is being looked at for possible "tweaking" so as to gain some additional performance. Another possible change under consideration would be the geometry of the hollow space in the last (fifth) or uppermost segment of the first stage of the Ares 1. The change would have to do with the number of "fins" or indentations that are cast into the fuel. The current number of fins (8) might be increased to 12. This would allow increased surface area, therefore a faster burn, and more thrust at the point in the launch profile where it would be of greatest use.
Another possible performance boost might come from use of the Launch Abort System (LAS). The LAS is designed to pull the command module off of the rest of the launch vehicle - in a manner similar to that employed on Apollo - in case of an emergency situation. In the option under study, the LAS would be fired - and yet remain attached to the Command Module - (and the remainder of the launch vehicle) to give a little extra boost during the point in the mission prior to where it would be readied for disposal (around Mach 5). Using smaller rocket engines for additional propulsion is not a new idea inasmuch as the Shuttle regularly uses its OMS engines to increase overall launch performance. However, the OMS engines are not dedicated aboard and crew escape system as are those in the LAS.
According to Horowitz the studies showed that you could realize an increased delivery of around 1,000 pounds of payload into orbit. However, the mechanical and structural connections to the command module that would be required to allow this option to be implemented would eat into that payload boost - by several hundred pounds. Even if this option were to be considered worthy of the engineering changes, Horowitz seemed troubled by the prospect of using the LAS in a routine launch ascent. "If you fire the [LAS] engine nominally every flight, you have just added another stage to ascent and therefore decrease the reliability." Horowitz also expressed concern about using a crew safety system for something other than crew safety - that just detracts from the ability of that system to do its prime task. Although Horowitz would not discount this LAS option out of hand, it was obvious that he was not very enthusiastic about it - but he said that it was still under study to see "if there is any gold to be mined there."
A better Aim on the way home
Another item under study by NASA - and one responsible for some of the margin that is needed - has to do with reentry. Horowitz said that "skip entry" was being studied as a way to better control landing site aim - and to make last minute changes if one site becomes unavailable for some reason. Horowitz said that this was an option available - but never used - during Apollo. In essence, the Command module would enter the Earth's atmosphere, slow down, and then skip out again. After a period of time it would reenter once again and descent to its landing site. The issue under study is whether the Thermal Protection System's ablation system's chemistry will allow it to go from prolonged cold exposure ("cold soak"), heat up to high temperatures, cold soak again, and then be reheated.
During the flight testing phase of Orion's development , flights, some of then unmanned, will be flown to test various systems. One thing Horowitz said would likely be done is to fly a mission whereby the Command Module's head shield is tested at the speeds expected during a return form the moon. One way to do this might be to launch an unmanned Command Module, with out an escape system (to save weight) and put in as much fuel as possible. Something like this was done on Apollo 4 and was planned for Apollo 6.
Another option that might be available (based on a study done at MSFC) would be to use some Ares 1 components and some Ares V components. When I asked Horowitz about the rumored "Ares IV" he replied that some ideas had been studied (although he refrained from using the term Ares IV). He suggested that NASA might want to test some Ares V systems and Orion systems by flying the Ares 1 upper stage atop a Ares V first stage. This would probably result in putting the entire Ares 1 upper stage and into orbit. A series of engine firings would then put the Orion on a trajectory that would allow it to experience lunar reentry speeds.
New Rockets in Their Back Pockets?
When I asked Horowitz if this Ares IV as part of an alternate architecture to implement the VSE he more or less dismissed the notion. Specifically, the "Ares IV" was not being considered as a replacement for the human launch capability of the Ares 1. Mike Griffin said the same thing a week or so earlier at a Space Transportation Association breakfast when I asked him the same question.
Horowitz also downplayed the notion put forth by some that you might use two "Ares IV" vehicles - one for crew, the other for the lunar lander, as an alternate way to get humans to the Moon. Among other things he said that such an approach would require dramatic changes to the LSAM (lander).
Horowitz certainly put forth a positve picture of Ares 1 and Orion developement. Yes, there are weight growth issues. Yes, NASA is tracking them. No, NASA does not feel that its proposed launch systems will be incapable of doing their job when called upon to do so.
Horowitz said that he now hopes to have regular press updates - perhaps on a monthly basis. This is a smart thing to do - if for no other reason than to try and shoot down rumors at an early stage and/or admit to problems before arm waving outpaces facts.