Scotty Doesn't Know
According to sources, legendary astronaut John Young claims that Ares I won't work. He says that NASA knows this, but will not announce this conclusion until May 23.
As much as I think the "Scotty Rocket" is a foolish idea, I don't think it's totally unworkable. The problem is that there's a distinct mismatch between the Orion spacecraft's mass and the Ares I's capabilities.
Orion is a train-wreck in slow motion, because NASA is trying to reconcile two very different sets of requirements. NASA wants a six-man ISS capsule and a four-man lunar capsule. Seeing as how COTS is supposed to dock with ISS, why should the same requirement burden Orion? The Orion command module should be no more than 33% heavier than the Apollo CM, due to the 33% increase in crew size. Significant mass savings can be achieved through lightweight alloys, composites, and miniaturized avionics that weren't available in the mid 60's. The Orion SM should be less massive than the Apollo SM, because there's no requirement for a lunar-orbit insertion burn, and the fuel cells of Apollo were replaced with solar arrays.
Alternately, if NASA stubbornly sticks to its "Sumo Capsule" named Orion, there are several fixes that can enhance Ares I's performance. These would include:
--Changes to the engine nozzle's expansion ratio, sacrificing thrust for specific impulse
--Changes to the solid propellant formulation in the first stage to increase specific impulse
--Filament-wound casings for some SRB segments, and deletion of first-stage recovery system
None of these changes are free of negative consequences.
--Reducing the SRB's thrust negates one of "Scotty Rocket"'s advantages, which is the depressed trajectory that allows for aborts during all flight regimes. Then again, I find NASA's original logic to be specious; the Saturn IB only had a thrust-weight ratio of ~ 1.26
--Changes to the propellant formulation will snowball into changes in the SRB casting process and machinery, and result in an all-new fuel grain design.
--Filament-wound SRB's that are expended will negate another advantage of the SRB, which is the confidence that is gained from reusing flight-proven hardware.
The biggest problem with "Scotty Rocket" is that the first stage is inherently inflexible. Solid fuel rockets can't easily be widened or lengthened like liquid-fuel stages can. The Challenger disaster and the current disaster that's called "Ares I" only vindicate Wernher von Braun's opposition to using solid rockets in manned launchers.
I am very skeptical of any unverified reports that NASA is throwing away "The Stick." NASA has blindly stuck with this monstrosity and worked through previous problems that have developed, rather than changing gears. If NASA truly is giving up on "Scotty Rocket," they will likely adopt something like "Ares IV" or its SRB-less cousin, "Ares III," to replace it. That way, NASA will be able to get money for its lunar/Mars rocket instead of putting its development off until future presidential administrations. However, Ares IV is definitely overkill for the crew launch mission. Nevertheless, NASA's reaction to more practical ideas like Atlas V and Direct Launcher has been cool at best (at times, it's been vicious and mean-spirited.)
In short, it's premature to declare the death of Ares I and celebrate. Just because it's a dumb idea doesn't mean that it will never work. It just means that it will require an inordinate amount of work and money to fix the problem; it will also lead to a system that is inferior over the life of NASA's lunar program. At this point in the program, it appears that the Orion spacecraft is in just as much trouble due to conflicting design requirements and excessive weight. At this stage in the game, it's not too late to change Orion. For the SRB-based Ares I, fixes will be much harder to make. The only way NASA can survive the crisis is through clarity of its mission and responsibility in the way it spends taxpayer dollars.
As much as I think the "Scotty Rocket" is a foolish idea, I don't think it's totally unworkable. The problem is that there's a distinct mismatch between the Orion spacecraft's mass and the Ares I's capabilities.
Orion is a train-wreck in slow motion, because NASA is trying to reconcile two very different sets of requirements. NASA wants a six-man ISS capsule and a four-man lunar capsule. Seeing as how COTS is supposed to dock with ISS, why should the same requirement burden Orion? The Orion command module should be no more than 33% heavier than the Apollo CM, due to the 33% increase in crew size. Significant mass savings can be achieved through lightweight alloys, composites, and miniaturized avionics that weren't available in the mid 60's. The Orion SM should be less massive than the Apollo SM, because there's no requirement for a lunar-orbit insertion burn, and the fuel cells of Apollo were replaced with solar arrays.
Alternately, if NASA stubbornly sticks to its "Sumo Capsule" named Orion, there are several fixes that can enhance Ares I's performance. These would include:
--Changes to the engine nozzle's expansion ratio, sacrificing thrust for specific impulse
--Changes to the solid propellant formulation in the first stage to increase specific impulse
--Filament-wound casings for some SRB segments, and deletion of first-stage recovery system
None of these changes are free of negative consequences.
--Reducing the SRB's thrust negates one of "Scotty Rocket"'s advantages, which is the depressed trajectory that allows for aborts during all flight regimes. Then again, I find NASA's original logic to be specious; the Saturn IB only had a thrust-weight ratio of ~ 1.26
--Changes to the propellant formulation will snowball into changes in the SRB casting process and machinery, and result in an all-new fuel grain design.
--Filament-wound SRB's that are expended will negate another advantage of the SRB, which is the confidence that is gained from reusing flight-proven hardware.
The biggest problem with "Scotty Rocket" is that the first stage is inherently inflexible. Solid fuel rockets can't easily be widened or lengthened like liquid-fuel stages can. The Challenger disaster and the current disaster that's called "Ares I" only vindicate Wernher von Braun's opposition to using solid rockets in manned launchers.
I am very skeptical of any unverified reports that NASA is throwing away "The Stick." NASA has blindly stuck with this monstrosity and worked through previous problems that have developed, rather than changing gears. If NASA truly is giving up on "Scotty Rocket," they will likely adopt something like "Ares IV" or its SRB-less cousin, "Ares III," to replace it. That way, NASA will be able to get money for its lunar/Mars rocket instead of putting its development off until future presidential administrations. However, Ares IV is definitely overkill for the crew launch mission. Nevertheless, NASA's reaction to more practical ideas like Atlas V and Direct Launcher has been cool at best (at times, it's been vicious and mean-spirited.)
In short, it's premature to declare the death of Ares I and celebrate. Just because it's a dumb idea doesn't mean that it will never work. It just means that it will require an inordinate amount of work and money to fix the problem; it will also lead to a system that is inferior over the life of NASA's lunar program. At this point in the program, it appears that the Orion spacecraft is in just as much trouble due to conflicting design requirements and excessive weight. At this stage in the game, it's not too late to change Orion. For the SRB-based Ares I, fixes will be much harder to make. The only way NASA can survive the crisis is through clarity of its mission and responsibility in the way it spends taxpayer dollars.
posted by Mr. X at
6:15 PM
