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Sounds like the alternatives of launching Orion, the "space shuttle replacement" that really isn't, on the Delta IV, Atlas V or, heaven forbid, a SpaceX Falcon 9 Heavy will have to be addressed.....
Link....
Death knell for NASA's Ares rockets?
NASA's new Ares I launcher has problems: it's too small, it has various technical snags like excessive vibration, and its cost and schedule estimates are worsening steadily. The Augustine Commission is currently investigating whether NASA is really on the right track with it. Now a new problem has surfaced, and it's bad, possibly the death knell for Ares I.
Ares I's first stage is a derivative of the shuttle's Solid Rocket Booster (SRB). This was considered acceptable because of the SRB's supposedly-excellent safety record (it's only killed one crew...), and because the agency's future Orion crew capsule, unlike the shuttle orbiter, would have an escape system to pull it clear of a malfunctioning rocket.
Unfortunately, it turns out that if an abort occurs any time in a sizable part of Ares I's SRB burn, then even if the escape system works perfectly, the capsule will crash and the crew will die.
The Orion capsule uses an escape system quite like that of the Apollo spacecraft in the 1960s and 70s: an "escape tower" containing a solid-fuel rocket that will pull it up and away from Ares I in a pinch. It will then descend under its parachutes, as in a normal landing.
Using an SRB for the first stage does have its problems. Solid-fuel rockets can't easily be shut down on command. Moreover, they have quite high thrust, so Ares I accelerates quickly, reaching high speeds while still in dense air. The combination means that Orion's escape rocket has to be unusually powerful, because it has to pull the capsule away from a still-accelerating rocket, against a fierce wind blast.
Whether solid rockets are more or less likely to fail than liquid-fuel rockets is debatable. More serious, though, is that when they do fail, it's usually violent and spectacular. So an analysis had to be done: would an escaping Orion be hit by fragments of an exploding SRB?
If the accident occurred during the time of high wind blast – at least the period between 30 and 60 seconds after launch, maybe longer – an escaping Orion wouldn't be able to pull clear of the fragment cloud. Something similar happened in 1998, when a Titan IVA rocket exploded about 40 seconds after launch. It had two somewhat smaller SRBs, but the total load of solid fuel was only a little less than an Ares I SRB, and various other aspects were broadly similar. The debris cloud generated in that accident was half a kilometre across within about 3 seconds, and about 5 km across within about 20 seconds.
But that analysis discovered a much more serious problem, one that nobody had noticed. The big problem is that much of that debris is big chunks of flaming solid fuel, still burning at over 2000 °C. For an accident anywhere in that vulnerable period, Orion will be inside the blazing debris cloud for its whole descent. And its parachutes are nylon, which melts at about 200 °C. They will overheat and disintegrate, and the capsule will crash.
Past experience, on the shuttle and the Titan rockets, suggests that large multi-segment solid rockets have a probability of failure of 0.5 to 1 per cent. Since a failure would be unsurvivable during about a third of the SRB burn time, that puts the chance of losing a crew on each Ares I launch at 0.2 to 0.3 per cent. This is a far higher risk than NASA's modern rules permit.
This problem also affects various other shuttle-derived launch concepts, like the "Direct" scheme advocated by some NASA engineers.
In principle, a still more powerful escape rocket would solve the problem. In practice, the Orion escape rocket is already very powerful, making it very heavy and producing really brutal accelerations if it's activated in milder conditions. Beefing it up still further is probably impractical.
The problem could be avoided by using a different landing system for the capsule. For example, if it landed on rocket thrust instead of parachutes (like the Lunar Lander Challenge vehicles), it wouldn't be so vulnerable to heat.
For another example, there was some study of landing the Apollo capsule with a helicopter rotor rather than parachutes. But such alternatives would require serious redesign of Orion, and significant development work of their own... and today's NASA is reluctant to seriously consider such unorthodox approaches.
Most likely, this problem will be the kiss of death for flying manned spacecraft on large solid rockets. NASA will have to grit its teeth and abandon Ares I, in favour of flying Orion on Delta IV or Atlas V rockets. These rockets, now mostly used to loft communications satellites, come in configurations that use only liquid fuels.
That was arguably a better approach all along... and now it's going to be really hard to do anything else but that. NASA's own rules say that Ares I is impossibly unsafe.
NASA's new Ares I launcher has problems: it's too small, it has various technical snags like excessive vibration, and its cost and schedule estimates are worsening steadily. The Augustine Commission is currently investigating whether NASA is really on the right track with it. Now a new problem has surfaced, and it's bad, possibly the death knell for Ares I.
Ares I's first stage is a derivative of the shuttle's Solid Rocket Booster (SRB). This was considered acceptable because of the SRB's supposedly-excellent safety record (it's only killed one crew...), and because the agency's future Orion crew capsule, unlike the shuttle orbiter, would have an escape system to pull it clear of a malfunctioning rocket.
Unfortunately, it turns out that if an abort occurs any time in a sizable part of Ares I's SRB burn, then even if the escape system works perfectly, the capsule will crash and the crew will die.
The Orion capsule uses an escape system quite like that of the Apollo spacecraft in the 1960s and 70s: an "escape tower" containing a solid-fuel rocket that will pull it up and away from Ares I in a pinch. It will then descend under its parachutes, as in a normal landing.
Using an SRB for the first stage does have its problems. Solid-fuel rockets can't easily be shut down on command. Moreover, they have quite high thrust, so Ares I accelerates quickly, reaching high speeds while still in dense air. The combination means that Orion's escape rocket has to be unusually powerful, because it has to pull the capsule away from a still-accelerating rocket, against a fierce wind blast.
Whether solid rockets are more or less likely to fail than liquid-fuel rockets is debatable. More serious, though, is that when they do fail, it's usually violent and spectacular. So an analysis had to be done: would an escaping Orion be hit by fragments of an exploding SRB?
If the accident occurred during the time of high wind blast – at least the period between 30 and 60 seconds after launch, maybe longer – an escaping Orion wouldn't be able to pull clear of the fragment cloud. Something similar happened in 1998, when a Titan IVA rocket exploded about 40 seconds after launch. It had two somewhat smaller SRBs, but the total load of solid fuel was only a little less than an Ares I SRB, and various other aspects were broadly similar. The debris cloud generated in that accident was half a kilometre across within about 3 seconds, and about 5 km across within about 20 seconds.
But that analysis discovered a much more serious problem, one that nobody had noticed. The big problem is that much of that debris is big chunks of flaming solid fuel, still burning at over 2000 °C. For an accident anywhere in that vulnerable period, Orion will be inside the blazing debris cloud for its whole descent. And its parachutes are nylon, which melts at about 200 °C. They will overheat and disintegrate, and the capsule will crash.
Past experience, on the shuttle and the Titan rockets, suggests that large multi-segment solid rockets have a probability of failure of 0.5 to 1 per cent. Since a failure would be unsurvivable during about a third of the SRB burn time, that puts the chance of losing a crew on each Ares I launch at 0.2 to 0.3 per cent. This is a far higher risk than NASA's modern rules permit.
This problem also affects various other shuttle-derived launch concepts, like the "Direct" scheme advocated by some NASA engineers.
In principle, a still more powerful escape rocket would solve the problem. In practice, the Orion escape rocket is already very powerful, making it very heavy and producing really brutal accelerations if it's activated in milder conditions. Beefing it up still further is probably impractical.
The problem could be avoided by using a different landing system for the capsule. For example, if it landed on rocket thrust instead of parachutes (like the Lunar Lander Challenge vehicles), it wouldn't be so vulnerable to heat.
For another example, there was some study of landing the Apollo capsule with a helicopter rotor rather than parachutes. But such alternatives would require serious redesign of Orion, and significant development work of their own... and today's NASA is reluctant to seriously consider such unorthodox approaches.
Most likely, this problem will be the kiss of death for flying manned spacecraft on large solid rockets. NASA will have to grit its teeth and abandon Ares I, in favour of flying Orion on Delta IV or Atlas V rockets. These rockets, now mostly used to loft communications satellites, come in configurations that use only liquid fuels.
That was arguably a better approach all along... and now it's going to be really hard to do anything else but that. NASA's own rules say that Ares I is impossibly unsafe.