Will this kill Ares?

http://www.newscientist.com/blogs/sh...-ares-roc.html

Read the comments as to its applicability to DIRECT.

Frogwatch wrote:
http://www.newscientist.com/blogs/sh...-ares-roc.html

Read the comments as to its applicability to DIRECT.


"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."

Then we had better stop launching shuttles immediately, as they have no
ascent escape system and _two_ SRBs on them.

Pat

Pat Flannery wrote:


Frogwatch wrote:
http://www.newscientist.com/blogs/sh...-ares-roc.html


Read the comments as to its applicability to DIRECT.


"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."

Then we had better stop launching shuttles immediately, as they have no
ascent escape system and _two_ SRBs on them.

That's acceptable risk for a legacy system with only ten more flights
over the next few years, but unacceptable in any new *manned* designs.

Pat

"Pat Flannery" wrote in message
dakotatelephone...


Frogwatch wrote:
http://www.newscientist.com/blogs/sh...-ares-roc.html

Read the comments as to its applicability to DIRECT.


"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."

Then we had better stop launching shuttles immediately, as they have no
ascent escape system and _two_ SRBs on them.

That's not the point, everyone knows shuttle has a demonstrated reliability
far lower than intended. This is one of the big reasons it's being retired.

The problem is that NASA's paper rocket, Ares I, looked to be a bit safer
than the alternatives. Unfortunately, as development progresses, its
predicted reliability has fallen, and will likely continue to fall, as more
unknowns become knowns.

As for this particular problem, large, segmented, solid rocket boosters have
some pretty severe failure modes. Their failure modes tend to develop
quickly, without warning, and tend to be catastrophic in the extreme.
Liquids, on the other hand, tend to cost more to develop, but generally have
more benign failure modes (often times, failing engines can be shut down).
And even when they do fail catastrophically, like a turbine failure which
sends shrapnel through adjacent engines, their failure still isn't quite as
catastrophic as that of a solid rocket booster case rupture.

Post Challenger, it's always been my opinion that large, segmented, solid
rocket boosters should be avoided in launch vehicle design. The data tends
to back up that opinion.

Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon

On Jul 24, 7:55�am, "Jeff Findley"
wrote:
"Pat Flannery" wrote in message

dakotatelephone...







Frogwatch wrote:
http://www.newscientist.com/blogs/sh...9/07/death-kne....

Read the comments as to its applicability to DIRECT.

"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."

Then we had better stop launching shuttles immediately, as they have no
ascent escape system and _two_ SRBs on them.

That's not the point, everyone knows shuttle has a demonstrated reliability
far lower than intended. �This is one of the big reasons it's being retired.

The problem is that NASA's paper rocket, Ares I, looked to be a bit safer
than the alternatives. �Unfortunately, as development progresses, its
predicted reliability has fallen, and will likely continue to fall, as more
unknowns become knowns.

As for this particular problem, large, segmented, solid rocket boosters have
some pretty severe failure modes. �Their failure modes tend to develop
quickly, without warning, and tend to be catastrophic in the extreme.
Liquids, on the other hand, tend to cost more to develop, but generally have
more benign failure modes (often times, failing engines can be shut down)..
And even when they do fail catastrophically, like a turbine failure which
sends shrapnel through adjacent engines, their failure still isn't quite as
catastrophic as that of a solid rocket booster case rupture.

Post Challenger, it's always been my opinion that large, segmented, solid
rocket boosters should be avoided in launch vehicle design. �The data tends
to back up that opinion.

Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon- Hide quoted text -

- Show quoted text -

given the costs of todays satellites even unmanned solid boosters
should probably be avoided.

anyone look at the rising costs and complexity of the latests
satellites....