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"Heavy lift: examining the requirements"



 
 
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  #11  
Old March 8th 05, 03:27 AM
Murray Anderson
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"Ed Kyle" wrote in message
oups.com...
Jon S. Berndt wrote:
... Considering that (according to the original
article in TSR about SRBs used for a CEV launcher) the concept has

the
support of some in the astronaut office, and that strap-on SRBs would
be used anyway to supplement an Atlas or Delta Medium launcher for

CEV
(according to AvWeek, above), I feel that Dinerman shouldn't have

blown
off the concept so casually.


The overall reliability record is good for solid
boosters, but when they've gone, they've gone
nasty in a hurry. I'm thinking of the Titan 34D
in 1986, of a Titan 4 in the early 90s, and of
the Delta II during the late 90s and a Delta
during the late 70s. These all ended in big
detonations. That is why incorporating them into
manned launchers is so difficult.

Again: which one is safer, a single STS
SRB as a first stage, or a Delta IV or Atlas Medium with several
strap-on SRBs?


Single SRB is statistically more reliable. But is
it safer? Probably. On the other hand, an argument
can be made that neither SRB or EELV with solids
would be safer than an all-liquid system.

The problem with this editorial is that it starts out
arguing for a new heavy-lifter, but ends up talking
about whether solid boosters should be used for
manned launches. It would have been better to keep
the two topics separate.

Few will argue that solids shouldn't be used for
unmanned, heavy-lift launchers. That discussion is
about how big heavy-lifters should be - or whether
they're needed at all.

The solids-for-humans question is an entirely different
problem. The astronaut office is going to have a say
in this one. Right now, if sounds like the majority is
saying "no". It could be that we already have the heavy
launcher (EELV Heavy - just augmenting a little can get
it up to 30 tons to LEO) but that a new or derived
all-liquid Medium is needed to boost the 20 ton-ish CEV.
It could be a matter of adding a second RS-68 or RD-180
to the EELV boosters.

- Ed Kyle


A shuttle SRB would require modification to be used as an ordinary first
stage. At minimum it would need roll control and new guidance software. The
configuration would put a very dense first stage (specific gravity about
1.25) under a large hydrogen-burning upper stage and large payload and
fairing, so the current gimballing system might need hardware modifications
for faster response. You'd need more hydraulic fluid.
The current SRB reliability wouldn't carry over to the new configuration. If
the steering ever failed, you'd need to get the payload away very fast.

Murray Anderson


  #12  
Old March 8th 05, 04:00 AM
Scott Lowther
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Ed Kyle wrote:


The overall reliability record is good for solid
boosters, but when they've gone, they've gone
nasty in a hurry. I'm thinking of the Titan 34D
in 1986, of a Titan 4 in the early 90s, and of
the Delta II during the late 90s and a Delta
during the late 70s. These all ended in big
detonations.

[nerd] NONE of these detonated. [/nerd]


  #13  
Old March 8th 05, 06:14 AM
Jon S. Berndt
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"Ed Kyle" wrote in message

Single SRB is statistically more reliable. But is
it safer? Probably. On the other hand, an argument
can be made that neither SRB or EELV with solids
would be safer than an all-liquid system.


I'm not so sure this one is cut-and-dried, either. Liquid boosters have many
more moving parts. Are they more likely to fail, or to be prematurely shut
down (think of shuttle history)? How does solid propellant act in the most
likely failure scenarios? Liquid propellant?

I remember the Titan SRB failure shortly after 51-L. That one was
spectacular. But the Shuttle SRB seems more robust. Also, in the case of an
axial configuration for launching a CEV, there would presumably be less odd
flexing loads placed on the SRB.

The problem with this editorial is that it starts out
arguing for a new heavy-lifter, but ends up talking
about whether solid boosters should be used for
manned launches. It would have been better to keep
the two topics separate.


Yes, I noticed that, too.

Few will argue that solids shouldn't be used for
unmanned, heavy-lift launchers. That discussion is
about how big heavy-lifters should be - or whether
they're needed at all.


Yep.

The solids-for-humans question is an entirely different
problem. The astronaut office is going to have a say
in this one. Right now, if sounds like the majority is
saying "no".


Why do you say that?

Jon


  #14  
Old March 8th 05, 06:16 AM
Jon S. Berndt
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"Ed Kyle" wrote in message

In addition to the flight safety issues that make
solids a bigger challenge for human launches, there
is a perhaps more important ground safety issue.
Accidents on the ground have killed far more people
than have died in space missions. The presence of
"live" SRBs in the VAB has added cost to the shuttle
program due to safety limitations, for example. A
worst-case fear has long been the unlikely-but-not-
impossible case of an SRB lighting up within the
VAB during processing.


From what I've read, it takes a whole lot to ignite the SRB propellant. Is
this really a concern?

Jon


  #15  
Old March 8th 05, 06:23 AM
Jon S. Berndt
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"Murray Anderson" wrote in message

A shuttle SRB would require modification to be used as an ordinary first
stage. At minimum it would need roll control and new guidance software.

The

Yes, I thought about that, too. Seems to me that roll control could be done
with RCS quads on the CEV "service module" itself, or mounted on the upper
stage?

The current SRB reliability wouldn't carry over to the new configuration.

If
the steering ever failed, you'd need to get the payload away very fast.


It's a problem with any single-engine configuration. With all that weight
out front I'm thinking the stack would be stable enough, CG ahead of CP, to
get away in time. You could also maybe add fins to the SRB. The SRBs work
for the first two minutes, and qbar is high enough to make fins useful
throughout most of the envelope, I'd think.

Jon


  #16  
Old March 8th 05, 12:36 PM
Douglas Holmes
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"Jon S. Berndt" jsb.at.hal-pc-dot.org wrote in message
...
Taylor Dinerman's article in "The Space Review" this morning raised some
questions for me.

1) It did not appear that the question of infrastructure support was
addressed in the article - only the need for heavy lift. A shuttle derived
heavy lift vehicle keeps getting mentioned, but the part that seems to be
ignored is the cost of the supporting workforce, maintaining productions
lines, etc. I haven't yet seen any plausible situation requiring an HLV
to
be launched at regular and frequent intervals that might justify the need
for an HLV. Am I missing something?


NASA seems to want something capable of 55 tons to launch the fuel
to get to the Moon in just one launch. At least one industry study has
indicated
that 55 tons is the ideal size.
Personally I disagree and think 30-35 would work just fine.


2) The idea of using an SRB for a CEV launcher was gently dismissed in the
article with the argument that the SRBs are inherently less safe than
liquid
boosters. Having fired successfully 225 out of 226 times, and with the
single failure (SRB burnthrough) being an abortable failure in the CEV
(possibly even an ATO?), I'd suggest that the SRB has earned some respect.
Regardless, the heavy lift forms of the Delta and Atlas that were
mentioned
also use SRBs, no? Multiple ones? Now, which launcher might be more
reliable?

The concept of using a SRB for a manned rocket just scares me.
No engine out, no health monitoring, no shut down capability.
It violates every rule NASA has set for manned flight.

The Delta and Atlas Heavies use no solids but have no engine out capability.

Based on NASA's proposals I would suggest a 2 engine version of the Atlas
and Delta.
A 2 engine first stage and 2 MB/RL 60 engine second stage.
This would meet almost every requirment NASA is proposing.
It would also allow for future expansion and Heavy Lift in the long term.



  #17  
Old March 8th 05, 01:18 PM
Murray Anderson
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"Jon S. Berndt" jsb.at.hal-pc-dot.org wrote in message
...
"Murray Anderson" wrote in message

A shuttle SRB would require modification to be used as an ordinary first
stage. At minimum it would need roll control and new guidance software.

The

Yes, I thought about that, too. Seems to me that roll control could be

done
with RCS quads on the CEV "service module" itself, or mounted on the upper
stage?

The current SRB reliability wouldn't carry over to the new

configuration.
If
the steering ever failed, you'd need to get the payload away very fast.


It's a problem with any single-engine configuration. With all that weight
out front I'm thinking the stack would be stable enough, CG ahead of CP,

to
get away in time. You could also maybe add fins to the SRB. The SRBs work
for the first two minutes, and qbar is high enough to make fins useful
throughout most of the envelope, I'd think.

Jon


The CG is way behind the CP at least until the SRB is close to burnout.
There isn't all that much weight up front. The specific gravity of a Centaur
upper stage is something like .25 and the payload, including the payload
fairing, is even less dense. Even when the SRB is half burned the CG is 2 or
3 diameters behind the CP.
I'm sure the problems can be worked out, on a cost-plus contract.
Fins would be highly desirable.

Murray Anderson


  #18  
Old March 8th 05, 03:26 PM
Jon S. Berndt
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"Murray Anderson" wrote in message

The CG is way behind the CP at least until the SRB is close to burnout.
There isn't all that much weight up front. The specific gravity of a

Centaur
upper stage is something like .25 and the payload, including the payload
fairing, is even less dense. Even when the SRB is half burned the CG is 2

or
3 diameters behind the CP.


Is the CG really so far behind the CP - and for that long? Where do you get
that data from? Remember 51-L? They _appeared_ neutrally stable, to me, as
they flew from 73 seconds to destruct - for some of that time flying nose
forward into Vinf. Add on an upper stage and a "20 metric ton" CEV and I'd
guess that the CG is ahead of the CP.

Might be an interesting "extra credit" problem for someone ...

Jon


  #19  
Old March 8th 05, 03:46 PM
Ed Kyle
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Jon S. Berndt wrote:
"Ed Kyle" wrote in message

... an argument
can be made that neither SRB or EELV with solids
would be safer than an all-liquid system.


I'm not so sure this one is cut-and-dried, either. Liquid boosters

have many
more moving parts. Are they more likely to fail, or to be prematurely

shut
down (think of shuttle history)? How does solid propellant act in the

most
likely failure scenarios? Liquid propellant?


Liquid boosters have a slightly higher failure rate,
but they may still be safer for crewed flight because
their failure modes are more benign. This would make
escape systems more likely to succeed.

The solids-for-humans question is an entirely different
problem. The astronaut office is going to have a say
in this one. Right now, if sounds like the majority is
saying "no".


Why do you say that?


The AWST article included these paragraphs.

"The Astronaut Office at the Johnson Space Center is not keen
on any of these options (AW&ST June 14, 2004, p. 15). The
astronauts have taken a position that "human rating should be
designed in, not appended on." The Office is calling for an
order of magnitude reduction in the risk of fatalities on
ascent, and has expressed concern that an EELV--be it Delta
or Atlas--may not be safe enough even with upgrades."

" ...The concern in part is due to the potential for rare,
but instantaneously catastrophic, failure modes inherent with
solid rocket boosters on the medium options for both Atlas and
Delta EELVs. Such failure modes would be difficult for an
advanced health-monitoring system to catch before loss of
control to separate the CEV safely."

- Ed Kyle

  #20  
Old March 8th 05, 03:58 PM
Ed Kyle
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Scott Lowther wrote:
Ed Kyle wrote:


The overall reliability record is good for solid
boosters, but when they've gone, they've gone
nasty in a hurry. I'm thinking of the Titan 34D
in 1986, of a Titan 4 in the early 90s, and of
the Delta II during the late 90s and a Delta
during the late 70s. These all ended in big
detonations.

[nerd] NONE of these detonated. [/nerd]


Sure they did, when the range safety systems
initiated. The dictonary says that a detonation
is "the act of detonating an explosive".

Irregardless, solids have, as AW&ST put it, "rare,
but instantaneously catastrophic, failure modes"
that liquids do not have. These flights demonstrated
some of "instantaneously catastrophic" modes.

- Ed Kyle

 




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