"Heavy lift: examining the requirements"

"Jon S. Berndt" wrote in message
oups.com...
Has an STS SRB ever failed (in flight or in test) "catastrophically"?

No, but the sample size is so small, one cannot say that such an event is
extremely unlikely.

For the STS SRB, human rating _was_ designed in.

Sorry, this isn't true. Early on, there was a requirement for thrust
termination on the SRB's (as opposed to the current destruct charges). This
requirement was not met.

Because of this, you canot shutdown the shuttle SRB's once they start
firing. Even worse, you it is extremely unlikely that a shuttle could
separate from the stack while the SRB's are still firing. I believe others
have said that it would "hang up" on the attachment points, even if the
explosive bolts were fired, so you wouldn't have a clean separation.

Even if you could separate, you'd end up in the (highly abrasive) exhaust
plumes of the SRB's. If you could survive the exhaust plumes, one has to
wonder if the windows on the shuttle would be clear enough that you could
see to land.

If you couldn't see out the front windows, you'd have to hope you're high
enough to bail out successfully (it takes a *long* time to get the entire
crew out the side hatch and the shuttle isn't a very good glider).

All in all, the SRB's don't seem to be very "man friendly", never mind
man-rated (which I'm sure they don't meet current NASA requirements for
man-rating).

Jeff
--
Remove icky phrase from email address to get a valid address.

On 8 Mar 2005 09:10:35 -0800, in a place far, far away, "Jon S.
Berndt" made the phosphor on my monitor glow in such
a way as to indicate that:

Depends on how you define it. Certainly the SRB failure with
Challenger had a catastrophic result, regardless of
how "catastrophic" a failure it was.

Yes the SRB caused the 51-L accident, but if the same failure occurred
with a CEV atop it, hypothetically, it would be a survivable abort
situation. I don't recall reading about any "explosive" type of
failures of the STS SRB in testing.

Not really. More like waivered away.
Again, no one really knows what "human rating" means. I wish that
we could purge the phrase from our vocabulary.

FWIW:

"Human-Rating Requirements, JSC - 28354"
http://www.hq.nasa.gov/office/codea/...documentd.html

And since no vehicle has ever been built (and likely never will) to
those requirements, the phrase remains meaningless and theoretical
only, and vastly misunderstood.

All in all, the SRB's don't seem to be very "man friendly", never
mind man-rated (which I'm sure they don't meet current NASA
requirements for man-rating).

(somewhat tongue-in-cheek): The STS SRBs are flown on a manned vehicle.
Therefore, they are man-rated.

Much of what you describe is not a problem with the SRB (it's just a
booster), but with the STS itself.

Jon

Regarding "Human Rating ..."

Here is a more applicable document. It even deals with thrust
termination issues.

"Human-Rating Requirements and Guidelines for Space Flight Systems"
http://www.aoe.vt.edu/~cdhall/course...8705_0002_.pdf

Jon

Jon S. Berndt wrote:
Do you know offhand how many of the Titan 34D solid boosters have
flown?

There have been a grand total of 121 solid booster powered
Titan launches since 1965. Two more are expected to occur
this year. They will close out the long-running Titan
program.

The Titan record breaks down thusly.

Vehicle Type Launches(Failures)
---------------------------------------
Titan IIIC 36(6)
Titan IIID 22(0)
Titan IIIE 7(1)
Titan 34D 15(3)
Titan 3 Commercial 4(1)
Titan IVA 22(2)
Titan IVB 15(2)*
---------------------------------------
Grand Total 121(15)

* as of 3/8/05 with two more to go

Titan IIIC, D, and E all used 5-segment SRMs. Titan 34D
and Commercial (which was a commercial version of 34D)
used 5.5-segment SRMs. Titan IVA used 7-segment SRMs.
Titan IVB uses 3-segment SRMUs, with much longer segments
of a different design than earlier SRMs.

Two of the failures involved solid rocket motors.
Nine involved upper stage problems. I've provided details
below.

Date Vehicle ID Failure Description Result
----------------------------------------------------------------------
10/15/65 Titan-3C 3C-4 TS fld before 3rd burn;OX leak;tumbled (LEO)
12/21/65 Titan-3C 3C-8 TS 3rd burn fld;stuck OX valve;no sep (GTO)
8/26/66 Titan-3C 3C-12 Early P/L shroud sep;RSO at T+83s FTO
11/6/70 Titan-3C 3C-19 TS last burn failed; unusable orbit (GTO)
2/11/74 Titan-3E 3E-1 Centaur start failed; LOX boost pump FTO
5/20/75 Titan-3C 3C-25 TS guidnce IMU failed, decyd 5/26 (LEO)
3/25/78 Titan-3C 3C-35 2nd stg no start; Rng Safety (RSO) FTO
8/28/85 Titan-34D 34D-7 1st stg shutdown after start;fuel leak FTO
4/18/86 Titan-34D 34D-9 SRM expolded T+16s FTO
9/2/88 Titan-34D 34D-3 TS last burn failed, no GEO (GTO)
3/14/90 Commrcl-T3 CT-2 2nd stg no sep frm Orbus (Titan design)(LEO)
8/2/93 Titan-403A K-11 SRM exploded T+101s FTO
8/12/98 Titan 401A A-20 Expld T+41.3s, Pwr glitch, pitchover FTO
4/9/99 Titan 402B B-27 IUS SRM-2 apogee failed, no SRM-1 sep (GTO)
4/30/99 Titan 401B B-32 Bad Centaur attitude control software (EEO)
----------------------------------------------------------------------

Notes:

TS: Transtage (Hypergolic upper stage manufactured by Martin
(Marietta)
IUS: Intertial Upper Stage (Two-unit solid motor upper stage
manufactured by Boeing)
SRM: segmented Solid Rocket Motor used on Titan 3C, 34D, 4xxA
(manufactured by Alliant)
FTO: Failed to Orbit
(EEO): Unintended Eliptical Earth Orbit
(GTO): Unintended Geosynchronous Transfer Orbit
(LEO): Unintended Low Earth Orbit

- Ed Kyle

No, but the sample size is so small, one cannot say that such
an event is extremely unlikely.

Personally, I don't think I'd characterize a sample size of 226 mission
firings as "small".

Jon

Ed Kyle wrote:

There have been a grand total of 121 solid booster
powered Titan launches since 1965 [with 15 failures].
...
Two of the failures involved solid rocket motors.

It is worth mentioning that before the 34D-9 SRM
failure, 152 SRMs had flown successfully on 76
Titan missions without any problems.

Success can fool you.

(Not much different than what happened to the
U. of Illinois basketball team this year. It was
undefeated and unstoppable - until the last 5
seconds of its regular season).

- Ed Kyle

Ed wrote:

Success can fool you.

That's not exclusive to any one propulsion system though, is it? All
you can do is to have as reliable a system as possible, with failure
modes as benign as possible, to allow a robust abort capability. Add
that the processing of the system (as it relates to safety) should not
be so prohibitively tedious and painstaking that it becomes
unaffordable. Perhaps the STS SRB doesn't best fit the bill - though
IMHO it ought to at least be considered for future use as a cargo
booster component.

[Personally, for getting crews and small payloads to/from orbit, I like
this approach: http://www.stellar-j.com/index.html]

Jon

Ed Kyle wrote:
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.


I would argue that segmented solids with thrust vector control have a
higher failure rate than the liquid engines used in the core stages of
Titan, Delta II, Atlas II and STS during the same period.

I count a premature SSME shutdown and a Titan first stage propulsion
problem, vs. three SRB catastrophic failures on STS and Titan. Am I
missing anything?

Will McLean

Will McLean wrote:

I would argue that segmented solids with thrust vector control have a
higher failure rate than the liquid engines used in the core stages
of
Titan, Delta II, Atlas II and STS during the same period.

I count a premature SSME shutdown and a Titan first stage propulsion
problem, vs. three SRB catastrophic failures on STS and Titan. Am I
missing anything?


Two liquid failures in a combined 234 core
liquid stage cycles (113 STS + 121 Titan)
is a 0.0085 failure rate.

Three solid failures in a combined 468
booster cycles (234*2) is a 0.0064 failure
rate, so solids had a lower realized failure
rate in this comparison.

- Ed Kyle