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How many shuttle flights per year without Challenger accident?



 
 
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  #1  
Old February 10th 12, 10:15 AM posted to sci.space.history
Yeechang Lee
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Posts: 3
Default How many shuttle flights per year without Challenger accident?

In retrospect we know that the O-ring issue that destroyed Challenger
was inevitable. It had almost happened in earlier flights and would
likely have happened on some winter day sooner or later. That said,
let's say it doesn't ever happen. Maybe because it's diagnosed, or
NASA and Thiokol listen to Boisjoly and require a certain outside
temperature for launches, or NASA just never schedules a launch on
that cold a day.

Without Challenger, shuttles would have continued to carry commercial
and DoD payloads. Discovery would be dedicated to SLC-6
launches. Additional American politicians are likely shuttle
passengers, as well as senior military leaders like Pete Aldridge and
more foreign dignitaries (Prince Andrew, perhaps?). The
Journalist-in-Space program would have joined Teacher-in-Space;
Artist-in-Space was likely next, and perhaps Writer-in-Space and even
Boy Scout-in-Space. In such a scenario it seems more likely than not
that Dennis Tito would have been able to persuade NASA to take him up,
and quite possibly for a price more akin to the $40,000 McDonnell
Douglas paid for each of Charles Walker's three flights rather than
the $20 million to Russia.

NASA flew nine shuttle flights in 1985, a rate it would never hit
again although it flew eight per year several times in the
1990s. Without losing Challenger, how many flights could NASA have
expected to have flown a year? I understand it was contemplating
perhaps two dozen a year with the four shuttles; was such a pace
feasible? If not that many, a dozen? 15? Would the agency order a
fifth shuttle with such demand?

--
URL:http://www.pobox.com/~ylee/ PERTH ---- *
  #2  
Old February 10th 12, 03:48 PM posted to sci.space.history
Bob Haller
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Posts: 3,197
Default How many shuttle flights per year without Challenger accident?

On Feb 10, 4:15*am, Yeechang Lee wrote:
In retrospect we know that the O-ring issue that destroyed Challenger
was inevitable. It had almost happened in earlier flights and would
likely have happened on some winter day sooner or later. That said,
let's say it doesn't ever happen. Maybe because it's diagnosed, or
NASA and Thiokol listen to Boisjoly and require a certain outside
temperature for launches, or NASA just never schedules a launch on
that cold a day.

Without Challenger, shuttles would have continued to carry commercial
and DoD payloads. Discovery would be dedicated to SLC-6
launches. Additional American politicians are likely shuttle
passengers, as well as senior military leaders like Pete Aldridge and
more foreign dignitaries (Prince Andrew, perhaps?). The
Journalist-in-Space program would have joined Teacher-in-Space;
Artist-in-Space was likely next, and perhaps Writer-in-Space and even
Boy Scout-in-Space. In such a scenario it seems more likely than not
that Dennis Tito would have been able to persuade NASA to take him up,
and quite possibly for a price more akin to the $40,000 McDonnell
Douglas paid for each of Charles Walker's three flights rather than
the $20 million to Russia.

NASA flew nine shuttle flights in 1985, a rate it would never hit
again although it flew eight per year several times in the
1990s. Without losing Challenger, how many flights could NASA have
expected to have flown a year? I understand it was contemplating
perhaps two dozen a year with the four shuttles; was such a pace
feasible? If not that many, a dozen? 15? Would the agency order a
fifth shuttle with such demand?

--
URL:http://www.pobox.com/~ylee/ * * * * * * * * *PERTH ---- *


it might have been a wonderful experience. as long as a high flight
rate didnt cause a different loss. i think that should be the premise
of your question.

without any major accident what could the flight rate have been?

i seem to rember post challenger findings of lots of killer type
issues being found and fixed. perhaps like apollo one a accident
improved the program?
  #3  
Old February 11th 12, 03:56 AM posted to sci.space.history
Brian Thorn[_2_]
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Posts: 2,266
Default How many shuttle flights per year without Challenger accident?

On 2012-02-10 09:15:13 +0000, Yeechang Lee said:

In retrospect we know that the O-ring issue that destroyed Challenger
was inevitable. It had almost happened in earlier flights and would
likely have happened on some winter day sooner or later. That said,
let's say it doesn't ever happen. Maybe because it's diagnosed, or
NASA and Thiokol listen to Boisjoly and require a certain outside
temperature for launches, or NASA just never schedules a launch on
that cold a day.


The relatively simple joint heaters would have been enough to resume
flying while the field joint was redesigned, I think.

NASA flew nine shuttle flights in 1985,


…and came 15 seconds away from a tenth on December 18, 1985.

a rate it would never hit
again although it flew eight per year several times in the
1990s. Without losing Challenger, how many flights could NASA have
expected to have flown a year?


If Challenger had not been destroyed (say, the windshear did not cause
the leak to reopen at altitude), and the severe damage of the o-rings
was found after SRB recovery, this should have been sufficient for
Thiokol's engineers to effectivdely force a moratorium on Shuttle
launches until the joint heaters could be implemented, resuming flying
say in 1987. During that time, the Shuttle program could well have
caught its breath and built up a stockpile of spare parts that would
have made meeting the flight rate somewhat easier (this was done after
Challenger.) I think realistically the program would have topped out
around 15-16 per year, 12 from KSC and 3 or 4 from SLC-6.

I understand it was contemplating
perhaps two dozen a year with the four shuttles; was such a pace
feasible?


No. External Tank production would probably have peaked around 18 per
year. Michoud could handle a little more, but I doubt they would have
really pushed that hard. They'd have reduced the flight rate to keep
things under control.

If not that many, a dozen? 15?


Probably, if they funded a third OPF at KSC (without sacrificing SLC-6.)

Would the agency order a
fifth shuttle with such demand?


No, they would have backed out of the commercial market anyway,
relieving pressure on the 24-per-year goal. Arianespace would have
taken more commercial payloads regardless of Challenger.

Brian

  #4  
Old February 11th 12, 07:44 PM posted to sci.space.history
Val Kraut
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Posts: 329
Default How many shuttle flights per year without Challenger accident?


"If not that many, a dozen? 15? Would the agency order a
fifth shuttle with such demand?


Someplace I have a zerox of a US Senate Letter detailing the proposed
Shuttle Capabilities - $10M per launch, 2 week turnaround, 66 launches a
year. Sixty Six launches a year means Florida's weather would have had to
really cooperate. There were artists pictures of shuttles being loaded by a
crane and three ground crew. Just like a 474 freighter going out of Kennedy
Airport. Everything would go up on shuttles, They never came close. The Air
Force was to have two dedicated vehicles, which were never built as they
ducked out of the program partially blaming serious faults at SLC-6 that had
been incorporated to keep the environmentalists happy, and finally the
Challenger disaster that really denied them required access to space. The
Titan IV motto was "Assured Access to Space". The shuttle program was doomed
from the start by the great expectations of our politicians who wouldn't
spend the real dollars required and a NASA who went along.

But even if all went well as planned, Enterprise was refurbished for space
(but is was too heavy), NASA bought 1 more and the Air Force Bought 2, and
Challenger didn't explode - so you'd only have about twice as many - all
with the same faults.
Val Kraut


  #5  
Old February 11th 12, 07:53 PM posted to sci.space.history
Val Kraut
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Posts: 329
Default How many shuttle flights per year without Challenger accident?


" In retrospect we know that the O-ring issue that destroyed Challenger
was inevitable. It had almost happened in earlier flights and would
likely have happened on some winter day sooner or later.


Supposedly there were partial burn throughs on recovered boosters - but NASA
didn't wake up to the real potential until they actually lost a vehicle.
There was an interesting article on the mind set people get into - Hey
worked the last 24 times we did it - we're on a roll!

And on Colombia, some said let's get one of the Recon birds to look at the
tiles - and again it was dismissed.

Go back and look at how long some satellites sat at SLC-4 being proscessed -
this itself would have impacted the same satellites if they were launched at
SLC-6

Val Kraut


  #6  
Old February 11th 12, 09:55 PM posted to sci.space.history
Brian Thorn[_2_]
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Posts: 2,266
Default How many shuttle flights per year without Challenger accident?

On 2012-02-11 18:44:14 +0000, Val Kraut said:

"If not that many, a dozen? 15? Would the agency order a
fifth shuttle with such demand?


Someplace I have a zerox of a US Senate Letter detailing the proposed
Shuttle Capabilities - $10M per launch, 2 week turnaround, 66 launches
a year.


I've never seen a reference to more than 50 launches per year, which
was (and still is) widely reported as "almost once a week". But even 50
was impossible with the Shuttle design and infrastructure as it was
actually built, because Michould could crank out no more than 20-22
External Tanks per year, so there were certainly never serious plans
for once-a-week flights. This is all perfectly acceptable, because
there was never the slightest chance there would be more than 50
payloads per year requiring launches, nevermind two or three payloads
on each of those 50 launches. Even if Ariane had never gotten a
foothold.

Getting a good read on how many Shuttle Orbiters NASA wanted, and when,
is pretty hard. Numbers ranged from 10 to 4. But once construction
started, NASA had to fight just to get four Orbiters. Discovery and
Atlantis were not finally approved until late 1979, the threat of not
getting the lighter Discovery and Atlantis drove the decision to
upgrade STA-099 instead of OV-101 as the second spaceworthy Orbiter.


But even if all went well as planned, Enterprise was refurbished for
space (but is was too heavy),


Enterprise would have been about the same as Columbia, maybe a little
lighter. It could easily have handled Spacelab and HS-376 deployment
missions, just as Columbia did. And note that despite being the
heaviest Orbiter, Columbia actually launched the heaviest payload of
the Shuttle program: the Chandra AXAF/IUS. But everything useful was
yanked out of Enterprise and installed in Challenger, so there really
was no point to refurbishing Enterprise once the decision was made to
move to STA-099 (renamed OV-099 Challenger) in 1978.

  #7  
Old February 12th 12, 07:33 AM posted to sci.space.history
Val Kraut
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Posts: 329
Default How many shuttle flights per year without Challenger accident?


I've never seen a reference to more than 50 launches per year, which
was (and still is) widely reported as "almost once a week". But even 50
was impossible with the Shuttle design and infrastructure as it was
actually built, because Michould could crank out no more than 20-22
External Tanks per year, so there were certainly never serious plans for
once-a-week flights. This is all perfectly acceptable, because there was
never the slightest chance there would be more than 50 payloads per year
requiring launches, nevermind two or three payloads

You have to remember the early dreams of shuttle utilization that included
much more manned operation and things like large space structures, beam
builders, orbiting power stations etc that were being seriously studied at
the time. The Shuttle was supposed to privide really cheap access for major
new space programs. Grumman, as an example, actually had a working prototype
beam builder that would ride in the shuttle bay and extrude and spot weld
long lightweight beam assemblies.

Val Kraut


  #8  
Old February 12th 12, 06:38 PM posted to sci.space.history
Brian Thorn[_2_]
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Posts: 2,266
Default How many shuttle flights per year without Challenger accident?

On 2012-02-11 18:53:22 +0000, Val Kraut said:

" In retrospect we know that the O-ring issue that destroyed Challenger
was inevitable. It had almost happened in earlier flights and would
likely have happened on some winter day sooner or later.


Supposedly there were partial burn throughs on recovered boosters - but
NASA didn't wake up to the real potential until they actually lost a
vehicle. There was an interesting article on the mind set people get
into - Hey worked the last 24 times we did it - we're on a roll!


Not "supposedly", it is well documented. My point is that STS-51L
nearly got away with it. The o-ring failure did not cause the disaster
alone. Had the windshear at T+55 seconds or so not reopened the leak
(this was the strongest windshear the Shuttle has ever experienced,
before or after Challenger), Challenger might have squeaked by and
survived. But that level of damage, with *both* o-rings having failed
(a first) would certainly have given the engineers the ammunition they
needed to suspend flights until a fix could be implemented. NASA would
have screamed bloody murder about missing the Galileo and ISPM
deadlines, but they would have been out of their "the backups kept us
safe" counter-arguments. The engineers would finally have their
evidence that the design was unsafe, which is what they didn't have in
hand on the night of January 27-28, 1986.

An interesting what-if.

Brian

  #9  
Old February 14th 12, 12:47 AM posted to sci.space.history
David Spain
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Posts: 2,901
Default How many shuttle flights per year without Challenger accident?

Brian Thorn wrote:
Not "supposedly", it is well documented. My point is that STS-51L nearly
got away with it. The o-ring failure did not cause the disaster alone.
Had the windshear at T+55 seconds or so not reopened the leak (this was
the strongest windshear the Shuttle has ever experienced, before or
after Challenger), Challenger might have squeaked by and survived. But
that level of damage, with *both* o-rings having failed (a first) would
certainly have given the engineers the ammunition they needed to suspend
flights until a fix could be implemented.


The other possibility, Thiokol could have stuck to their guns about not
launching in under 51 deg F conditions. 51-L would have been delayed a few
days until the weather warmed up, then they might not have had any O-ring
failures. NASA and Thiokol might have continued operating within uncertain
zones of reliability until the next time a limit was pushed.

However IIRC, the joint design was under review and a parallel effort was
underway to fix it. It is an interesting speculation that had Thiokol
management stood by their engineer's original higher temperature limit
recommendation at the telecon, if that alone would have been enough to buy
enough time to allow the fix to be implemented w/o a disaster.

Given the NASA mindset at the time however, it seems likely it would have just
moved the Crit-1 failure from SRB case joints to somewhere else.

Dave
  #10  
Old February 14th 12, 08:06 PM posted to sci.space.history
Mike DiCenso
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Posts: 150
Default How many shuttle flights per year without Challenger accident?

On Feb 10, 7:56*pm, Brian Thorn wrote:
On 2012-02-10 09:15:13 +0000, Yeechang Lee said:

In retrospect we know that the O-ring issue that destroyed Challenger
was inevitable. It had almost happened in earlier flights and would
likely have happened on some winter day sooner or later. That said,
let's say it doesn't ever happen. Maybe because it's diagnosed, or
NASA and Thiokol listen to Boisjoly and require a certain outside
temperature for launches, or NASA just never schedules a launch on
that cold a day.


The relatively simple joint heaters would have been enough to resume
flying while the field joint was redesigned, I think.

NASA flew nine shuttle flights in 1985,


…and came 15 seconds away from a tenth on December 18, 1985.


In calender year terms, Brian. They actually flew 10 missions within a
one year span from STS-51-C launched on January 24, 1985 to STS-61-C
which launched January 12, 1986. Had STS-51-L not been delayed by
STS-61-C, it would have been 11 in 12 months, and Challenger would
have been launched in warmer weather, thus a launch failure would not
likely have occurred.

Also along similar thinking; Discovery, which launched four times in
1985, actually had launched six times in a one year period from first
flight on August 30, 1984 to it's last pre-Challenger flight on August
27, 1985. So theoretically you could have orbiters doing 4-6 flights a
year, if dedicated OPFs were available. Say one OPF at Vandenburg, and
three at KSC, which allows all four vehicles to be processed
simultaneously. That means between 12 and 18 flights a year, if ET and
SRB production and processing permits it. Atlantis between STS-51-J
and and STS-61-B had demonstrated a 55 day turnaround between flights
(45 days minus the days lost by ferrying Atlantis between Edwards and
KSC), so ramping up to 7 flights for one orbiter was theoretically
doable back then. Columbia probably would never be able to manage more
than 4-5 flights a year given her history of being chronically
stricken with technical issues compared to the other orbiters.

a rate it would never hit
again although it flew eight per year several times in the
1990s. Without losing Challenger, how many flights could NASA have
expected to have flown a year?


If Challenger had not been destroyed (say, the windshear did not cause
the leak to reopen at altitude), and the severe damage of the o-rings
was found after SRB recovery, this should have been sufficient for
Thiokol's engineers to effectively force a moratorium on Shuttle
launches until the joint heaters could be implemented, resuming flying
say in 1987. During that time, the Shuttle program could well have
caught its breath and built up a stockpile of spare parts that would
have made meeting the flight rate somewhat easier (this was done after
Challenger.) I think realistically the program would have topped out
around 15-16 per year, 12 from KSC and 3 or 4 from SLC-6.


Agreed, though SLC-6 would have likely put a huge damper on things for
a while once the actual fueled testing of Columbia at that facility
revealed the flaws there.

*I understand it was contemplating
perhaps two dozen a year with the four shuttles; was such a pace
feasible?


No. External Tank production would probably have peaked around 18 per
year. Michoud could handle *a little more, but I doubt they would have
really pushed that hard. They'd have reduced the flight rate to keep
things under control.


They'd have had no choice, looking back on it. There were other
technical issues that would have forced delays or flight rate
reduction or caused a catastrophic loss.

*If not that many, a dozen? 15?


Probably, if they funded a third OPF at KSC (without sacrificing SLC-6.)

Would the agency order a
fifth shuttle with such demand?


No, they would have backed out of the commercial market anyway,
relieving pressure on the 24-per-year goal. Arianespace would have
taken more commercial payloads regardless of Challenger.


Why? STS had huge cargo capacity for most of the then existing
satellite classes. Just load up a bunch of satellites into one mission
as was done for STS-41-D.
-Mike
 




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