tneff@dasys1.UUCP (Tom Neff) (09/01/88)
In article <1988Aug29.172104.10823@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >In article <6137@dasys1.UUCP> tneff@dasys1.UUCP (Tom Neff) writes: >>Excuse me, but are we really supposed to believe that omitting the >>flight crew makes using the old SRBs an acceptable risk? > >Rationally, you have a point. Congress is not rational. Losing hardware >is troublesome, but it would not be anything like the political disaster >that more dead astronauts would be. OK, but remember something else I said in the >> article: you don't have to be sitting in the crew module to die in a Shuttle accident. Wouldn't NATO airshows still have gotten the kibosh if all 3 pilots had ejected safely at Ramstein? >>Challenger is >>every bit as "dead" as its crew, and we cannot afford to lose another >>orbiter under any circumstances... > >Then we'll have to ground the shuttle permanently. There is no way to >fly it without risking loss of another orbiter. The NRC report on >shuttle frequency put it even more strongly: if the shuttle continues >flying, another orbiter *WILL* be lost eventually. Yes, but the NRC doesn't really have any better basis for making a statement like that, than NASA does for implying we won't lose one. Sure, if we used the fleet for 30+ years and expanded it to 10 orbiters, losses would be inevitable. They would also be easier to take. What we cannot afford to do is ace one of the remaining three right now. Playing games with unmanned flights for the sake of getting some use out of the flawed-design SRBs strikes me as unwise. (As your AW&ST synopsis noted, I'm hardly alone.) It would certainly tie up Columbia for more months of retrofit downtime, for one thing. And it would introduce another untried component into the system. If we must use the old SRBs, I say let's strap them onto an ELV core and get some iron up there. Our precious orbiter fleet, AND the people who make them go, deserve only the safest hardware available. -- Tom Neff UUCP: ...!cmcl2!phri!dasys1!tneff "None of your toys CIS: 76556,2536 MCI: TNEFF will function..." GEnie: TOMNEFF BIX: t.neff (no kidding)
henry@utzoo.uucp (Henry Spencer) (09/08/88)
In article <6185@dasys1.UUCP> tneff@dasys1.UUCP (Tom Neff) writes: >>... The NRC report on >>shuttle frequency put it even more strongly: if the shuttle continues >>flying, another orbiter *WILL* be lost eventually. > >Yes, but the NRC doesn't really have any better basis for making a >statement like that, than NASA does for implying we won't lose one. Sorry, wrong. NRC justified its predictions in detail. Remember Murphy: betting that things will fail is a whole lot safer than betting that everything will work perfectly. Check out the safety record of segmented solid boosters. Then look at the crash rate for advanced military aircraft. Remember that losing an orbiter does not require another Challenger disaster; possibly the most likely way to lose an orbiter is a landing accident, which might well leave crew and payload intact but damage the orbiter badly enough to make it unflyable. This happens all the time to aircraft. There have been one or two narrow escapes in the shuttle program already, in fact, due to the orbiter's somewhat marginal landing gear. >Sure, if we used the fleet for 30+ years and expanded it to 10 >orbiters, losses would be inevitable. They would also be easier to >take. What we cannot afford to do is ace one of the remaining three >right now... Then, as I said, we must send them to the Smithsonian at once. No matter how careful you are, you cannot fly them without taking risks. If we keep on flying them, even just our present little fleet, losses are inevitable. -- Intel CPUs are not defective, | Henry Spencer at U of Toronto Zoology they just act that way. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
tneff@dasys1.UUCP (Tom Neff) (09/10/88)
In article <1988Sep7.212736.6080@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: > ... possibly the most likely way to lose an orbiter is a landing >accident, which might well leave crew and payload intact but damage the >orbiter badly enough to make it unflyable. Thank you for pointing this out, I really wasn't taking nonfatal "totallings" into account but it's nice to think about ANY kind of shuttle accident (if we are indeed fated to have them) where the crew is OK. >Then, as I said, we must send them to the Smithsonian at once. No matter >how careful you are, you cannot fly them without taking risks. If we keep >on flying them, even just our present little fleet, losses are inevitable. The point you are missing is that your proposed "remedy" is equal in severity to the worst consequences of leaving things unremedied. In other words, if an accident is SOMEDAY inevitable and if such an accident would put the remaining orbiters in the Smithsonian for you anyway, then why jump the gun and do the future accident's work for it immediately, without getting some orbital missions in there first. Just doesn't make sense. (Flight 25's disaster was horrendous, but even it could not erase the manifest for the previous 24 flights!) You are proposing a dichotomy: go back to the old pre-1986 practices or shut everything down immediately. I am saying there is a middle ground: proceed, but more conservatively. Strapping those old SRBs onto our tiny remaining fleet, even unmanned, is just asking for trouble. (Tough to remember but that's what got this conversation started. :-) ) We both agree trouble is inevitable eventually, but I insist we can and should increase the odds in our favor whenever we have a chance. -- Tom Neff UUCP: ...!cmcl2!phri!dasys1!tneff "None of your toys CIS: 76556,2536 MCI: TNEFF will function..." GEnie: TOMNEFF BIX: t.neff (no kidding)
greg@proxftl.UUCP (Gregory N. Hullender) (09/12/88)
In article <1988Sep7.212736.6080@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: [responding to a poster's concern about shuttle safety] >Then, as I said, we must send them to the Smithsonian at once. No matter >how careful you are, you cannot fly them without taking risks. If we keep >on flying them, even just our present little fleet, losses are inevitable. There is no question that there are risks. Nasa certainly doesn't claim that there are none. The concern is over what risk is acceptable. A great number of serious shuttle defects were addressed over the last two and a half years. Also, the policy of launch! launch! launch! (damn the torpedoes! never mind that O-ring!) has finally been laid to rest -- unfortunately together with the Challanger and the remains of its crew. -- Greg Hullender uflorida!novavax!proxftl!greg 3511 NE 22nd Ave / Fort Lauderdale, FL 33308 My opinions are not necessarily those of my employer.
henry@utzoo.uucp (Henry Spencer) (09/13/88)
In article <6377@dasys1.UUCP> tneff@dasys1.UUCP (Tom Neff) writes: >You are proposing a dichotomy: go back to the old pre-1986 practices or >shut everything down immediately. I am saying there is a middle ground: >proceed, but more conservatively... This is in fact what I am suggesting, too. We do not need to go back to 1986 to use the old SRBs; we now know much more about what makes them fail. With a few precautions like restraining bands on the joints, lower leak-test pressures, and a sharp eye on joint temperatures, those old SRBs are not a lot less safe than the new ones. Oh, there is a difference, but given the oxidizer shortage, one has to balance the risks against the utility of being able to fly more missions. That's what I was getting at: given that any shuttle flying involves risks, it is irrational to reject ideas like this without careful consideration of the tradeoffs. Saying "we must reduce risks as much as possible" is silly; we can reduce risks to zero by not flying at all. Tradeoffs are inevitable if we want to get things done. -- NASA is into artificial | Henry Spencer at U of Toronto Zoology stupidity. - Jerry Pournelle | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
tneff@dasys1.UUCP (Tom Neff) (09/17/88)
If we had experience flying the Shuttle unmanned it would be different. As it is, that just looms as another unknown risk factor. -- Tom Neff UUCP: ...!cmcl2!phri!dasys1!tneff "None of your toys CIS: 76556,2536 MCI: TNEFF will function..." GEnie: TOMNEFF BIX: t.neff (no kidding)
johnson@c10sd1.StPaul.NCR.COM (Wayne D. T. Johnson) (09/20/88)
In article <1988Sep13.164340.1289@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: > Oh, there is a difference, >but given the oxidizer shortage, one has to balance the risks against the >utility of being able to fly more missions. Forgive me for asking what might seem to be a dumb question (I'm not as involved with the space program as I once was), but why not remove the oxidizer from the old segments and put it into the new ones? -- Wayne Johnson (Voice) 612-638-7665 NCR Comten, Inc. (E-MAIL) W.Johnson@StPaul.NCR.COM or Roseville MN 55113 johnson@c10sd1.StPaul.NCR.COM These opinions (or spelling) do not necessarily reflect those of NCR Comten.
sw@whuts.UUCP (WARMINK) (09/24/88)
In article <484@c10sd1.StPaul.NCR.COM>, johnson@c10sd1.StPaul.NCR.COM (Wayne D. T. Johnson) writes: > (.....) but why not remove the oxidizer from the > old segments and put it into the new ones? The oxidiser is mixed with the other components of the fuel into a liquid mixture. This liquid is then left to solidify in the appropriate shape for each segment. Extracting the oxidiser from this hard, rubber-based mixture is probably more difficult (if at all possible) than starting from scratch. -- ------------------------------------------------------------------------------ If all statisticians were laid end to end | Stuart Warmink, NAPC across the Atlantic, 99% would drown :-) | <att>!whuts!sw Whippany NJ USA -----------> My opinions are not necessarily those of my employer <-----------
henry@utzoo.uucp (Henry Spencer) (09/24/88)
In article <484@c10sd1.StPaul.NCR.COM> johnson@c10sd1.StPaul.NCR.COM (Wayne D. T. Johnson) writes: >... why not remove the oxidizer from the >old segments and put it into the new ones? Possible in theory; very difficult in practice. It's not the most stable material in the world -- obviously -- and the setting process that occurs after casting is not readily reversible. NASA was originally planning on igniting the old segments under controlled conditions to make the casings available for re-use. As far as I know, there's no other safe way of cleaning them out. -- NASA is into artificial | Henry Spencer at U of Toronto Zoology stupidity. - Jerry Pournelle | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
mjohnson@encad.Wichita.NCR.COM (Mark Johnson) (09/27/88)
In article <1988Sep24.053829.16201@utzoo.uucp>, henry@utzoo.uucp (Henry Spencer) writes: > In article <484@c10sd1.StPaul.NCR.COM> johnson@c10sd1.StPaul.NCR.COM (Wayne D. T. Johnson) writes: > >... why not remove the oxidizer from the > >old segments and put it into the new ones? > > available for re-use. As far as I know, there's no other safe way of > cleaning them out. Why not use the method which the AF and its contractors use to renew the solid propellant in the Minuteman missiles every ten years or so? The motors are cleaned out by the use of a high pressure water jet, which can cut the rubbery perchlorate/polymer material without any ignition risk such as a mechanical cutting tool would entail. Many if not all of the Minuteman birds currently installed in silos have been cleaned out and reloaded this way at least once. It also allows updating the propellant technology to the latest available. Solid fuel mixes have been fairly constant in composition but some advances do take place (higher energy binders, new tricks with combustion accleration/retardation, etc) Fuel for the flames from... -- Mark Johnson (Mark.Johnson@Wichita.NCR.COM) NCR Engineering & Manufacturing-Wichita, KS phone: (316)636-8189 email:...!rutgers!hplabs!hp-sdd!ncr-sd!ncrwic!encad!mjohnson US snailnet: 3718 N. Rock Rd., Wichita, KS 67226
bpendlet@esunix.UUCP (Bob Pendleton) (09/27/88)
From article <484@c10sd1.StPaul.NCR.COM>, by johnson@c10sd1.StPaul.NCR.COM (Wayne D. T. Johnson):
- In article <1988Sep13.164340.1289@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes:
-> Oh, there is a difference,
->but given the oxidizer shortage, one has to balance the risks against the
->utility of being able to fly more missions.
-
- Forgive me for asking what might seem to be a dumb question (I'm not as involved
- with the space program as I once was), but why not remove the oxidizer from the
- old segments and put it into the new ones?
- --
Ever tried to take the egg out of an angel cake? The oxidizer is mixed
into the propellent and then the whole mass is "baked" to form a
solid. Not to mention that in this case the "cake" (solid rocket
propellent) has been known to catch fire and even explode when it is
cut.
Bob P.
--
Bob Pendleton @ Evans & Sutherland
UUCP Address: {decvax,ucbvax,allegra}!decwrl!esunix!bpendlet
Alternate: utah-cs!esunix!bpendlet
I am solely responsible for what I say.