hagens@uwvax.UUCP (02/04/86)
On the news last night (McNeal, Leherer (sp)) two gentlemen
were disagreeing on the safty of a SRB vs. liquid fuel rocket. It
was implied that due to NASA budget restrictions, SRBs were used
when liquid fuel was better/safer.
Whats the scoop on this? Is there any truth to it?
Rob Hagens
--
Rob Hagens @ wisconsin
...!{allegra,heurikon,ihnp4,seismo,sfwin,ucbvax,uwm-evax}!uwvax!hagens
hagens@wisc-rsch.arpamangoe@umcp-cs.UUCP (Charley Wingate) (02/05/86)
In article <615@uwvax.UUCP> hagens@uwvax.UUCP writes: >On the news last night (McNeil, Lehrer) two gentlemen >were disagreeing on the safety of a SRB vs. liquid fuel rocket. It >was implied that due to NASA budget restrictions, SRBs were used >when liquid fuel was better/safer. >Whats the scoop on this? Is there any truth to it? Considering the near-legendary reliability of the all-solids Scout, I find this doubtful. The only novelties about the shuttle SRBs, as far as I know, are their size and the fac that they are made out of segments instead of one piece; the latter has been suggested as contributory to the right SRB failure, but I don't see any reason to accept the allegation that solids are per se less reliable. After all, there is Ariane.... C. Wingate
ins_aeas@jhunix.UUCP (Earle A .Sugar) (02/05/86)
> On the news last night (McNeal, Leherer (sp)) two gentlemen > were disagreeing on the safty of a SRB vs. liquid fuel rocket. It > was implied that due to NASA budget restrictions, SRBs were used > when liquid fuel was better/safer. > > Whats the scoop on this? Is there any truth to it? > > Rob Hagens First, remember that liquid fueled rockets are a much older technology than modern type solid fuel rockets(fireworks notwithstanding). In fact, if I remember my history right, Goddard's rockets were liquid fueled. Liquid fuels are generally volatile (i.e. H2, O2), poisonous (N2O4, CH3NHNH2), or both. They can be unstable at room temperature, require high pressure/low temps to stay liquid, and in general are a pain to handle. Solid fuel, on the other hand, is easy to handle, stable, and generally nontoxic (aluminum powder and ammonium perchlorate), or at least a lot less so than N2O2. The advantage liquid fuel has is that its combustion can be more easily controlled than solid fuel rockets (how does one put a throttle on a roman candle?). As for the asssertion that SRBs were used because of budget constraints, I remember shuttle descriptions included SRBs even in the early 70s when the shuttle was being conceived. At that time, the Air Force was installing solid fueled Minuteman missiles, and their solid fuel rockets were considered the state of the propulsion art, making liquid fueled Titans obsolete. -- ______________________________________________________________________________ Earle A. Sugar Disclaimer:"I doubt anyone else here agrees with me." USENET: ...!seismo!umcp-cs!aplvax!aplcen!jhunix!ins_aeas CSNET:ins_aeas@jhunix.csnet ARPA:ins_aeas%jhunix.csnet@csnet-relay.arpa BITNET: INS_BEAS@JHUVMS (as a last resort) "If you don't expect anything, you'll never be dissappointed." or call 301-889-0815 after 6 P.M. EST
wdm@ecn-pc.UUCP (Tex) (02/06/86)
> >Considering the near-legendary reliability of the all-solids Scout, I find >this doubtful. The only novelties about the shuttle SRBs, as far as I know, >are their size and the fac that they are made out of segments instead of one >piece; the latter has been suggested as contributory to the right SRB >failure, but I don't see any reason to accept the allegation that solids are >per se less reliable. > >After all, there is Ariane.... What exactly is the configuration of Ariane? I keep hearing that one of the stages is solid fueled, but a drawing printed in the Chicago Tribune shows three stages, all liquid fueled. Additionally, is there anything new and novel about the Ariane? From what I have been able to gather, it seems to be pretty mundane rocket. It's major advantage seems to be that it is launched fairly near the equator, and can put satellites out at GEO distances from the Earth.
lmc@cisden.UUCP (Lyle McElhaney) (02/07/86)
> On the news last night (McNeal, Leherer (sp)) two gentlemen > were disagreeing on the safty of a SRB vs. liquid fuel rocket. It > was implied that due to NASA budget restrictions, SRBs were used > when liquid fuel was better/safer. > > Whats the scoop on this? Is there any truth to it? There are several good reasons for using SRB's rather than liquid fueled rockets for the shuttle. The safety factors aside (its very hard to proove anything pro/con there) take a look at the shuttle itself. 75% of the liftoff weight is liquid fuel, used in the most complex and effecient large engines ever made, that represent a large percentage of the cost of both the orbiter and the maintenence/operations budgets. However, at the moment of liftoff, these liquid rockets develop less than 10% of the total thrust requirements of the shuttle; the rest comes from the SRB's. There are several problems with solids; how can you turn them off (you can't, you can only destroy them or let them run out), you can't control closely the thrust developed, they are polluting (compared to the liquids rockets in the shuttle, anyway). But they do deliver, powerfully, reliably, and cheaply. A few other comments about stuff I've read in a marathon session here: The SRBs are slightly maneuverable, are blown away from the ET after separation (after burn-out) by small rockets, and then return to the water on three of the largest parachute systems ever made (I think that the parachute package in the nose of each SRB weighs ~5 tons). Each is filled with a mixture containing aluminum, a latex-like compound, and a perchloride oxidizer. This mixture burns steadily in the open, nothing violent, until it is burned under high pressure. The burning surface of the solid fuel runs nearly the entire length of the SRB, burning from the center outwards toward the shell. The destruct device on each SRB is an externally mounted strip running the length of the SRB on each side, designed to split the casing into two parts lengthwise upon use, thereby destroying both the SRB's aerodynamics (such as it is) and dropping the internal pressure drastically throughout the rocket, effectively killing the thrust of any remaining fuel (which will continue burning). The top one-third of the external tank is a liquid oxygen tank; the bottom two thirds is for liquid hydrogen. Two 17 inch pipes, one from each tank, exit the body of the ET at the bottom of each tank, travel externally down the side of the tank, and then enter the body of the shuttle near the engine pod. This is the *only* source of fuel for the three large rockets; after jettisoning the ET, they are of no use. After jettison, the ET disintegrates in the atmosphere over the Indian Ocean, not reused. There have been studies concerning what it would take to deliver the tank to orbit, for any of several uses. All the other rockets on board the orbiter use hypergolic fuels, which are dangerous (as spelled out here in great detail) but are ideal for use in vacuum; they don't need to be ignited, or forced under pressure, or kept *cold*. Starting and stopping such rockets is simple. The hypergolics aren't as poisonous as many organic poisons, but are very caustic. Challenger was carrying the second tracking and data relay satellite (TDRS), and the Colorado University's Spartan Halley satellite; not Galileo or the telescope. Lyle McElhaney ...hao!contel!lmc
henry@utzoo.UUCP (Henry Spencer) (02/08/86)
> ...was implied that due to NASA budget restrictions, SRBs were used > when liquid fuel was better/safer. Liquid fuel is better in that it gives higher performance and makes prolonged re-use simpler. As for safety, the one important difference is that liquid fuels are much more controllable. Once a solid rocket is lit, there is little you can do except point the exhaust in the right direction and cross your fingers. (Well, one exception: you can stop combustion of some solid fuels by reducing chamber pressure; the only practical way to do this is to blow the nozzle off. Solid- fuel ICBMs do this to get precise cutoff times.) I think NASA's preference was mostly on grounds of performance and re-use. I could be wrong. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry
henry@utzoo.UUCP (Henry Spencer) (02/09/86)
> What exactly is the configuration of Ariane? I keep hearing that one > of the stages is solid fueled, but a drawing printed in the Chicago > Tribune shows three stages, all liquid fueled. The newer Ariane versions have small solid-fuel strap-ons on the sides of the first stage. Otherwise it's all-liquid. > Additionally, is there anything new and novel about the Ariane? From > what I have been able to gather, it seems to be pretty mundane rocket... It *is* a pretty mundane rocket, actually. The equatorial launch site is nice, as is the fact that Ariane is designed to put payloads into a transfer orbit directly rather than needing a separate upper stage for it, but as a rocket it's quite ordinary. The technology is a bit newer than that of the US expendables, but not strikingly so. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry
henry@utzoo.UUCP (Henry Spencer) (02/09/86)
> ...[Liquid fuels] can be unstable > at room temperature, require high pressure/low temps to stay liquid, > and in general are a pain to handle. Solid fuel, on the other hand, > is easy to handle, stable, and generally nontoxic... Don't forget that liquid fuels can be loaded on the pad. NASA used to have an iron-clad rule saying "no fuel in the VAB" [Vertical Assembly Building, since renamed Vehicle Assembly Building]. They were not happy about the shuttle SRBs for this reason. Solid fuel is only *relatively* stable and easy to handle. It remains a fire and explosion hazard. KSC tours used to include the inside of the VAB, but not any more; in fact most non-VAB NASA employees aren't allowed in. > As for the asssertion that SRBs were used because of budget constraints, > I remember shuttle descriptions included SRBs even in the early 70s > when the shuttle was being conceived. Look back a little further and you'll see liquid-fueled boosters. The solids have lower performance, are only semi-reusable, and are not nearly as controllable in flight. NASA almost used a developed Saturn V first stage with wings (the "flyback F-1") as the shuttle booster, but its projected development costs were slightly too high. > At that time, the Air Force > was installing solid fueled Minuteman missiles, and their solid fuel > rockets were considered the state of the propulsion art, making liquid > fueled Titans obsolete. For military applications, requiring years of waiting with minimal or no regular attention, and lightning response to a "launch" command. This is very different from space launches! The USAF wants to keep its ICBMs fully fueled at all times, which greatly changes the safety tradeoffs, and the performance penalty was less significant. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry
lmc@cisden.UUCP (Lyle McElhaney) (02/09/86)
> What exactly is the configuration of Ariane? I keep hearing that one > of the stages is solid fueled, but a drawing printed in the Chicago > Tribune shows three stages, all liquid fueled. > It has three liquid-fuelled stages. The first two stages use hypergolic fuels, the third uses H2/O2 cryogenics. > Additionally, is there anything new and novel about the Ariane? From > what I have been able to gather, it seems to be pretty mundane rocket. > It's major advantage seems to be that it is launched fairly near the > equator, and can put satellites out at GEO distances from the Earth. Nothing novel; just good reliable technology. It can place 1700 Kg at geosync, 4800 Kg at LEO, and 2500 Kg in Sun-synchronous orbit. The shuttle can place 29,500 Kg in LOE. Cost, of course, is another matter, as is launch availability, especially now. Lyle McElhaney ...hao!cisden!lmc
callen@ada-uts.UUCP (02/10/86)
--------------
Considering the near-legendary reliability of the all-solids Scout, I find
this doubtful. The only novelties about the shuttle SRBs, as far as I know,
are their size and the fac that they are made out of segments instead of one
piece; the latter has been suggested as contributory to the right SRB
failure, but I don't see any reason to accept the allegation that solids are
per se less reliable.
--------------
The solid boosters on the Titan IIIc were segmented. The IIIc was also I
VERY reliable vehicle; I'm fairly sure that there was NEVER a failure of
a IIIc.
-- Jerry Callen ...ihnnp4!inmet!ada-uts!callen
P.S. The IIIc was also a GREAT vehicle to watch; I used to live just south
of Cape Canaveral and saw at least a dozen night launches of IIIc's.ems@amdahl.UUCP (ems) (02/10/86)
> First, remember that liquid fueled rockets are a much older technology > than modern type solid fuel rockets(fireworks notwithstanding). In fact, if > I remember my history right, Goddard's rockets were liquid fueled. Liquid > fuels are generally volatile (i.e. H2, O2), poisonous (N2O4, CH3NHNH2), > or both. They can be unstable > at room temperature, require high pressure/low temps to stay liquid, > and in general are a pain to handle. Solid fuel, on the other hand, > is easy to handle, stable, and generally nontoxic (aluminum powder and > ammonium perchlorate), or at least a lot less so than N2O2. The advantage > liquid fuel has is that its combustion can be more easily controlled > than solid fuel rockets (how does one put a throttle on a roman candle?). One way is to have a solid *fuel* rocket, but to valve the oxidizer in as a gas or liquid. I think it has been done before, but don't know the particulars. This is really a hybrid rather than a pure solid rocket, but what the heck. -- E. Michael Smith ...!{hplabs,ihnp4,amd,nsc}!amdahl!ems This is the obligatory disclaimer of everything.
henry@utzoo.UUCP (Henry Spencer) (02/22/86)
> One way is to have a solid *fuel* rocket, but to valve the oxidizer in > as a gas or liquid. I think it has been done before, but don't know > the particulars. This is really a hybrid rather than a pure solid > rocket, but what the heck. The best comment I've heard on hybrid rockets was "hybrid rockets combine all the advantages of solid rockets and liquid rockets, and also all their disadvantages". -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry