Thomas1195 wrote:
Marathag wrote:
Certain companies had capabilities and while the majority lagged some had, as marathag puts it, their act together but funding and changing research requirements meant they fell behind in certain areas. In specific to what I was addressing Blue Steel for example had to have 'valve' driven guidance and control with all that implied for power and support systems. Couple that with the various missteps and blind alleys and overall lack of funding...
As for design I'd note that the British, (unlike almost everyone else) were comfortable and worked well with HTP which due to density and average ISP was comparable with kerolox for such applications. HTP stages tended to be more compact and somewhat lighter mass for the volume due to no cryogenic liquids. They also tended to be more robust by default, (see Black Arrow here: https://en.wikipedia.org/wiki/Black_Arrow, specifically this photo of a 'landed' BA stage; https://en.wikipedia.org/wiki/Black_Arrow#/media/File:Black_Arrow_R3_Stage_1.JPG) which has always made me wonder what recovery would be like.
Had the Gamma motors been replaced with the large chamber Stentor motors and an enlarged tankage system, (see: http://www.spaceuk.org/ba/siddeley.htm) with a Black Knight second stage and to-be-designed HTP third stage would have given the British a "Thor-Delta" class launcher in the early 60s. Adding strap-on solid, (as America did with various versions of the Thor/Delta over the years) would have increased the payload as would have the continued development of hyrdolox upper stages (http://www.spaceuk.org/hydrogen/hydrogen.htm) which had been undertaken by Saunders Roe, (http://www.spaceuk.org/hydrogen/SP510.htm) Roll Royce/Bristol Siddeley, (http://www.spaceuk.org/hydrogen/rr.htm) and of course the RAE, (http://www.spaceuk.org/hydrogen/TechNoteSpace30.htm, http://www.spaceuk.org/hydrogen/TN30.htm) which all proposed and/or studied, (and tested) various engines.
The British were aware of and had early interest in hydrolox engines: http://www.spaceuk.org/hydrogen/hggr.htm
Or course in OTL Black Arrow wouldn't be ready until the late 60s and work on hydrolox ground to a halt with the end of ELDO and by 1962 the US Centaur stage was 'available' for use. But consider for a moment that the British actually had a 'leap' of about two years (@1954 for UK and @1956 for the US though the IDEA has been there prior to in the general community) in interest and study for hydrolox propulsion.
Phx1138 wrote:
It depends on the application actually. For example JP was concerned with high-ISP through the majority of the flight trajectory mostly because he was focused on Single Stage To Orbit and going with the 'conventional-wisdom' of the time therefore assumed hydrolox propellant.
Quite obviously hydrolox gives the highest practical ISP, (note that as there have been studies and designs which used everything from fluorine to "high-density-particulate-materials" as additives to boost that ISP with little regard to actual practicality or utility) of 'standard' chemical propulsion so it is favored but it has enough drawbacks as well, (density, deep-cryogenic temps, etc) that alternatives and 'cheats' cropped up early on.
Duel-fuel, (burning something 'dense' and lower ISP to start and switching to pure LH2 later on) 1.5-STO and 'booster' or "zero-stage" designs have all been suggested but the core of 'purest' SSTO-advocates, (much like the purest Scramjet advocates) consider anything LESS than a 'pure' SSTO as a waste of time and effort. This tends to reflect in any efforts to study any propellant combination with LESS ISP than hydrolox which despite the 'math' working out, (despite studies showing that SSTO is possible with kerolox, keroxide, and methalox the number of studies that specify and defend hydrolox as the only acceptable propellant combo pretty much bury the alternatives) is not given much credence in general discussion.
(This despite two of the main 'examples' of the possibility of SSTO vehicles, the Titan-II first stage, and Atlas, did not in fact use hydrolox propellant)
As fasquadron noted chasing ISP can, and has been, a "Red Queen's Race" beyond a certain point. There was literally a point where all the 'experts' were touting all the fantastic advantages that would be available as soon as "we have hydrogen engines" without addressing, (or even acknowledging) the numerous issues. It has become quite obvious that LH2 as a booster propellant is lacking in efficiency and as it requires a 'boost' to get moving, (there's a reason the Delta-IV/IV Heavy takes a while to get off the pad without solid boosters AND a reason the Delta-IV was to be replaced by the Atlas V and now the Vulcan) otherwise it wastes propellant.
Fasquadron wrote:
Not really the former as oil stocks are stable and there are known sources we've not tapped yet even assuming we don't start 'making' oil from other sources. (Turning coal into 'oil' is still only marginally cost effective but has the distinct advantage of removing almost all the Sulphur and other 'pollutants' in it making it almost as clean a natural gas) The current abundance of natural gas, (which is mostly methane) seems to be what is the main spur to current use of liquid methane though possible 'off-planet' sourcing is often cited. Truth is making methane off-planet is by far one of the least efficient propellants to make ranking only a bit below simpler to make, (but more difficult to store, but not THAT difficult) liquid hydrogen. The other main driver is that the design differences between a methalox and hydrolox engine are very few and the possibility of using existing designs of the latter to build the former are high. (In fact we know that the RL10 can run on methalox with modification and the J2 was studied to do so)
Fscott wrote:
All the above on this one
Thrust oscillation and differences due to grain, mixture and curing is a big problem especially as the overall size gets larger. Overall ISP of a solid is usually lower than that of a liquid though for their usual use, (high thrust, short duration, usually a booster) this isn't as much of an issue but once you get into second, third or even fourth stages their utility diminishes greatly. (As a final or insertion stage they have some advantages but if you have a choice liquids are still better)
For example the four stage Scout (https://en.wikipedia.org/wiki/Scout_(rocket_family) could by the end put up a 210kg/463lb payload, the basic Thor-Able/Ablestar could do half that in two stages and Thor-Agena, Thrust Augmented Thor, and Thor-Delta well over twice that. Solids were initially seen as more cost effective than liquids but as size grew so did cost in a non-linear/non-intuitive manner. Once you move beyond strictly military requirements of long-term storability and quick response solids are far less useful outside the realm of booster applications. About the only way they become significantly 'cost-effective' is if the user gets them at a high discount or surplus. Athena, Minotaur/Taurus, Vega, and Conestoga for examples all relied on government surplus "missile" motors or subsides to show competitive costs. Pegasus costs by all estimations should have been much lower than they were but part of the reason this wasn't true was that the solid motors were all specially designed and constructed for the vehicle. Adding a surplus Peacekeeper stage and later adapting surplus Minuteman II stages was a method of increasing payload and lowering costs but once the supply was gone...
Getting off-topic but specifically in the case of Pegasus an independent design suggestion known as Pogo or JELAC, (Jet Engine Launch Assist Concept) replaced the sub-sonic carrier aircraft with a 'booster' using 4 F100 jet engines that took off vertically, staged around Mach-3/4 and about 80Kft then returned to a vertical landing to be reused. Due to the mass reduction, (no wings or tail surfaces to carry or joining structure) payload of a 'basic' Pegasus rose to the level of the later Pegasus XL. A Pegasus XL version put more payload on-orbit than it was designed to handle. Adding a ramjet, (not Scramjet) second stage to around Mach-5/6 doubled the payload. It's hard to find information to link to these days since Glenn Olson's alt.accel.com shut down (about 2010-ish IIRC) but NASA Dryden patented and advertised a 'similar' (with no noting of 'prior art') concept called "Ram-Booster" which used F100s and a ramjet second stage with a Centaur based third stage. "Prior art" would include a study done by Dani Eder of Boing in the mid-70s which didn't use a ramjet but used ten F100s in individual recoverable pods to boost a hydrolox RL10 powered TSTO into orbit with a 6Klb payload to LEO.
Like I said a bit off-topic but if we can assume better economics and some 'sense' in the right places I think British post-WWII aviation and rocketry could have been very different.
Bolt451 wrote:
Black Arrow though it didn't fly till 28 October, 1971 by which time 'better' launchers were available. Blue Streak was the basis of the ELDO launch vehicle and Blue Streak pretty much worked every flight but the entire launcher (Europa) was too small to be of continued interest even the 'augmented' version proposed: http://www.spaceuk.org/bstreak/eldo/augmented.html
Interestingly enough the estimated payload of the LRB version was twice that of the SRB version
The proposed all-British Black Prince LV, (http://www.spaceuk.org/bstreak/bs/bsslv.htm) would have been about equal to Atlas Agena in basic capability. Adding a higher ISP second and third stage would have given something comparable to Atlas Centaur but...
(Hawker Siddeley made a pitch in 1972 to mate the Blue Streak with a Centaur upper stage, payloads to GTO ranged from 650kg up to 1050kg with four SRBs. See: http://www.spaceuk.org/bstreak/bs/bs_centaur.html)
Two alternate Black Arrow designs were put forward, (http://www.spaceuk.org/ba/siddeley.htm) using the bigger Stentor chambers from the Blue Steel instead of the Gamma's and a Black Knight based HTP upper stage. Payload to LEO was somewhere around 650+lbs. Strap-on boosters and a different propellant (higher ISP) for the upper stage is possible. In 1971 an upgraded Black Arrow called SLAVE, (Satellite LAunch VEhicle, really? Can't just go for "SLV" and avoid the issues?) was proposed but obviously not pursued.
Strangely enough a propellant combination that cropped up during RL10 testing, (I swear that engine has probably been run on alcohol or maybe just the test engineers were ) but Propane, cryo-cooled to around LOX storage temps, densifies to around that of kerosene, (aka will fit into the same space/tanks if you add some external insulation) and cryo-propane/LOX gives performance close to that of methalox. (@110% that of kerolox/@80% that of hydrolox)
Now have someone make note of the fact that HTP does not in fact decompose spontaneously when cooled to around 41F/5C, (note that's AC cool instead of cryogenic cool like LOX requires) which the US stumbled upon in the late 70s and you get some interesting possible paths.
Randy[/quote]
Marathag wrote:
Certain companies had capabilities and while the majority lagged some had, as marathag puts it, their act together but funding and changing research requirements meant they fell behind in certain areas. In specific to what I was addressing Blue Steel for example had to have 'valve' driven guidance and control with all that implied for power and support systems. Couple that with the various missteps and blind alleys and overall lack of funding...
As for design I'd note that the British, (unlike almost everyone else) were comfortable and worked well with HTP which due to density and average ISP was comparable with kerolox for such applications. HTP stages tended to be more compact and somewhat lighter mass for the volume due to no cryogenic liquids. They also tended to be more robust by default, (see Black Arrow here: https://en.wikipedia.org/wiki/Black_Arrow, specifically this photo of a 'landed' BA stage; https://en.wikipedia.org/wiki/Black_Arrow#/media/File:Black_Arrow_R3_Stage_1.JPG) which has always made me wonder what recovery would be like.
Had the Gamma motors been replaced with the large chamber Stentor motors and an enlarged tankage system, (see: http://www.spaceuk.org/ba/siddeley.htm) with a Black Knight second stage and to-be-designed HTP third stage would have given the British a "Thor-Delta" class launcher in the early 60s. Adding strap-on solid, (as America did with various versions of the Thor/Delta over the years) would have increased the payload as would have the continued development of hyrdolox upper stages (http://www.spaceuk.org/hydrogen/hydrogen.htm) which had been undertaken by Saunders Roe, (http://www.spaceuk.org/hydrogen/SP510.htm) Roll Royce/Bristol Siddeley, (http://www.spaceuk.org/hydrogen/rr.htm) and of course the RAE, (http://www.spaceuk.org/hydrogen/TechNoteSpace30.htm, http://www.spaceuk.org/hydrogen/TN30.htm) which all proposed and/or studied, (and tested) various engines.
The British were aware of and had early interest in hydrolox engines: http://www.spaceuk.org/hydrogen/hggr.htm
Or course in OTL Black Arrow wouldn't be ready until the late 60s and work on hydrolox ground to a halt with the end of ELDO and by 1962 the US Centaur stage was 'available' for use. But consider for a moment that the British actually had a 'leap' of about two years (@1954 for UK and @1956 for the US though the IDEA has been there prior to in the general community) in interest and study for hydrolox propulsion.
Phx1138 wrote:
uh. So all this time, my focus on high Isp was (at least in part) in error.
It depends on the application actually. For example JP was concerned with high-ISP through the majority of the flight trajectory mostly because he was focused on Single Stage To Orbit and going with the 'conventional-wisdom' of the time therefore assumed hydrolox propellant.
Quite obviously hydrolox gives the highest practical ISP, (note that as there have been studies and designs which used everything from fluorine to "high-density-particulate-materials" as additives to boost that ISP with little regard to actual practicality or utility) of 'standard' chemical propulsion so it is favored but it has enough drawbacks as well, (density, deep-cryogenic temps, etc) that alternatives and 'cheats' cropped up early on.
Duel-fuel, (burning something 'dense' and lower ISP to start and switching to pure LH2 later on) 1.5-STO and 'booster' or "zero-stage" designs have all been suggested but the core of 'purest' SSTO-advocates, (much like the purest Scramjet advocates) consider anything LESS than a 'pure' SSTO as a waste of time and effort. This tends to reflect in any efforts to study any propellant combination with LESS ISP than hydrolox which despite the 'math' working out, (despite studies showing that SSTO is possible with kerolox, keroxide, and methalox the number of studies that specify and defend hydrolox as the only acceptable propellant combo pretty much bury the alternatives) is not given much credence in general discussion.
(This despite two of the main 'examples' of the possibility of SSTO vehicles, the Titan-II first stage, and Atlas, did not in fact use hydrolox propellant)
As fasquadron noted chasing ISP can, and has been, a "Red Queen's Race" beyond a certain point. There was literally a point where all the 'experts' were touting all the fantastic advantages that would be available as soon as "we have hydrogen engines" without addressing, (or even acknowledging) the numerous issues. It has become quite obvious that LH2 as a booster propellant is lacking in efficiency and as it requires a 'boost' to get moving, (there's a reason the Delta-IV/IV Heavy takes a while to get off the pad without solid boosters AND a reason the Delta-IV was to be replaced by the Atlas V and now the Vulcan) otherwise it wastes propellant.
Fasquadron wrote:
Not really the former as oil stocks are stable and there are known sources we've not tapped yet even assuming we don't start 'making' oil from other sources. (Turning coal into 'oil' is still only marginally cost effective but has the distinct advantage of removing almost all the Sulphur and other 'pollutants' in it making it almost as clean a natural gas) The current abundance of natural gas, (which is mostly methane) seems to be what is the main spur to current use of liquid methane though possible 'off-planet' sourcing is often cited. Truth is making methane off-planet is by far one of the least efficient propellants to make ranking only a bit below simpler to make, (but more difficult to store, but not THAT difficult) liquid hydrogen. The other main driver is that the design differences between a methalox and hydrolox engine are very few and the possibility of using existing designs of the latter to build the former are high. (In fact we know that the RL10 can run on methalox with modification and the J2 was studied to do so)
Fscott wrote:
All the above on this one
Thrust oscillation and differences due to grain, mixture and curing is a big problem especially as the overall size gets larger. Overall ISP of a solid is usually lower than that of a liquid though for their usual use, (high thrust, short duration, usually a booster) this isn't as much of an issue but once you get into second, third or even fourth stages their utility diminishes greatly. (As a final or insertion stage they have some advantages but if you have a choice liquids are still better)For example the four stage Scout (https://en.wikipedia.org/wiki/Scout_(rocket_family) could by the end put up a 210kg/463lb payload, the basic Thor-Able/Ablestar could do half that in two stages and Thor-Agena, Thrust Augmented Thor, and Thor-Delta well over twice that. Solids were initially seen as more cost effective than liquids but as size grew so did cost in a non-linear/non-intuitive manner. Once you move beyond strictly military requirements of long-term storability and quick response solids are far less useful outside the realm of booster applications. About the only way they become significantly 'cost-effective' is if the user gets them at a high discount or surplus. Athena, Minotaur/Taurus, Vega, and Conestoga for examples all relied on government surplus "missile" motors or subsides to show competitive costs. Pegasus costs by all estimations should have been much lower than they were but part of the reason this wasn't true was that the solid motors were all specially designed and constructed for the vehicle. Adding a surplus Peacekeeper stage and later adapting surplus Minuteman II stages was a method of increasing payload and lowering costs but once the supply was gone...
Getting off-topic but specifically in the case of Pegasus an independent design suggestion known as Pogo or JELAC, (Jet Engine Launch Assist Concept) replaced the sub-sonic carrier aircraft with a 'booster' using 4 F100 jet engines that took off vertically, staged around Mach-3/4 and about 80Kft then returned to a vertical landing to be reused. Due to the mass reduction, (no wings or tail surfaces to carry or joining structure) payload of a 'basic' Pegasus rose to the level of the later Pegasus XL. A Pegasus XL version put more payload on-orbit than it was designed to handle. Adding a ramjet, (not Scramjet) second stage to around Mach-5/6 doubled the payload. It's hard to find information to link to these days since Glenn Olson's alt.accel.com shut down (about 2010-ish IIRC) but NASA Dryden patented and advertised a 'similar' (with no noting of 'prior art') concept called "Ram-Booster" which used F100s and a ramjet second stage with a Centaur based third stage. "Prior art" would include a study done by Dani Eder of Boing in the mid-70s which didn't use a ramjet but used ten F100s in individual recoverable pods to boost a hydrolox RL10 powered TSTO into orbit with a 6Klb payload to LEO.
Like I said a bit off-topic but if we can assume better economics and some 'sense' in the right places I think British post-WWII aviation and rocketry could have been very different.
Bolt451 wrote:
Black Arrow though it didn't fly till 28 October, 1971 by which time 'better' launchers were available. Blue Streak was the basis of the ELDO launch vehicle and Blue Streak pretty much worked every flight but the entire launcher (Europa) was too small to be of continued interest even the 'augmented' version proposed: http://www.spaceuk.org/bstreak/eldo/augmented.html
Interestingly enough the estimated payload of the LRB version was twice that of the SRB version
The proposed all-British Black Prince LV, (http://www.spaceuk.org/bstreak/bs/bsslv.htm) would have been about equal to Atlas Agena in basic capability. Adding a higher ISP second and third stage would have given something comparable to Atlas Centaur but...
(Hawker Siddeley made a pitch in 1972 to mate the Blue Streak with a Centaur upper stage, payloads to GTO ranged from 650kg up to 1050kg with four SRBs. See: http://www.spaceuk.org/bstreak/bs/bs_centaur.html)
Two alternate Black Arrow designs were put forward, (http://www.spaceuk.org/ba/siddeley.htm) using the bigger Stentor chambers from the Blue Steel instead of the Gamma's and a Black Knight based HTP upper stage. Payload to LEO was somewhere around 650+lbs. Strap-on boosters and a different propellant (higher ISP) for the upper stage is possible. In 1971 an upgraded Black Arrow called SLAVE, (Satellite LAunch VEhicle, really? Can't just go for "SLV" and avoid the issues?) was proposed but obviously not pursued.
Strangely enough a propellant combination that cropped up during RL10 testing, (I swear that engine has probably been run on alcohol or maybe just the test engineers were
) but Propane, cryo-cooled to around LOX storage temps, densifies to around that of kerosene, (aka will fit into the same space/tanks if you add some external insulation) and cryo-propane/LOX gives performance close to that of methalox. (@110% that of kerolox/@80% that of hydrolox)Now have someone make note of the fact that HTP does not in fact decompose spontaneously when cooled to around 41F/5C, (note that's AC cool instead of cryogenic cool like LOX requires) which the US stumbled upon in the late 70s and you get some interesting possible paths.
Randy[/quote]