Quote from: momerathe on 12/25/2016 03:17 pmQuote from: Katana on 12/25/2016 09:36 amThe only benefit of SABRE over ramjet is start from zero speed to supersonic , which could also be done by conventional rocket engine, no heavier than the SABRE core and cost ~20% of total propellant. I'm pretty sure the bolded statement is wrong. A conventional rocket has lower effective ISP, and therefore must use more fuel, almost by definition.You're misinterpreting what Katana is saying. When Katana says "cost ~20% of total propellant" that means cost in addition to the prop that would be there for SABRE. That's because Katana is agreeing with you that Isp is higher for SABRE so 20% more prop is needed for the non-SABRE alternative.
Quote from: Katana on 12/25/2016 09:36 amThe only benefit of SABRE over ramjet is start from zero speed to supersonic , which could also be done by conventional rocket engine, no heavier than the SABRE core and cost ~20% of total propellant. I'm pretty sure the bolded statement is wrong. A conventional rocket has lower effective ISP, and therefore must use more fuel, almost by definition.
The only benefit of SABRE over ramjet is start from zero speed to supersonic , which could also be done by conventional rocket engine, no heavier than the SABRE core and cost ~20% of total propellant.
Quote from: john smith 19 on 12/24/2016 06:49 pmQuote from: Katana on 12/24/2016 05:45 pmSABRE runs very close to ramjet at M5.Heat absorbing capability of LH2 is about 1/10 of combustion energy release. While at M5 the energy of air is near to combustion energy release. So the amount of cooled air is much lesser than hydrogen used in cooling, most part of hydrogen are burned in bypass channel.I'm not clear what point you're trying to make. Could you be a little clearer?At high Mach number the SABRE core could only cool and compress tiny amounts of extremely hot air. The operation cycle and hence the thrust performance converges to standard ramjet, and the core becomes dead weight.The only benefit of SABRE over ramjet is start from zero speed to supersonic , which could also be done by conventional rocket engine, no heavier than the SABRE core and cost ~20% of total propellant. The structure weight and fuel consumption of standard ramjet+rocket is not much worse than SABRE, but much easier to build.
Quote from: Katana on 12/24/2016 05:45 pmSABRE runs very close to ramjet at M5.Heat absorbing capability of LH2 is about 1/10 of combustion energy release. While at M5 the energy of air is near to combustion energy release. So the amount of cooled air is much lesser than hydrogen used in cooling, most part of hydrogen are burned in bypass channel.I'm not clear what point you're trying to make. Could you be a little clearer?
SABRE runs very close to ramjet at M5.Heat absorbing capability of LH2 is about 1/10 of combustion energy release. While at M5 the energy of air is near to combustion energy release. So the amount of cooled air is much lesser than hydrogen used in cooling, most part of hydrogen are burned in bypass channel.
It's not obvious what the advantages of such a platform would be over a satellite, but hey, at least the military vapourware peddlers haven't forgotten us .
Also, before watching that video I had no idea atmospheric lensing was a thing. Most references describe it as a problem for laser transmission, rather than a exploitable phenomenon though.
It does demonstrate that BAE have brought their way into REL purely for the defence applications of the technology. I am increasingly convinced that at this time they have little to no interest in its civilian applications.
Quote from: Star One on 01/16/2017 05:49 pmIt does demonstrate that BAE have brought their way into REL purely for the defence applications of the technology. I am increasingly convinced that at this time they have little to no interest in its civilian applications.I think that's a fairly common opinion. They know which side their bread is buttered, after all. However, if that funds SABRE to the point where there is a working, flying engine then I think hope that will open the way to civilian applications.
It's not obvious what the advantages of such a platform would be over a satellite, but hey, at least the military vapourware peddlers haven't forgotten us .Also, before watching that video I had no idea atmospheric lensing was a thing. Most references describe it as a problem for laser transmission, rather than a exploitable phenomenon though.
Quote from: Star One on 01/16/2017 05:49 pmIt does demonstrate that BAE have brought their way into REL purely for the defence applications of the technology. I am increasingly convinced that at this time they have little to no interest in its civilian applications.It's a PR video. But we know BAE has no civilian interests. It's all defense or government related. No general customers like a normal business.
The Development and Potential of the Skylon Spaceplane and its Sabre Engines22 February 2017Derby BranchLectureMark Thomas, Chief Executive Officer, Reaction Engines Ltd will give a lecture to the RAeS Derby branch.
I noticed there is a 'thing' going on with Mark Thomashttps://www.aerosociety.com/events-calendar/the-development-and-potential-of-the-skylon-spaceplane-and-its-sabre-engines/QuoteThe Development and Potential of the Skylon Spaceplane and its Sabre Engines22 February 2017Derby BranchLectureMark Thomas, Chief Executive Officer, Reaction Engines Ltd will give a lecture to the RAeS Derby branch.