The IAC update seems to have happened but I can't find any crumbs of news or comments about it:https://iafastro.directory/iac/paper/id/31601/summary/
Quote from: t43562 on 10/13/2015 03:10 pmThe IAC update seems to have happened but I can't find any crumbs of news or comments about it:https://iafastro.directory/iac/paper/id/31601/summary/ " The vehicle can recover to any airfield with compatible latitude at least 6 times per day from any orbit, and can recover to an Equatorial airfield from a low inclination orbit (less than 40 degrees) on any pass. It was also found that the vehicle is capable of operating from any airfield, overflying any location on Earth, and recovering to the same airfield within a single orbit."Now I wonder who would find that last part useful?
Quote from: t43562 on 10/13/2015 03:10 pmThe IAC update seems to have happened but I can't find any crumbs of news or comments about it:https://iafastro.directory/iac/paper/id/31601/summary/Here's the paper, a pretty good read I think.
...Also thrust vectoring seems to be mentioned very often in papers that I found on Google about Dual Throat Nozzles. I wonder if they intend to use it?
Quote from: lkm on 10/15/2015 07:29 pmQuote from: t43562 on 10/13/2015 03:10 pmThe IAC update seems to have happened but I can't find any crumbs of news or comments about it:https://iafastro.directory/iac/paper/id/31601/summary/ " The vehicle can recover to any airfield with compatible latitude at least 6 times per day from any orbit, and can recover to an Equatorial airfield from a low inclination orbit (less than 40 degrees) on any pass. It was also found that the vehicle is capable of operating from any airfield, overflying any location on Earth, and recovering to the same airfield within a single orbit."Now I wonder who would find that last part useful?Actually anyone who's serious about servicing an on orbit asset, like a hotel for example, or collecting the results of an on orbit manufacturing plant.
Quote from: t43562 on 10/16/2015 10:58 am...Also thrust vectoring seems to be mentioned very often in papers that I found on Google about Dual Throat Nozzles. I wonder if they intend to use it?Could you say more? Skylon designs have always had gimbaling nozzles as far as I know. What would be different about dual throat nozzles with SABRE 4?
I think it's fascinating that as we find out how frost control works.....it's suddenly irrelevant :-). So much thinking and wondering about what it was and all for nothing.Also thrust vectoring seems to be mentioned very often in papers that I found on Google about Dual Throat Nozzles. I wonder if they intend to use it?
On page 3 of the report it says:**Also, due to the higher pre-cooler exit temperature compared to SABRE 3, the frost control system is no longer required.**?? What exactly does that mean? They're not getting rid of the heat exchangers, so why don't they need the frost control? Below 0 C and ice forms. Why don't they need frost control now? What temperature will the heat exchangers reduce the intake airflow down to in SABRE 4?
I was thinking more along the lines of being able to responsively launch a Skylon with an ISR package in the payload bay and have it overfly any location on Earth from an airfield in CONUS.
My query about the engines is are they throttling by translating the nozzle adjusting throat area, we know it has to translate anyway and this is something I believe has been explored before with this type of nozzle.
Quote from: lkm on 10/16/2015 11:17 pmI was thinking more along the lines of being able to responsively launch a Skylon with an ISR package in the payload bay and have it overfly any location on Earth from an airfield in CONUS. Given the expanded latitude range that would certainly seem to be possible. Note that right now the only payload REL are committed to supplying (not necessarily building) is the Skylon Upper Stage. Any operator, or customer of an operator, would have to supply that hardware themselves. I'd also not that under normal circumstances there is no reason for Skylon to fly "upside down." However an "Earth Observation" mode could be included in the standard flight control software to roll the vehicle 180deg, open its doors and then close and roll it backward.
Quote from: lkm on 10/16/2015 11:17 pmMy query about the engines is are they throttling by translating the nozzle adjusting throat area, we know it has to translate anyway and this is something I believe has been explored before with this type of nozzle.A running theme of REL work has been to push the SoA (or the common state of practice) only where absolutely necessary.I'm not quite clear what you're suggesting. Do you mean some kind of Pintle injector? Making the whole inner chamber some kind of pintle?Conventional practice has the whole engine gimbal but people have done engines where only the thrust chamber(s) move, although this needs high pressure fluid gimbals rated to chamber pressure, not tank pressure. For throttling I'd guess they can either indirectly throttle the pump drive turbines by controlling heat addition through the pre burner or (with a more direct action) have divert valves to divert some of the propellants back to the pump inlets. These techniques have history going back to the RL10 and J2 (and possibly the RZ20 built by Rolls Royce in the late 60's).
Quote from: john smith 19 on 10/15/2015 11:00 pmQuote from: lkm on 10/15/2015 07:29 pmQuote from: t43562 on 10/13/2015 03:10 pmThe IAC update seems to have happened but I can't find any crumbs of news or comments about it:https://iafastro.directory/iac/paper/id/31601/summary/ " The vehicle can recover to any airfield with compatible latitude at least 6 times per day from any orbit, and can recover to an Equatorial airfield from a low inclination orbit (less than 40 degrees) on any pass. It was also found that the vehicle is capable of operating from any airfield, overflying any location on Earth, and recovering to the same airfield within a single orbit."Now I wonder who would find that last part useful?Actually anyone who's serious about servicing an on orbit asset, like a hotel for example, or collecting the results of an on orbit manufacturing plant.That's a different problem, surely: being able to overfly any point on the Earth and land in one orbit is not the same as being able to rendezvous with an orbiting asset in one orbit.
do you expect substantial costs reduction from getting rid of frost control?
I think it's fascinating that as we find out how frost control works.....it's suddenly irrelevant :-). So much thinking and wondering about what it was and all for nothing.
My thinking was these are their latest mission analysis studies conducted since they began their relationship with the AFRL and perhaps this was indicative of the sorts of questions they were asking.
The SABRE 4 ends the airbreathing mode by translating the entire airbreathing nozzle backwards until the airbreathing throat closes, as it does so the area of the airbeathing throat decreases. Other expansion-deflection nozzles designs throttle thrust by varying the throat area through translating the pintle so if the SABRE 4 airbreathing chambers move with the nozzle then the SABRE 4 can throttle thrust in the same manner. So in a sense that is the SoA for ED nozzles.
Quote from: francesco nicoli on 10/17/2015 11:31 pmdo you expect substantial costs reduction from getting rid of frost control?Probably not much. You've sunk the funds getting it to work. The HX's will be a bit simpler but I suspect not much simpler. The bulk of them will still be the LH2 network and that's going to be get much simpler.
Quote from: lkm on 10/17/2015 10:00 amMy thinking was these are their latest mission analysis studies conducted since they began their relationship with the AFRL and perhaps this was indicative of the sorts of questions they were asking.Probably not.The work with ARFL was for SABRE, the engine.These analyses apply to SKylon, the vehicle, which AFAIK had nothing do to with the AFRL contract.However it is interesting they validated their trajectory analysis codes against a NASA system, although It's not clear where they got that from. Quite a lot of NASA stuff is available as source code (like their combustion modelling codes).
Quote from: lkm on 10/17/2015 10:00 am The SABRE 4 ends the airbreathing mode by translating the entire airbreathing nozzle backwards until the airbreathing throat closes, as it does so the area of the airbeathing throat decreases. Other expansion-deflection nozzles designs throttle thrust by varying the throat area through translating the pintle so if the SABRE 4 airbreathing chambers move with the nozzle then the SABRE 4 can throttle thrust in the same manner. So in a sense that is the SoA for ED nozzles.I think you're talking about the inlet end of SABRE. While it's technically a pintle I think most people call it an aerospike. I imagine changing overall air flow is part of the throttling process and that's certainly going to be part of the design for the ground test engine. While REL's work does seem to have a pintle in the core of the test engines it looks like a straight cylinder to me and I suspect they'll want to keep the engine throttling process as simple as possible.
"19. A nozzle arrangement according to claim 1, further comprising an actuator arrangement that is arranged to move the second portion of the nozzle between the two positions. "