Even the proposed new Raptors and switching to metholox on the core with an upper stage would get more to LEO and probably cheaper. Would only take 8 of the sub scale ones. NASA launched Saturn IB with 8.
Hey Chris, I thought this was a discussion about the RS25 new build. Although I do appreciate the realistic perspective being expresses, because as actually working on the government side (AF actually) on STS inertia and other things makes it impossible for programs to switch horse late in the rac unless there is no alternativ.
Quote from: oldAtlas_Eguy on 07/31/2017 03:56 pmHey Chris, I thought this was a discussion about the RS25 new build. Although I do appreciate the realistic perspective being expresses, because as actually working on the government side (AF actually) on STS inertia and other things makes it impossible for programs to switch horse late in the rac unless there is no alternativ.Are you implying that the 30 years of operational experience, and over 40 years including over 1 million seconds of test stand hotfire experience is NOT applicable to an RS25 engine that has had some of its internals that were designed for reusability substituted for parts that are designed for "single use disposability"/lower cost?
I am really starting to become annoyed with AR(Aerojet Rocketdyne)/NASAs decision to drop the RS25-A, RS25-B, RS-25-C, RS25-D, RS25-E ... Thus we are left with only SLSME type RS-25s in the lineup.
Quote from: oldAtlas_Eguy on 07/31/2017 03:56 pmHey Chris, I thought this was a discussion about the RS25 new build. Although I do appreciate the realistic perspective being expresses, because as actually working on the government side (AF actually) on STS inertia and other things makes it impossible for programs to switch horse late in the rac unless there is no alternativ.New build is even better. RS-25D to RS-25E means it's far cheaper, but all with that lovely reliability.
New build is even better. RS-25D to RS-25E means it's far cheaper, but all with that lovely reliability.
There is no such alternative, if it includes RS-68. RS-68 and SRB are not viable, much like air start SSME.
The previous Ares V baseline was a 10 meter core, powered by 5 RS-68 engines from the Delta IV vehicle – flanked by two 5.0 segment Solid Rocket Boosters as to be used on the Ares I’s First Stage. The J-2X powered Upper Stage had already changed from 8.4 meters in diameter to a 10 meter stage, flush with the Core Stage.However, the earlier Ares-V configuration has been suffering from an inability to close the performance requirements for being able to heavy lift the four-man Altair Lunar Lander being planned. With Ares I lifting the Orion spacecraft, the Ares-V needs to push 75.1 mT of payload through Trans-Lunar Injection (TLI) but was only able to push 64.6 mT.This new more powerful configuration, identified as the ‘LV 51.00.48’ is now able to put 71.1 mT through TLI. While this configuration still can not reach its targets, this is a clear improvement towards closing the performance requirements NASA has for the Lunar architecture.Each new reusable 5.5 segment SRB, will contain over 1.5 million pounds of propellant which will produce a peak of 3,774,000 million lbs of thrust and will have a vacuum Isp of 275.5 seconds. The 38 percent larger SRB’s will burn for 116 seconds – a full 8 seconds shorter burn time than Space Shuttle – before being jettisoned.They feature a new ‘333-07 Trace’ PBAN solid propellant mix derived from that currently used by the Shuttle, although there is still the option to go to a new HTPB mix if the trade studies are favorable.To accommodate the new lengthened boosters, the Liquid Hydrogen Tank on the Core Stage has been stretched by 190.3”. Together with a proportional stretch to the Liquid Oxygen Tank this growth puts the new baseline vehicle at 381.1 ft tall – nearly 20 feet taller than the old baseline.To save weight, this version of Ares V assumes all non-pressurized structures on the Core Stage will be built out of new IM7 composite materials instead of more traditional Aluminum-Lithium alloy.The 6 RS-68 engines powering the Core will fly at 108 percent power levels (6 percent higher than used on Delta-IV currently) and will each produce 702,055 lbs of thrust and have an Isp of 365 seconds at sea level and will have 797,000 lb of thrust and will have an Isp of 414 seconds in a vacuum.Total expected burn time for the Core will be 303 seconds and the 6 main engines will produce a maximum of 4.17G during the launch. The EDS will likewise be constructed out of mostly composite materials.The J-2X engine will burn at the 100 percent power level for the orbital insertion burn, but will burn at the 81 percent power level for TLI. The reduced thrust optimizes the Isp for the mass-critical TLI burn. The insertion altitude has been raised from 120 nmi to 131.5 nmi circular.Total roll out weight with the crawler and the MLP (Mobile Launch Platform) will be approximately 18 million lbs, which exceeds the capability of the existing crawlerway rated for 16.8 million lbs. The ability for Ares V to remain within its budget targets is now considered a 4×4 risk on the standard 5×5 risk matrix.
Quote from: Chris Bergin on 07/31/2017 06:05 pmNew build is even better. RS-25D to RS-25E means it's far cheaper, but all with that lovely reliability. To pull 25D out of the shed and build up 25E production capacity costed around $70mil/engine ($1.18bil / 16engines) and the new 25E will also cost about the same ($413mil / 6engines, 4flying) compared to RS-68 at around $20mil/engine and fewer per core compared to 25s.Quote from: Jim on 07/29/2017 03:24 pmThere is no such alternative, if it includes RS-68. RS-68 and SRB are not viable, much like air start SSME. Jim, You're very knowledgeable, but mistaken here. RS-68 and SRB is an engineering challenge, not an impossibility. NASA's conclusion was regen at around $150mil in development and doubling the unit cost. I disagree with messing up an inexpensive, robust and impeccably-reliable engine and instead previously outlined a boattail that puts existing 68s in a more benign environment then they have under Delta IV. I'm sure there's other options, possibly some better, to address this engineering problem. -- Boattail post;https://forum.nasaspaceflight.com/index.php?topic=38069.msg1706197#msg1706197
... Wrote an article in 2008 on it. Article is several CMS's ago so looks messy, best to just copy and paste it:Quote... the Ares-V needs to push 75.1 mT of payload through Trans-Lunar Injection (TLI) but was only able to push 64.6 mT. ... This new more powerful configuration, identified as the ‘LV 51.00.48’ is now able to put 71.1 mT through TLI....Total expected burn time for the Core will be 303 seconds and the 6 main engines will produce a maximum of 4.17G during the launch....Total roll out weight with the crawler and the MLP (Mobile Launch Platform) will be approximately 18 million lbs, which exceeds the capability of the existing crawlerway rated for 16.8 million lbs. ...
... the Ares-V needs to push 75.1 mT of payload through Trans-Lunar Injection (TLI) but was only able to push 64.6 mT. ... This new more powerful configuration, identified as the ‘LV 51.00.48’ is now able to put 71.1 mT through TLI....Total expected burn time for the Core will be 303 seconds and the 6 main engines will produce a maximum of 4.17G during the launch....Total roll out weight with the crawler and the MLP (Mobile Launch Platform) will be approximately 18 million lbs, which exceeds the capability of the existing crawlerway rated for 16.8 million lbs. ...
Still didnt address three main problem. Radiant heating of the nozzles from the SRM plume.
Quote from: Chris Bergin on 08/01/2017 01:02 pm... Wrote an article in 2008 on it. Article is several CMS's ago so looks messy, best to just copy and paste it:Quote... the Ares-V needs to push 75.1 mT of payload through Trans-Lunar Injection (TLI) but was only able to push 64.6 mT. ... This new more powerful configuration, identified as the ‘LV 51.00.48’ is now able to put 71.1 mT through TLI....Total expected burn time for the Core will be 303 seconds and the 6 main engines will produce a maximum of 4.17G during the launch....Total roll out weight with the crawler and the MLP (Mobile Launch Platform) will be approximately 18 million lbs, which exceeds the capability of the existing crawlerway rated for 16.8 million lbs. ...That's extraordinary. Refreshing memory and it's still jaw-dropping how absurd Constellation was.Quote from: Jim on 08/01/2017 01:31 pmStill didnt address three main problem. Radiant heating of the nozzles from the SRM plume. Without bending light, the only possible radiant heating in that boattail design would be through the 68's own exhaust and against their bell's inner walls.
Now, what specific target are we shooting for? SSME is a very complex beast. You just can't wave a wand and magically make it cheaper. What performance levels are required? Uprating? Greater margins for HSF than prior Shuttle ones, because we want to lower our LOC/LOM numbers too?How much are we allowed to change the engine's physical geometry/size (much of the issues were in making a compact, ground start engine for a spaceplane application). How about the feed lines, can we change them too? Can we use electrical instead of hydraulic in certain places? Can we use new materials that will last 1-2 times instead of 30+?Can we eliminate whole portions of the design that might sacrifice 2-15 sec-1 of iSP?Now, we take all of that and run it on the test stand and compare numbers? Can we prove we've met requirements and retained acceptable reliability? Tall order.
Wrong again. The plume is radiant for almost 100 feet. The nozzles will always be in direct view of them. The boat tail design is also non viable
Quote from: Space Ghost 1962 on 07/31/2017 09:04 pmNow, what specific target are we shooting for? SSME is a very complex beast. You just can't wave a wand and magically make it cheaper. What performance levels are required? Uprating? Greater margins for HSF than prior Shuttle ones, because we want to lower our LOC/LOM numbers too?How much are we allowed to change the engine's physical geometry/size (much of the issues were in making a compact, ground start engine for a spaceplane application). How about the feed lines, can we change them too? Can we use electrical instead of hydraulic in certain places? Can we use new materials that will last 1-2 times instead of 30+?Can we eliminate whole portions of the design that might sacrifice 2-15 sec-1 of iSP?Now, we take all of that and run it on the test stand and compare numbers? Can we prove we've met requirements and retained acceptable reliability? Tall order.Indeed. The age old myth of the "small change."So if it's that small (that it does not need full qualification testing) how will it give any significant improvements?If it's so big to need full qualification testing how can you afford it in terms of cost or schedule delay?
Was J2-X worth the time/money over J2-S? If they had kept with J2-S mostly, it might have been used. J2-X likely won't be used.
If an SRB plume is an infinite 180 degrees, it still won't effect the 68's if using a boattail. They're still shielded (other than the absolute lip viewed from directly below, and I mentioned an extra ablative ring here may be necessary, but unlikely), they have constant airflow, no radiant effect on each other, no GG recirculation and purge line rerouted - that's kinda the whole point of building a boattail. If you don't know that, how can understand the design well enough to then call it non viable?