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RD-180 relplacement
I'm confused. The program to replace the RD-180 is focused on engines
with around 400,000 lb thrust at sea level. This focuses them on the AR-1 (kerosene/LOC) and BE-4 (methane/LOX). Why are they not looking at the RS-25 (LH2/LOX with similar thrust) or the Raptor engine (methane/LOX)? Seems like we're getting a lot of different engines when it might be more efficient to settle on just a couple. -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw |
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RD-180 relplacement
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#3
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RD-180 relplacement
Jeff Findley wrote:
In article , says... I'm confused. The program to replace the RD-180 is focused on engines with around 400,000 lb thrust at sea level. This focuses them on the AR-1 (kerosene/LOC) and BE-4 (methane/LOX). Why are they not looking at the RS-25 (LH2/LOX with similar thrust) or the Raptor engine (methane/LOX)? RS-25 is hella expensive and ULA already knows that LH2/LOX produces a large, expensive, vehicle (e.g. Delta IV). So that's right out since Delta IV is already flying (no development costs there). But do note that ULA really wants to ax Delta IV in favor of Atlas V due to its high cost. So why aren't they using something other than RS-25 on SLS? Raptor (methane/LOX) isn't "fully baked" yet (BE-4 is ahead of it). That sounds wrong to me. SpaceX test fired a full up Raptor engine (albeit a lower thrust developmental engine) at their Texas facility last year. The BE-4 has never been test fired and they didn't even have a full engine put together until this year. Seems like we're getting a lot of different engines when it might be more efficient to settle on just a couple. AR-1 is a "backup" engine at this point since it's so far behind BE-4 in both schedule and (estimated) per unit price. But, AR-1 is about the right size for two of them to be a "drop-in" replacement for RD-180 on Atlas V. So, if ULA stumbles on Vulcan, an AR-1 engined Atlas V might be a good stop-gap measure. Aerojet Rocketdyne says they can start delivering AR1 engines in 2019, so the finish line isn't all that far behind BE-4. Blue Origin says the BE-4 will cost 60% of what an AR1 costs (at $12.5 million each); so BE-4 engines are only around $7.5 million each? The government is paying a lot of money to develop AR1, so I'd bet on it being pushed for use somewhere. And AR1 does have the advantage of not needing a bunch of new infrastructure to handle fueling and such. At any rate, Aerojet Rocketdyne is being paid good money to develop AR- 1. Even if it meets the same fate as J-2X, they're getting money now which helps keep the company alive. How many billion dollars of taxpayer money are we going to spend developing engines that never get used? Around $1.5 billion for AR1. Around $1.2 billion for RS-25 (which only gets used if SLS keeps flying). Another $1.2 billion for J-2X. Meanwhile Merlin engines used on Falcon 9 cost around $1.2 million each with engines in the Raptor/BE-4 class going for $7.5 million each? Meanwhile the entire development budget for New Glenn is around $2.5 billion and what little public data there is puts development costs for Raptor engines in the hundreds of millions of dollars (vice billions) and I expect BE-4 development is similar. What that says is that private companies developing engines mostly on their own nickel is looking to be an order of magnitude cheaper than traditional contracted engine development programs... -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw |
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RD-180 relplacement
JF Mezei wrote:
On 2017-05-09 22:28, Jeff Findley wrote: RS-25 is hella expensive and ULA already knows that LH2/LOX produces a large, expensive, vehicle (e.g. Delta IV). With the R&D money given to Rocketdyne to enable production of more SSMEs, has it given any hints that the incremental unit cost would come down significantly with modern tooling compared to the orgiginal SSME production ? The first six will cost about what the original SSME engines cost (around $58 million each in current dollars). (aka: once beyond the first 6, would additional ones become competitive on a per pound of payload basis ? (engine only). One would expect subsequent RS-25 engines to cost less as the 'kinks' are worked out of the production and test processes. However, these engines will always be more expensive than engines like BE-4 or Raptor (or even AR1), so they're never going to compete on a price per pound basis. -- "Millions for defense, but not one cent for tribute." -- Charles Pinckney |
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RD-180 relplacement
JF Mezei wrote:
On 2017-05-10 05:30, Fred J. McCall wrote: So why aren't they using something other than RS-25 on SLS? Because NASA got 16 SSMEs for free when they retired the shuttle. Not a reasonable reason to bet the long term farm on that engine. With regards to production costs, considering new tooling is being built with 21st century tech to produce new SSMes, shoudln't production costs go way down? Not nearly as much as you think. The expense of producing the engine is largely because of the engine. Back in the 1970s, "state of the art" aircraft engines were roughly 45,000lbs of thrust. Today, modern CAD/CAM makes ~115,000lbs aircraft engines commercially viable and in fact, the 777 has won huge market share with those engines compared to older generation qhich required quad engines on planes. Uh, what does that have to do with anything? Yes, we could build bigger and cheaper rocket engines than the RS-25 (and both SpaceX and Blue Origin are doing so). But those engines aren't RS-25s. Isn't it likely that while producing SSMEs in the 1970s was way beyond commercial "state of the art" and thus very expensive, modern CAD/CAM would be well capable of automating production of parts with the required tolerances for those engines? No. RS-25 is a high performance engine (still). Or put another way: are SSMEs still beyond what modern tooling can build? Or is it more a question of Rocketdyne just taking money from NASA and not caring about making this a viable product ? Engines like RS-25 are still going to require a lot of 'touch labor'. -- "Millions for defense, but not one cent for tribute." -- Charles Pinckney |
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RD-180 relplacement
On Wednesday, May 10, 2017 at 5:30:17 AM UTC-4, Fred J. McCall wrote:
Jeff Findley wrote: In article , says... I'm confused. The program to replace the RD-180 is focused on engines with around 400,000 lb thrust at sea level. This focuses them on the AR-1 (kerosene/LOC) and BE-4 (methane/LOX). Why are they not looking at the RS-25 (LH2/LOX with similar thrust) or the Raptor engine (methane/LOX)? RS-25 is hella expensive and ULA already knows that LH2/LOX produces a large, expensive, vehicle (e.g. Delta IV). So that's right out since Delta IV is already flying (no development costs there). But do note that ULA really wants to ax Delta IV in favor of Atlas V due to its high cost. So why aren't they using something other than RS-25 on SLS? Raptor (methane/LOX) isn't "fully baked" yet (BE-4 is ahead of it). That sounds wrong to me. SpaceX test fired a full up Raptor engine (albeit a lower thrust developmental engine) at their Texas facility last year. The BE-4 has never been test fired and they didn't even have a full engine put together until this year. Seems like we're getting a lot of different engines when it might be more efficient to settle on just a couple. AR-1 is a "backup" engine at this point since it's so far behind BE-4 in both schedule and (estimated) per unit price. But, AR-1 is about the right size for two of them to be a "drop-in" replacement for RD-180 on Atlas V. So, if ULA stumbles on Vulcan, an AR-1 engined Atlas V might be a good stop-gap measure. Aerojet Rocketdyne says they can start delivering AR1 engines in 2019, so the finish line isn't all that far behind BE-4. Blue Origin says the BE-4 will cost 60% of what an AR1 costs (at $12.5 million each); so BE-4 engines are only around $7.5 million each? The government is paying a lot of money to develop AR1, so I'd bet on it being pushed for use somewhere. And AR1 does have the advantage of not needing a bunch of new infrastructure to handle fueling and such. Three separate heavy lift vehicles in development that would be capable of taking men to the Moon or Mars. I don't really understand that. Last time one vehicle was developed and they built 16 of them and had programs in place to use them within a reasonable period of time, that provided economies of scale and focus to do the program. It was a national scale program and accomplished great things. The current approach doesn't make sense; too many vehicle types in development and no real focus toward building enough of them to have an actual program. |
#7
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RD-180 relplacement
To know the kind of engine you need, you need to know the vehicle it will be used for. To know the kind of vehicle you need, you need to know where it is going and what the vehicle is used for. To know where you are going and what you are doing, you have to have a long-term plan. Is anyone doing this? NASA is not - not officially. China is - officially. * * * Chinese Engines YF-77 (165,000 lbf) http://aviationweek.com/awin/chinese...xceed-saturn-v Chinese Vehicles Long-March 11 (140,000 lb LEO) http://www.americaspace.com/2012/07/...g-new-rockets/ Chinese Missions Mars http://en.people.cn/200705/22/eng20070522_376754.html Solar Power Satellite http://news.xinhuanet.com/english/20..._134109115.htm * * * A 140,000 lb payload to orbit, built with a common core and two outboard stages - all to the same design. Five Y-77 engines on each. So, three modules each the same size and weight is about 1/2 the size of a Space Shuttle External Tank, with FIVE Y-77 engines at the base of each. Each module; 316 tonnes module weight 36 tonnes structure weight Structure 43 tonnes LH2 237 tonnes LOX 77 Y-77 Engine Thrust 5 Number of Engines 1.218 Gees at lift off. So, theres a core, and two outboard tanks, equipped with cross feeding, drain the two outboard tanks first and blast off with 15 Y-77 engines. When the two outboard tanks are drained they are dropped and fly back to the launch centre after boosting the system to 2.2 km/sec. The central core adds another 5.8 km/sec to attain orbit with 63.6 tonnes payload. The central core re-enters, and returns to the launch centre. * * * Reaching for 400,000 lbs. Expanding to 7 common core boosters with five Y-77 engines - raises the weight higher. A seven element launcher puts up 182.0 tonnes payload (400,000 lbs) with four elements dropping off and flying back to the launch centre after adding 1.5 km/sec. The three element system continues as the second stage. The two elements dropping off after taking the vehicle up to 4.3 km/sec. Then finally the core element takes 182 metric tons to LEO. All fly back to be reused. * * * What to do when you get to orbit - Interplanetary Stages - Nuclear thermal stage - One interesting detail is the development of ceramic coated pellets of uranium that contain liquid uranium under supreme heating achieving 1600 sec Isp (15.68 km/sec Ve) using liquid hydrogen. This is an old idea, going back to the 1960s; https://books.google.co.nz/books?id=...XGA9cQ6AEIJTAA A 4000 MW thermal nuclear rocket the size of NERVA, operating at this level, produces 52.0 metric tons of thrust. The advantage of this system 182 metric ton payload can deliver a lot more across the solar system than chemical rockets! https://www.lanl.gov/science/NSS/iss...ory4full.shtml Nuclear Electric Stage The nuclear thermal source is also used as a power supply using a closed Brayton cycle process. This produces 2000 MW electrical, from a 4000 MW thermal source which when used in an advanced ion engine that produces 54 km/sec exhaust speed (5500 sec Isp) produces 7.5 tonnes of thrust providing even greater payload fractions to Mars and beyond, and mass only 1.5 tonnes. On board Nuclear Electric & Nuclear Electric on Mars A nuclear thermal source will be used as a power supply to power the ship, the same way the nuclear power plant on a nuclear sub is used. The nuclear thermal source will be used as a power supply after landing. To power a lunar or mars or other planetary city. Including industrial processes that produce chemical fuels on Mars for boosters. http://emits.sso.esa.int/emits-doc/E...33-SoW-RD1.pdf For all these reasons, anyone serous about deep space manned travel will develop nuclear rocketry. The PR angle The technology is different enough from existing power plant designs, that they can be incorporated in advanced high temperature reactors on Earth, and the high profile nature of the successful missions they enable, are sufficient to promote their high technology, high reliability and high safety. A definite coup. Something the Chinese would exploit mid 21st century to sell compact high efficiency flexible power plants to cities and nations around the world struggling in a post oil future. https://www.gen-4.org/gif/jcms/c_9362/vhtr The radiation angle What about radiation? Well, Cosmic Background Radiation and Solar radiation outside vanAllen belts of Earth, are definite safety hazards as well. The shielding required of a nuclear source could also shield astronauts aboard ship. A shadow shield has long been promoted as a 'safe haven' or 'storm shelter' or even a 'sun shield' for manned interplanetary missions. Another is to use powerful electro magnet and surplus electrical power to make a mini-magnetic shield around the ship. https://home.cern/about/updates/2015...eld-astronauts * * * It takes 3.6 km/sec to exit LEO and head for Mars along a Hohmann Transfer Orbit. So, propellant fractions are; Chemical u = 1 - 1/exp(3.6/4.3) = 0.557 -- 39,930 lbs useful of 140,000 lbs, 114,100 lbs useful of 400,000 lbs Nuclear Thermal u = 1 - 1/exp(3.6/15.68) = 0.200 -- 98,970 lbs useful of 140,000 lbs, 282,770 lbs useful of 400,000 lbs Nuclear Electric u = 1 - 1/exp(3.6/54) = 0.063 -- 118.190 lbs useful of 140,000 lbs, 337,700 lbs useful of 400,000 lbs A nuclear thermal rocket powered stage delivers 2.48x what a chemical stage delivers. A nuclear electric rocket powered stage delivers 2.96x what a chemical stage delivers. Now, a nuclear electric power source has a lot of other uses as well! So, a nuclear electric source, built around a nuclear thermal rocket, is a reasonable add-on to a nuclear thermal rocket programme. If you're going to send large numbers of payloads across the solar system, you can do it more cheaply with the right engines, and nuclear rockets are the right engines. * * * Now this uses 1950s era technologies, updated slightly for today. Something the Chinese would feel comfortable doing as part of an integrated programme. https://www.google.co.nz/url?sa=t&rc...e4ZL10FXWssogw So, despite the small size of the Chinese Space Budget about 1/10th the size of NASA, in combination with support from the Chinese nuclear weapons and power programmes, a credible effort is being sustained along the lines described here. |
#8
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RD-180 relplacement
"Scott M. Kozel" wrote:
On Wednesday, May 10, 2017 at 5:30:17 AM UTC-4, Fred J. McCall wrote: Jeff Findley wrote: In article , says... I'm confused. The program to replace the RD-180 is focused on engines with around 400,000 lb thrust at sea level. This focuses them on the AR-1 (kerosene/LOC) and BE-4 (methane/LOX). Why are they not looking at the RS-25 (LH2/LOX with similar thrust) or the Raptor engine (methane/LOX)? RS-25 is hella expensive and ULA already knows that LH2/LOX produces a large, expensive, vehicle (e.g. Delta IV). So that's right out since Delta IV is already flying (no development costs there). But do note that ULA really wants to ax Delta IV in favor of Atlas V due to its high cost. So why aren't they using something other than RS-25 on SLS? Raptor (methane/LOX) isn't "fully baked" yet (BE-4 is ahead of it). That sounds wrong to me. SpaceX test fired a full up Raptor engine (albeit a lower thrust developmental engine) at their Texas facility last year. The BE-4 has never been test fired and they didn't even have a full engine put together until this year. Seems like we're getting a lot of different engines when it might be more efficient to settle on just a couple. AR-1 is a "backup" engine at this point since it's so far behind BE-4 in both schedule and (estimated) per unit price. But, AR-1 is about the right size for two of them to be a "drop-in" replacement for RD-180 on Atlas V. So, if ULA stumbles on Vulcan, an AR-1 engined Atlas V might be a good stop-gap measure. Aerojet Rocketdyne says they can start delivering AR1 engines in 2019, so the finish line isn't all that far behind BE-4. Blue Origin says the BE-4 will cost 60% of what an AR1 costs (at $12.5 million each); so BE-4 engines are only around $7.5 million each? The government is paying a lot of money to develop AR1, so I'd bet on it being pushed for use somewhere. And AR1 does have the advantage of not needing a bunch of new infrastructure to handle fueling and such. Three separate heavy lift vehicles in development that would be capable of taking men to the Moon or Mars. Actually only one 'program'. And two commercial efforts. I don't really understand that. Last time one vehicle was developed and they built 16 of them and had programs in place to use them within a reasonable period of time, that provided economies of scale and focus to do the program. It was a national scale program and accomplished great things. Last time we had a single government program that spent money like water, made the trip, and then had no follow-on, which is why we can't get beyond LEO anymore. The current approach doesn't make sense; too many vehicle types in development and no real focus toward building enough of them to have an actual program. The 'government program' (how we did Apollo) is the high priced spread. It's true that it makes no sense because it has no real goal (it changes with every President) and is too expensive to fly. The other two efforts are commercial efforts, make more sense, spend a lot less money, and will be far cheaper to fly. If we did it the old way, we would ONLY have SLS, Musk and Bezos would keep their money, and we'd get another 'flags and footprints' mission to somewhere at best. -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw |
#9
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RD-180 relplacement
JF Mezei wrote:
On 2017-05-10 18:35, Fred J. McCall wrote: Uh, what does that have to do with anything? Yes, we could build bigger and cheaper rocket engines than the RS-25 (and both SpaceX and Blue Origin are doing so). But those engines aren't RS-25s. Not what I meant. At the time the SSMEs were built, they pushed the limits of manufacturing and materials process so very expensive to build. True. And they still have a higher power to weight ratio than any other rocket engine, which means they still have to push those things. Part of the redesign is making what changes they can to reduce costs since the engines don't have to refly, but you can only do so much of that before you're no longer talking about an RS-25, but some similar heavier engine. If, like SpaceX does, you apply moden manufacturing techniques, can't the cost go down significantlty through the use of automation to create complex parts with exacting precision? No. Engines like RS-25 are still going to require a lot of 'touch labor'. why? Because. If robots build parts with exacting precision, you don't need a human to use fine sand paper for 2 years to get the thickness just right since the robot will have done that for you in hours. Except it doesn't work like that. You're fooling yourself with that 'exacting precision' phrase. There is always some imprecision in the parts. Without the touch labor on a system that requires very high precision you will throw away a lot of parts. -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
#10
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RD-180 relplacement
William Mook wrote:
To know the kind of engine you need, you need to know the vehicle it will be used for. To know the kind of vehicle you need, you need to know where it is going and what the vehicle is used for. To know where you are going and what you are doing, you have to have a long-term plan. Is anyone doing this? NASA is not - not officially. China is - officially. * * * Chinese Engines YF-77 (165,000 lbf) http://aviationweek.com/awin/chinese...xceed-saturn-v So a smaller engine than RS-25, BE-4, AR-1, or Raptor. About the size of the Merlin engines that SpaceX builds for use on Falcon. Chinese Vehicles Long-March 11 (140,000 lb LEO) http://www.americaspace.com/2012/07/...g-new-rockets/ Uh, what does that citation have to do with Long March 11? It doesn't even mention it and it's largely about paper rockets. Long March 11, meanwhile, is about the size of Falcon Heavy. snip speculative MookSpew -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw |
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