Quote from: FutureSpaceTourist on 03/20/2017 05:44 pm I must admit though that I feel more comfortable with SpaceX's (forced) simpler and more iterative approach.Why?
I must admit though that I feel more comfortable with SpaceX's (forced) simpler and more iterative approach.
Quote from: Underappreciated Engine Components – Bearings[Hydrostatic bearings...]Why do we go to all this trouble instead of just using traditional bearings? Engine life. We’re relentlessly focused on reusability, and properly designed hydrostatic bearings offer the potential for longer engine life without refurbishment. This is one of the many engineering decisions we’ve made that we hope will lead to reusability – not just in principle – but to practical, operational reusability. If “reusability” requires significant refurbishment, inspection, and re-validation between flights, then it simply won’t lead to the far lower launch costs we need to achieve our vision of millions of people living and working in space.
[Hydrostatic bearings...]Why do we go to all this trouble instead of just using traditional bearings? Engine life. We’re relentlessly focused on reusability, and properly designed hydrostatic bearings offer the potential for longer engine life without refurbishment. This is one of the many engineering decisions we’ve made that we hope will lead to reusability – not just in principle – but to practical, operational reusability. If “reusability” requires significant refurbishment, inspection, and re-validation between flights, then it simply won’t lead to the far lower launch costs we need to achieve our vision of millions of people living and working in space.
@spacecom Hydrostatic bearings were one of the innovations that led us to pick the engine. Thrilled to see them working 😌
In what way? We must differentiate between iterations in the design phase and development after the first generation of flight ready engines.I agree that improvements on capability should be a lot easier on BE-4 than on Raptor, just like interations were frequent and significant for Merlin. Raptor seems much harder to improve capabilities.But iterations during design are a totally different thing.
Great post. Nice to see great engineering that Blue are doing.
Quote from: guckyfan on 03/20/2017 06:54 pmIn what way? We must differentiate between iterations in the design phase and development after the first generation of flight ready engines.I agree that improvements on capability should be a lot easier on BE-4 than on Raptor, just like interations were frequent and significant for Merlin. Raptor seems much harder to improve capabilities.But iterations during design are a totally different thing.Sorry if I wasn't very clear, I meant it in the sense you did--improvements after the initial design. A big part of Merlin's success was it's relative simplicity, which allowed SpaceX to manufacture it quickly and incorporate more frequent changes. Similarly, I think BE-4's simpler engine cycle will make design modifications easier in the future in comparison to Raptor's more complicated full-flow staged combustion design.
Quote from: FutureSpaceTourist on 03/20/2017 05:44 pmI must admit though that I feel more comfortable with SpaceX's (forced) simpler and more iterative approach. In a way, the BE-4 is more of a simple, iterative approach than SpaceX's Raptor design. Raptor is a bleeding-edge engine that relies on a lot of new technologies and designs, while the BE-4 is relatively simple, as far as staged-combustion engines go. That should make the BE-4 a lot easier to iterate on than the Raptor.
Quote from: Toast on 03/20/2017 06:49 pmQuote from: FutureSpaceTourist on 03/20/2017 05:44 pmI must admit though that I feel more comfortable with SpaceX's (forced) simpler and more iterative approach. In a way, the BE-4 is more of a simple, iterative approach than SpaceX's Raptor design. Raptor is a bleeding-edge engine that relies on a lot of new technologies and designs, while the BE-4 is relatively simple, as far as staged-combustion engines go. That should make the BE-4 a lot easier to iterate on than the Raptor. do you have proof for your statements as FFSC is not new and has been tested but not flown because of challenges from previous manufacturing techniques and others. First ever FFSC to complete testing was the RD-270 for the cancelled UR-700 and UR-900 programmes. Next was integrated powerhead demonstrator (IPD) by Rocketdyne and last up and in testing is Raptor.
do you have proof for your statements as FFSC is not new and has been tested but not flown because of challenges from previous manufacturing techniques and others. First ever FFSC to complete testing was the RD-270 for the cancelled UR-700 and UR-900 programmes. Next was integrated powerhead demonstrator (IPD) by Rocketdyne and last up and in testing is Raptor.
Quote from: Toast on 03/20/2017 08:31 pmQuote from: guckyfan on 03/20/2017 06:54 pmIn what way? We must differentiate between iterations in the design phase and development after the first generation of flight ready engines.I agree that improvements on capability should be a lot easier on BE-4 than on Raptor, just like interations were frequent and significant for Merlin. Raptor seems much harder to improve capabilities.But iterations during design are a totally different thing.Sorry if I wasn't very clear, I meant it in the sense you did--improvements after the initial design. A big part of Merlin's success was it's relative simplicity, which allowed SpaceX to manufacture it quickly and incorporate more frequent changes. Similarly, I think BE-4's simpler engine cycle will make design modifications easier in the future in comparison to Raptor's more complicated full-flow staged combustion design.I don't think Blue will be modifying BE4 for improved performance. Increased reliability and easier maintenance yes. Both NG and Vulcan (ACES) will have enough performance for most satellites without needing SRBs.
With a constellation of small sats, there is no longer a 'satellite' based performance requirement as the constellation launches are almost 'infinitely' divisible payloads... more like propellant than today's GTO payloads.
do you have proof for your statements as FFSC is not new and has been tested but not flown because of challenges from previous manufacturing techniques and others.
[...] the actual difference: the requirements. SpaceX accepted a lot risks and aggressive requirements because they are not on a clock. And BE-4 tried to curb risk as much as possible to cover their reduced schedule margin.
SpaceX accepted a lot risks and aggressive requirements because they are not on a clock. And BE-4 tried to curb risk as much as possible to cover their reduced schedule margin.
Well, I hope that Raptor will be as important as the V-2 and RD-170 engines. Both had such a legacy that dominated for decades the rocket engine design. Blue is not still ready to make such a breakthough, yet. BE-4, I think, will be their RD-107/Merlin 1 workhorse engine. I expect it to be extremely successful. But for really bleeding edge engine, I expect the next engine, probably to be used on the New Armstrong.
I think that you have to understand the difference between using unproven technologies and an unproven cycle. The FFSC is a bit more complicated, yes. But not as much as people have stated. The power balance is much simpler, you don't have to worry about interseals, and you can scale the cycle up and down in Pc/thrust and/or O/F as you want.Regarding the technologies, both companies are making heavy use of FEM, 3D printing and new hot-oxygen resistant alloys. Blue even has implemented hydrostatic bearing. So, I don't think we know enough regarding the specifics of each to say that Blue has lower technologies risk. It's probable that they have lower rocket cycle risk. But again, there's so little experience with FFSC, that it might just happen to be an "easier" cycle in the long run, albeit initially more expensive.What we know for sure is that Raptor will be a performance curve-breaking design without a schedule pressure, while BE-4 will be a "good enough" design with a very strict schedule. And that is what I think it's the actual difference: the requirements. SpaceX accepted a lot risks and aggressive requirements because they are not on a clock. And BE-4 tried to curb risk as much as possible to cover their reduced schedule margin.