Any chance the new grid fins will pop open on ascent?
Perhaps they can maintain AoA without thrust vectoring, allowing the engine thrust to be used more effectively. For example, the "free" lift generated by the high AoA would be used to gain altitude allowing the engine thrust to more directly contribute to delta v?
Quote from: spacenut on 03/31/2017 02:07 amSo that means 10% more payload for FH to LEO? Then would FH get 60 tons to LEO in reusable mode? What about expendable mode? 70-75 tons? That could mean lots of heavy units for NASA's proposed moon orbiting station, without using the SLS. Several years ago when they were trying to figure out what to do after Shuttle, a lot of guys on this thread said 50 ton units to orbit would be optimal and cheaper with expendable rockets. They were advocating Atlas V heavy, or Atlas V phase II, and Delta IV heavy with solids and cross feed to get to 50 tons. Now SpaceX will soon do it with reusable boosters instead of expendable. Nope that's not how it works. Extra thrust by itself only reduces gravity losses. For FH this helps a little more, cause the center booster can now throttle down sooner and save more fuel for after side booster separation. But that's not 10% more payload to LEO.But the bottom line is only missions to the Moon/Mars and beyond actually need extra performance.A risky enhancement would be to shutdown the 3 center booster engines equipped with restart capability, as the center booster could even shutdown all of its engine at some point if it had the ability to restart them right before side booster sep. Or equip even more center booster engine with restart capability and shut them down too. That would provide much of the cross feed benefits.Perhaps, maybe, who knows, SX could do this for Red Dragon missions, as this would be solely SpaceX's risk.Or after SX demonstrates thousands of M1D engines performing flawlessly.In order to get more benefit from extra thrust, stages would have to be stretched, but the stages are already at the road transportability limit.
So that means 10% more payload for FH to LEO? Then would FH get 60 tons to LEO in reusable mode? What about expendable mode? 70-75 tons? That could mean lots of heavy units for NASA's proposed moon orbiting station, without using the SLS. Several years ago when they were trying to figure out what to do after Shuttle, a lot of guys on this thread said 50 ton units to orbit would be optimal and cheaper with expendable rockets. They were advocating Atlas V heavy, or Atlas V phase II, and Delta IV heavy with solids and cross feed to get to 50 tons. Now SpaceX will soon do it with reusable boosters instead of expendable.
Any chance the new grid fins will pop open on ascent? Perhaps they can maintain AoA without thrust vectoring, allowing the engine thrust to be used more effectively. For example, the "free" lift generated by the high AoA would be used to gain altitude allowing the engine thrust to more directly contribute to delta v?Such a scheme would have to trade off against the extra drag generated by the deployed grid fins. I've no idea if it's worth it. But something like this would match more directly with Elon's statements about increased payload, which don't seem to have the qualifications you'd expect if he were talking about only "increased payload for RTLS launches".
A. long rockets don't fly at a AOA. They try to avoid it.
I have a question on the new grid fins. They will have significant more control authority. I have translated that in my mind as they are bigger. Was I wrong? Will they be bigger or only a different more efficient form?
... Block 5 is more like version 2.5 of Falcon 9, is probably the most accurate way to think about it. And the most important part of block 5 will be operating the engines at their full thrust capability, which is about 7 or 8, almost 10% more than what what they currently run at. Number of other improvements to have reusability - goes to the forged titanium grid fins, so that'll bring in a number of factors - block 5, version 2.5 will also incorporate a number of elements that are important to NASA for human spaceflight.
Elon Musk (answering Chris G's question at the post- SES 10 launch presser):Quote... Block 5 is more like version 2.5 of Falcon 9, is probably the most accurate way to think about it. And the most important part of block 5 will be operating the engines at their full thrust capability, which is about 7 or 8, almost 10% more than what what they currently run at. Number of other improvements to have reusability - goes to the forged titanium grid fins, so that'll bring in a number of factors - block 5, version 2.5 will also incorporate a number of elements that are important to NASA for human spaceflight. (emphasis mine)I've been trying to find more information on what these changes are. My limited NSF search skills brought me to some discussion of the merlins' stress cracking, and NASA wants those addressed before they start launching people. Are there any other (non-paperworky) major modifications required on NASA's behalf? And regarding the engine cracking, has anybody here heard anything about whether or not the redesigned version has reached the test firing stage, etc? And what are the odds that the changes made to solve the stress cracking also permitted that extra performance boost he mentions?
I think Musk's versioning system is designed very specifically to troll detractors...I mean, there's literally exactly one instance of each new numbering scheme
Quote from: Tuts36 on 04/05/2017 03:45 pmElon Musk (answering Chris G's question at the post- SES 10 launch presser):Quote... Block 5 is more like version 2.5 of Falcon 9, is probably the most accurate way to think about it. And the most important part of block 5 will be operating the engines at their full thrust capability, which is about 7 or 8, almost 10% more than what what they currently run at. Number of other improvements to have reusability - goes to the forged titanium grid fins, so that'll bring in a number of factors - block 5, version 2.5 will also incorporate a number of elements that are important to NASA for human spaceflight. (emphasis mine)I've been trying to find more information on what these changes are. My limited NSF search skills brought me to some discussion of the merlins' stress cracking, and NASA wants those addressed before they start launching people. Are there any other (non-paperworky) major modifications required on NASA's behalf? And regarding the engine cracking, has anybody here heard anything about whether or not the redesigned version has reached the test firing stage, etc? And what are the odds that the changes made to solve the stress cracking also permitted that extra performance boost he mentions?I think Musk's versioning system is designed very specifically to troll detractors...I mean, there's literally exactly one instance of each new numbering scheme
Quote from: guckyfan on 04/05/2017 02:58 pmI have a question on the new grid fins. They will have significant more control authority. I have translated that in my mind as they are bigger. Was I wrong? Will they be bigger or only a different more efficient form?IMO larger, and curved, since you can do that easily while forging, and it adds strength.
Quote from: meekGee on 04/05/2017 03:03 pmQuote from: guckyfan on 04/05/2017 02:58 pmI have a question on the new grid fins. They will have significant more control authority. I have translated that in my mind as they are bigger. Was I wrong? Will they be bigger or only a different more efficient form?IMO larger, and curved, since you can do that easily while forging, and it adds strength.There must be a reason for the oblong pentagon shape of the grid fins shown in the ITS video. Maybe they will look more like those. Matthew
IMHO titanium grid fins are big deal if they allow more shallow angle of attack during descent.I've drawn the picture for myself to think about reentry. Shallower path makes the stage to fly longer path @ each atmospheric density, thus arriving to next density with reduced speed. The difference to stresses should be dramatic, as the drag is proportional to v^3.
Quote from: hrissan on 04/06/2017 07:31 amIMHO titanium grid fins are big deal if they allow more shallow angle of attack during descent.I've drawn the picture for myself to think about reentry. Shallower path makes the stage to fly longer path @ each atmospheric density, thus arriving to next density with reduced speed. The difference to stresses should be dramatic, as the drag is proportional to v^3.Drag is proportional to velocity squared, not cubed.