But having booster and upper stage made of different materials eliminates any production synergism. it would require separate tank production lines.
Quote from: Herb Schaltegger on 08/24/2016 10:33 pmThis isn't a Cold War project like the B-70 (which was ultimately too expensive to produce more than the 3 airframes anyway).Only two XB-70s were built (the second crashed, the first is in the USAF museum in Dayton, OH), and they were almost entirely made of stainless steel, with titanium just in the most critical parts.The SR-71, on the other hand...
This isn't a Cold War project like the B-70 (which was ultimately too expensive to produce more than the 3 airframes anyway).
Quote from: Robotbeat on 08/26/2016 07:37 pmMight make sense to make /portions/ of Falcon out of Titanium. Like the grid fins or maybe parts of the thrust structure. To enhance durability and reduce the amount of TPS you need.But I don't think they'll make the tanks (etc) out of it. Hard to work, not generally as good structure/mass (the lower density of aluminum helps for compressive structures in ways beyond pure strength/weight ratio because of reduced buckling).Called it.
Might make sense to make /portions/ of Falcon out of Titanium. Like the grid fins or maybe parts of the thrust structure. To enhance durability and reduce the amount of TPS you need.But I don't think they'll make the tanks (etc) out of it. Hard to work, not generally as good structure/mass (the lower density of aluminum helps for compressive structures in ways beyond pure strength/weight ratio because of reduced buckling).
Titanium grid fins for supersonic rocket manufacturedQuote from: LIN Industrial3D printed plastic grid fins we currently use can't withstand the dynamic pressure and heating at supersonic. That's why we have started manufacturing titanium grid fins. They are cut from a single piece of titanium with a CNC machine:
3D printed plastic grid fins we currently use can't withstand the dynamic pressure and heating at supersonic. That's why we have started manufacturing titanium grid fins. They are cut from a single piece of titanium with a CNC machine:
Quote from: sevenperforce on 08/25/2016 07:37 pmWell, the MCT is (purportedly) more than just a second stage, so comparing BFR to MCT is less like comparing Falcon 9's stage 1 to stage 2 and more like comparing Falcon 9's stage 1 to the Dragon 2.No, it is still the same comparison. The MCT will have a propulsion system with elements common to the booster.
Well, the MCT is (purportedly) more than just a second stage, so comparing BFR to MCT is less like comparing Falcon 9's stage 1 to stage 2 and more like comparing Falcon 9's stage 1 to the Dragon 2.
Quote from: Robotbeat on 08/18/2017 04:09 amQuote from: Robotbeat on 08/26/2016 07:37 pmMight make sense to make /portions/ of Falcon out of Titanium. Like the grid fins or maybe parts of the thrust structure. To enhance durability and reduce the amount of TPS you need.But I don't think they'll make the tanks (etc) out of it. Hard to work, not generally as good structure/mass (the lower density of aluminum helps for compressive structures in ways beyond pure strength/weight ratio because of reduced buckling).Called it.For historical interest only, mvpel may have called it first. The idea was certainly rattling around:Quote from: mvpel on 06/02/2016 12:19 amTitanium grid fins for supersonic rocket manufacturedQuote from: LIN Industrial3D printed plastic grid fins we currently use can't withstand the dynamic pressure and heating at supersonic. That's why we have started manufacturing titanium grid fins. They are cut from a single piece of titanium with a CNC machine:
shout out to dorkmo for starting that clairvoyant thread
On a slightly more factual note, I was always impressed that the Soviet Union managed to build whole large submarine pressure hulls out of the stuff. None of which is germane to Falcon 9, of course!
Actually they are XB-70A's the original XB-70 programme ended when the B-70 programme was cancelled. XB-70A research programme replaced the XB-70 development programme: http://www.boeing.com/history/products/xb-70-valkyrie.page
Yeah, it's definitely possible to get lower than 4% weight for legs. This is a point HMXHMX often makes.
Quote from: Robotbeat on 08/24/2017 12:27 pmYeah, it's definitely possible to get lower than 4% weight for legs. This is a point HMXHMX often makes.True but that misses the point. It's basically a time honored heuristic of aircraft design. But AFAIK there is no equivalent heuristic for VTOL, although I think Armadillo and Masten have both done enough to have some number in mind depending on wheather you want it to stand on them fully fueled or only deploy when the tanks are nearly empty. That's clearly going to make a big difference to what mass you need to assign given loads. IDK, for a fully fueled VTO stage 4% might be too low, while for gear that's only going to be needed during it's near empty landing it's grossly high, but by how much? "Vertical Landing" (as a thing) is not going to go away any time soon.
Quote from: john smith 19 on 08/24/2017 04:11 pmQuote from: Robotbeat on 08/24/2017 12:27 pmYeah, it's definitely possible to get lower than 4% weight for legs. This is a point HMXHMX often makes.True but that misses the point. It's basically a time honored heuristic of aircraft design. But AFAIK there is no equivalent heuristic for VTOL, although I think Armadillo and Masten have both done enough to have some number in mind depending on wheather you want it to stand on them fully fueled or only deploy when the tanks are nearly empty. That's clearly going to make a big difference to what mass you need to assign given loads. IDK, for a fully fueled VTO stage 4% might be too low, while for gear that's only going to be needed during it's near empty landing it's grossly high, but by how much? "Vertical Landing" (as a thing) is not going to go away any time soon.The F9 is about 27 tonnes (or tons?) at landing according Hans K. The legs are about as much as a Model S (about 2,000 kg) according to Elon. So that's between 7.4% and 8.1% of the landing mass, depending on whether Hans meant short or metric tons.Either way, a lot more than 4%...
Well that's intriguing. Definitely not my instinct would have been. So 7-8+% of gross landing weight. I'm pretty sure one of the (theoretical) benefits of VL was expected to be it's very low landing gear penalty compared to the wheeled landing gear on HTOL or VTOHL systems.This suggests that has not really worked out IRL. Perhaps the new on deck grabber robot will help?