LostCosmonaut Posted September 18, 2018 Report Share Posted September 18, 2018 A thread to discuss all BFR related topics, as it continues in development. Quick summary as of September 2018; Raptor engine in testing Manufacture of rocket has begun Initial suborbital tests planned for 2019 Japanese dude / art project planned for free return trajectory around moon in ~2023 Quote Link to comment Share on other sites More sharing options...
LostCosmonaut Posted September 18, 2018 Author Report Share Posted September 18, 2018 Raptor details: Methane / Liquid Oxygen 380 (!) seconds Specific Impulse 300 atmosphere chamber pressure For comparison to the RD-192, a proposed Russian methalox engine from the 90s; 356 isp 257 atm chamber pressure Sturgeon 1 Quote Link to comment Share on other sites More sharing options...
Sturgeon Posted September 19, 2018 Report Share Posted September 19, 2018 12 hours ago, LostCosmonaut said: Initial suborbital tests planned for 2019 Quote Link to comment Share on other sites More sharing options...
Ramlaen Posted September 19, 2018 Report Share Posted September 19, 2018 Is there a concensus of what the 'flaps' around the BFS's 7 Raptors are? Quote Link to comment Share on other sites More sharing options...
Sturgeon Posted September 19, 2018 Report Share Posted September 19, 2018 4 minutes ago, Ramlaen said: Is there a concensus of what the 'flaps' around the BFS's 7 Raptors are? Cargo modules, Elon said. Quote Link to comment Share on other sites More sharing options...
Ramlaen Posted September 19, 2018 Report Share Posted September 19, 2018 2 minutes ago, Sturgeon said: Cargo modules, Elon said. wut?!? Quote Link to comment Share on other sites More sharing options...
Sturgeon Posted September 19, 2018 Report Share Posted September 19, 2018 1 minute ago, Ramlaen said: wut?!? That's what he said! Quote Link to comment Share on other sites More sharing options...
Collimatrix Posted September 19, 2018 Report Share Posted September 19, 2018 2 hours ago, Ramlaen said: wut?!? Yeah, modular cargo modules that can be removed in order to accommodate bulkier vacuum-optimized nozzles if I remember the surreal press conference correctly. Quote Link to comment Share on other sites More sharing options...
LostCosmonaut Posted September 19, 2018 Author Report Share Posted September 19, 2018 The Raptor getting 380 seconds specific impulse is a pretty big deal. However, I'd say it's an even bigger deal that it's running at 300 bar (30 MPa real units) chamber pressure. Looking at the P-V diagram for an idea rocket engine, there's pressurization (1-->2), constant pressure combustion (2-->3), and isentropic expansion to ambient pressure (3-->4), which takes place in the nozzle. The two ways to crank up the area inside the curve (work of the cycle) are to drop your ambient pressure or increase your operating pressure (in reality, the nozzle expansion won't be completely isentropic, but its a close enough approximation). Ambient pressure is a function of, well, the ambient environment. The lower the pressure, the greater the work (and efficiency), this is why engines are more efficient in a vacuum (an underexpanded nozzle drives up your ambient pressure). Conversely, the chamber pressure can be controlled by the design. The Raptor engine is designed to run at 30 MPa. The RD-180 (Russian witchcraft engine) runs at about 25. The F-1 engine on the Saturn V was at 7, and therefore was much less efficient. Ramlaen and Collimatrix 2 Quote Link to comment Share on other sites More sharing options...
LostCosmonaut Posted November 7, 2018 Author Report Share Posted November 7, 2018 Falcon 9 upper stages are going to be made similar to BFR. https://twitter.com/elonmusk/status/1060253333116473344 Musk says it could be used to test reentry tech; https://twitter.com/elonmusk/status/1060265065276825601 Ramlaen 1 Quote Link to comment Share on other sites More sharing options...
Ramlaen Posted November 8, 2018 Report Share Posted November 8, 2018 Falcon Nine continues to undercut SpaceX's newer rockets. Quote Link to comment Share on other sites More sharing options...
LostCosmonaut Posted November 20, 2018 Author Report Share Posted November 20, 2018 BFR is now Starship (well, Super Heavy + Starship). There is some concern over the number of changes BFR seems to be going through. Regardless of whatever changes happen to the design, I am going to assume they will be keeping the 9m diameter, since they have already started cutting metal. Would be stupid to switch to completely new tooling at this point. Quote Link to comment Share on other sites More sharing options...
Sturgeon Posted January 11, 2019 Report Share Posted January 11, 2019 Starhopper is done. https://mobile.twitter.com/elonmusk/status/1083567087983964160 Belesarius, Zyklon, Ramlaen and 1 other 2 2 Quote Link to comment Share on other sites More sharing options...
Belesarius Posted January 11, 2019 Report Share Posted January 11, 2019 17 minutes ago, Sturgeon said: Starhopper is done. https://mobile.twitter.com/elonmusk/status/1083567087983964160 straight out of a 50s Heinlein cover. Quote Link to comment Share on other sites More sharing options...
LostCosmonaut Posted January 23, 2019 Author Report Share Posted January 23, 2019 Popular Mechanics interview with Musk on the BFR https://www.popularmechanics.com/space/rockets/a25953663/elon-musk-spacex-bfr-stainless-steel/ On the windward side, what I want to do is have the first-ever regenerative heat shield. A double-walled stainless shell—like a stainless-steel sandwich, essentially, with two layers. You just need, essentially, two layers that are joined with stringers. You flow either fuel or water in between the sandwich layer, and then you have micro-perforations on the outside—very tiny perforations—and you essentially bleed water, or you could bleed fuel, through the micro-perforations on the outside. You wouldn’t see them unless you got up close. But you use transpiration cooling to cool the windward side of the rocket. So the whole thing will still look fully chrome, like this cocktail shaker in front of us. But one side will be double-walled and that serves a double purpose, which is to stiffen the structure of the vehicle so it does not suffer from the fate of the Atlas. You have a heat shield that serves double duty as structure. Yeah. To the best of my knowledge this has never been proposed before. Ramlaen, Sturgeon and Zyklon 3 Quote Link to comment Share on other sites More sharing options...
Ramlaen Posted February 7, 2019 Report Share Posted February 7, 2019 Design requires at least 170 metric tons of force. Engine reached 172 mT & 257 bar chamber pressure with warm propellant, which means 10% to 20% more with deep cryo. Lord_James 1 Quote Link to comment Share on other sites More sharing options...
LostCosmonaut Posted March 18, 2019 Author Report Share Posted March 18, 2019 Per SpaceX, BFR heatshield will be a combination of hexagonal tiles, with transpirational cooling for areas of highest thermal load; https://twitter.com/elonmusk/status/1107378575924035584 Quote Link to comment Share on other sites More sharing options...
Ramlaen Posted March 25, 2019 Report Share Posted March 25, 2019 Quote Link to comment Share on other sites More sharing options...
Ramlaen Posted April 4, 2019 Report Share Posted April 4, 2019 LostCosmonaut 1 Quote Link to comment Share on other sites More sharing options...
Ramlaen Posted July 26, 2019 Report Share Posted July 26, 2019 Zyklon 1 Quote Link to comment Share on other sites More sharing options...
LostCosmonaut Posted August 4, 2019 Author Report Share Posted August 4, 2019 Starship announcement upcoming on August 24th; Quote Link to comment Share on other sites More sharing options...
Sturgeon Posted August 27, 2019 Report Share Posted August 27, 2019 Starhopper hopped successfully: Laviduce, Belesarius, Lord_James and 1 other 3 1 Quote Link to comment Share on other sites More sharing options...
Sturgeon Posted August 28, 2019 Report Share Posted August 28, 2019 Quote Link to comment Share on other sites More sharing options...
Ramlaen Posted August 29, 2019 Report Share Posted August 29, 2019 Lord_James 1 Quote Link to comment Share on other sites More sharing options...
Sturgeon Posted September 27, 2019 Report Share Posted September 27, 2019 We have been doing an awful job of keeping this thread up to day. Starship got stacked today: There's lots of other details about it on the discord. Ramlaen, Laviduce and Lord_James 3 Quote Link to comment Share on other sites More sharing options...
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