RedKraken

Ovchinin and Hague are now famous for surviving a launch failure.

Some cool work on trying to estimate the BE-4 performance : https://forum.nasaspaceflight.com/index.php?topic=45518.0 They are clustering around 312s - 345s for the isp based on the geometry, cycle, pressure and thrust. This estimate puts it just over RD-180 series performance at 311-337s. The TWR is a mystery. It is a massive powerhead. I figure it may be somewhere near 80:1 like the RD-180. Maybe more since the chamber pressure is so low : 13.4MPa vrs 26.7MPa on the russian engine. Less metal needed around the chamber. If so, the 240t thrust engine would have a mass of about 3t.

A small bfs could be exactly what we need considering its dry mass is sitting at about ~75/1200 or 6.25%. Its a lot more complicated than a kickstage....but it returns to base by itself. No orbital pickups. If scaling down works for the drag-o-dynamics of the bellyflop entry....and the drymass. Not sure about clustering these in a BFS. it might just be better to do a 1/5 BFR (or SFR)...roughly 880t GLOW and 28t LEO/ 8t GTO.. so GTO class missions don't interfere with moon/mars stuff. Which is essentially a super-capable Falcon9 replacement operating off falcon9 sized launch pads. I don't think we will see this anytime soon....but it is interesting to think about.

10 tonne probes to the outer planets is a beautiful thing.... i'd like to order a dozen please.

Good point. I guess it depends how fast you want them back. If you want them for another mission in two weeks time fast-turnaround, you spend the fuel. If you dont need them for a couple of months, your payload goes up from closer to 8t and do some aero-braking/burn combination. heh... i would hate to crush my beautiful gto-kicks....

Several folks have commented on kick stages and tugs for BFS cargo. Some stuff from reddit and NSF : https://www.reddit.com/r/SpaceXLounge/comments/7553za/wildass_speculation_thread_20_3b_whoops_i_dun/ https://www.reddit.com/r/spacex/comments/9hys4y/bfr_gto_trajectory_ideas_with_falcon_9like_kick/ https://forum.nasaspaceflight.com/index.php?topic=46412.0 I am interested in reusable methalox kickstage designs that can deliver a 7 tonne sat out to GTO (2500m/s), then 16 hrs later at perigee burn back into LEO (another 2500m/s sans payload) for a later pickup and return to surface. cluster while waiting for pickup in LEO can be carried in a carousel on bfs cargo Why return to surface? Refuel in orbit might be doable...but payload transfer from BFS to kick would be tricky. Would need an extra berthing system. Keep it simple. Just do integration and fueling on the ground and wear the price of lifting 5t extra dry-mass on your 120t lifter. For example 12t of sub-cooled methalox (tanks are ~2m long by 3.0m diameter or another combination with gives ~14 cubic meters of tank space), 1 tonne dry mass (~7.7%), 10t raptor (100kN, sea-level for simplicity - 356s in vacuum, mass ~50kg) Solar / batteries / apu for 16hrs of operation and maybe a few weeks of dormant operation while waiting for pickup. Boil-off management up-to 90 minutes for GTO burn fuel(~11t) and ~16hrs for LEO return fuel(~1.1t), maybe 150hrs for clustering fuel. various attitude and ullage thrusters payload up to 7t Total package ~20t. 2018 BFS cargo (120t LEO) could lift a carousel of 5 or 6 of these. Dump them in LEO, let them GTO burn when they are in position, pickup a cluster of spent kicks from the last mission, and return home for dinner. Ideas/Comments?

heh .... 1.67 twr off the pad for a ~800 tonne vehicle. Interested to see Arianne 6 ... 2020 is not that far away. And prometheus engine. But all eyes will be on BFS .... NewGlenn.... and chinese reuse rocket attempts......

Not sure Dal...sounds like the symptoms may be similar....unwanted gas in the liquid feed pipes ..... but very different magnitude. But i don't think cavitation bubbles would be big enough to block the mass flow. The engine would just run rough until something important breaks.

Aside from the sub-cooling density bonus... " it gets rid of any cavitation risk for the turbo pumps, and it makes it easier to feed a high pressure turbo pump if you have very cold propellant." - elon https://space.stackexchange.com/questions/18486/how-actually-do-sub-cooled-propellants-reduce-cavitation-within-turbo-pumps-an Elon mentioned it a couple of years back (IAC2016?) I wonder what the penalties are for trying the run the raptors on non-subcooled but still liquid propellant? Less mass flow and thrust for sure.....decreased life expectancy of pump parts? chugging - > exploding engine? https://en.wikipedia.org/wiki/Combustion_instability Chapter 10 of Sutton's Rocket Propulsion Elements : "It is important for pumps not cavitate during operation because cavitation produced bubbles reduce the steady nominal propellant mass flow and cause combustion instabilities"

I'd be surprised if they moved away from the 1.3m bell from the 2017 design. Changing to 30 MPa / 200t was a surprise.... but a welcome one. Are we talking ~2000kN? I thought elon would be talking metric tonnes. And 30/25 * 170t comes out at 204t for a very rough approximation. Are we still dealing with 334s - 361s isp of the 2016 engine?

Angara-5 flight2 news : http://www.russianspaceweb.com/angara5-flight2.html#2018_09 URM-1 prototype on the dynamic test stand .... the bundle of cables looks like instrumentation.

It doesn't matter to most people. Mostly harmless...alcohol/cigarettes and sugar are way more destructive. Weed products are super important to folks who self medicate for chronic pain/cancer/ms etc. Will he lose business for sparking up on-line? I don't know.

I may have the answer .... https://rossbainesart.bigcartel.com/product/j-r-elon-fine-art-print-a1-a2-a3

Hope elon does another technical ama on reddit. The last one was a data goldmine. Edit : I missed this : Here is Yuyu standing in the first barrel section : link : https://twitter.com/yousuck2020/status/1041877430942674944

The first 9m barrel section has been built.

"moon mission : spare parts ... just in case" .....the musicians can do some quick repairs....fire up the lem.

"First BFS to orbit in 2 or 3 years"

"Tin-tin rocket design"

Flight engine? Hopefully. I wonder how many seconds of test firing they are at.... Moon guy has been smoking blunts with Elon.

Gonna have to get some hard numbers on those raptor specs. Expansion ratio would be really helpful. 380s and 200 tonnes thrust in vacuum ?? NSF folkes suggest the increase to 30MPa chamber pressure gives 2MN at sea-level.....interesting. I wonder if they stayed with expansion ratio 40.....those bells still look unchanged at 1.3m diameter.

unmanned test launches...."a bunch"

Landing : "This will look really epic....."

"Vert stabiliser" is not a vert stabiliser.... its just a leg.

BFR 2018 #2 : ~1100 cubic meters cargo

BFR 2018 #1 : 100t to surface of mars