RedKraken

T+10:30 fregate burning now. All nominal.

http://www.arianespace.com/mission/ariane-flight-vs20/ T - 4 min

GSAT-7A mission success.

from NSF

Delta IV scrub

From Trevor Mahlmann https://twitter.com/TrevorMahlmann/status/1074291572475289610

Mission complete. Congrats.

orbit. 40min to burn by curie kick.

Electron launch now. https://www.rocketlabusa.com/live-stream meco. stage 2 is on its way.

Wow....thats a hydrogen leak out the top of the powerhead ?? NSF guys think its close to the high pressure fuel turbopump. They let it go for many seconds (30s?) before shutting down. Strange the engine controller didn't pick up the problem on its telemetry. https://twitter.com/nextspaceflight/status/1072966252170305536/video/1

Electron launch in 6 hours.

NROL-71 launching Hold....

Chang'e 4 launch replay :

SSO-A yesterday. Ariane today. CRS-16 at the cape tomorrow, then Chang'e 4 at xichang , then NROL-71 at vandy. Launch fever.

This is smart. The core chews propellant at half the rate of the boosters. It will have 50% of its load left by sep, more if they throttle back. The boosters do the hard work. The core's job is to save as much fuel as it can for sep. I figure this thing has a mass of 3500 tonne and could lift 115 tonne to leo with just the first 3 stages. And 36 tonne TLI. Should be able to put federation + prop unit (20t) into LLO with stage 4(11t). The boosters hold maybe 440 tonnes of kerolox (45t dry) and measure 40m x 4m. Booster sep is staggered i think? 4 then 2. Same for the core (stage2). Core might have 280t of prop at sep. (68tdry..has to be strengthened for boosters) The hydrolox stage3 could be 75 tonnes(10 dry), 22x4m, but has tiny RD-0146 engines which max out at 7 tonne thrust each. Isp 470s ? cool. They only have to circ for leo, and punch TLI or TMI, so i guess twr 0.15 is ok. Longest TLI burn ever. Stage 4 is about 10 tonne of kerolox with a rd -058mv. 4m x ~3m? With fed spacecraft on top at 20t this combo might have ~1200 m/s. Feels like TLI course adjusts / Luna insertion with Stage 4. Punch home with storables in the fed propulsion module (1000m/s).

Zuma was really low. 4500->2800kph in 17s. (1250 - 778) + (9.8*17s) = 640 m/s https://www.youtube.com/watch?v=NQVNSwTz3qg&t=20m

Okay : SOACOM 1A from oct 7 VAFB 4520kph -> 2122kph in 26s, altitude 55km ->31km This is (1255m/s - 583m/s) + (9.8* 26s) = 672 + 255 = 927 m/s ..... closer to your 800 m/s https://www.youtube.com/watch?v=zw4X8p5zVZE&t=6m

I'll see if i can find the video showing the booster velocity during the brakeburn....it was pretty amazing to me. The velocity got chopped from 1600m/s down to 700 m/s in about 20s. Occurs about T+6min, or about 60s before the landing. They call it the "re-entry burn" in the webcasts.

Meco at +1200m/s, + 1200m/s for a bunch of RTLS (at about +100km downrange, +60km alt). At +1200m/s in the horizontal, i need -1200m/s(WRONG! way too much) to get back to the launch site.... ....if my return time was (100000/1200) 83s, but it isnt...oh boy i've stuffed up. Actual return flight time is loft(1200/9.8)122s up to 130km + descent time estimate (from 130km) is about 160s going 1600m/s if no drag/ no vert burns) So about 280s....check landing time for booster should be around (150+280) T+430s or 7m10s.... CRS-13 booster landed at 7m40s..cool. Say 300s for simplicity. Estimate we use a 30s boostback burn from 100km downrange to 110km downrange. So at meco I burn -1200m/s to zero my horizontal velocity, then only another (110km/270s) -400m/s to hit the pad... All up 1600m/s burned in the horizontal instead of 2400. Ouch. So my new RTLS deltaV =1.35Vhmeco(boostback) +1200(brakeburn) +200(landing) m/s assuming meco at (+1200m/s, +1200m/s) or 1700m/s prograde That brings RTLS reserve down from 16% to 11%. Nice! Or 43t for the F9 booster. The boostback burn is not instantaneous. Estimate (say 66t->40t) 26t of propellant reserve burned at 311s. 26t on three engines at 300kg/s each is about (26/0.9)29s of horizontal burntime. Close to my estimate above. Good. For (0.75x29)22s of this we are still heading downrange at an average of (1200/2)600m/s. 22s at 600m/s is 13200m. So 13km further downrange from burn start 100km (~113km) Also close to estimate. After a 29s burn we are heading home at 400m/s from 113km downrange with another 90s before we start descending and 300s before we land. ****I need to recheck my math and test this against some telemetry.

More explicitly : For RTLS I figured deltaV is 2 x (Vh @ meco) + (20s Brakeburn sheds 1000m/s + 20x9.8 g loss ) + (3s landing burn sheds 170m/s + 3x9.8 g loss) Roughly 2 x (1300m/s) + (1200 m/s) + 200m/s. Or 4000m/s. Most of that occurs at boostback 311s isp. The brakeburn at whatever its burn average isp is : guess 300 s. Landing burn isp at 282 s. Use a weight average isp of 305s for the lot. So 23t final mass (plus margin if required), 4000m/s deltaV, 305s isp gives a start mass of 87.7t. Fuel fraction is (87.7 - 23 ) / 411 = 0.157 Reserve is 15.7% If you need a margin, bump up the reserve. 17% reserve lets you land with 2t of propellant left. 19% reserve lands with 5t left. No boostback for ASDS, just a much bigger (~2x) brakeburn.

congrats

I've been using 8% and 16% based on the horizontal component of the velocity at meco.

I can't see elon getting excited about that. andyonions on reddit suggests a Kevlar/CF hybrid. https://www.reddit.com/r/SpaceXLounge/comments/a0dev6/contour_remains_approx_same_but_fundamental/?sort=confidence

Irtysh. http://www.russianspaceweb.com/index.html Unrelated but super interesting : Soyuz control software described by one of the developers (gosha_space) : https://forum.nasaspaceflight.com/index.php?topic=46594.0 The control system of Soyuz-TM is written in Fortran and Algol. Soyuz-TMA (and TMA-M) in Assembler (45,000 lines) and Pascal (37,000 lines). Real-time operating systems are used only in simulators in the Cosmonauts Training Center (Linux-based QNX). The station for testing the Union (there is a program on the RSK1 computer) also uses a real-time OS based on Linux.