sevenperforce

This makes a lot of sense and would explain the pockets of high immunity, the apparent family-wide immunity and susceptibility patterns, and the overwhelming negative outcomes for people with PHCs. Also kiddie resistance. [snip]

The more I watch the Starship updates the more it feels like Elon is playing real-life KSP. "Oh, that part wasn't strong enough? Revert and swap it out with a stronger adapter. Did it work? Okay, now back to the VAB, add fins, and try again." Well, sending comsats to GTO is the biggest source of space-related revenue right now. With Starship we could launch 10 tonne comsats to GTO for under $10m per launch. And on each launch we can co-manifest five more equal-sized comsats, if we want, at no additional cost. Or not, because the cost is so low that it doesn't matter.

I actually messed it up even worse than that; I wrote the equation to take the mixture ratios as the volumetric ratios so it was all out of whack. BE-4 is methalox. Here's the corrected table. Engines bulk density (kg/m^3) Engine Thrust (kN) Weight (kg) isp_v (s) Length (m) Dia (m) prop mass, kg O/F ox fuel prop at mix Merlin 1D 914.1 470 311 - 0.91 - 2.34 1252 826 1084.5 RD-180 4152.0 5480 338 - 3.15 - 2.60 1141 810 1024.7 RL-10B-2-1 111.2 301 465.5 2.19 2.14 - 5.88 1141 71 357.6 RL-10C-1 101.9 150.5 449.7 2.19 1.45 - 5.50 1141 71 343.8 RL-10C-1-1 105.9 150.5 453.8 2.46 1.57 - 5.50 1141 71 343.8 RL-10C-2 111.2 301 465.5 2.19 1.86 - 5.50 1141 71 343.8 RL-10C-3 108.5 225.75 460.1 2.19 2.14 - 5.50 1141 71 343.8 Raptor Vac 2150.0 1826 380 6.60 5.81 - 3.80 1252 439 903.2 Raptor SL 1960.0 1500 350 - 1.30 - 3.80 1252 439 903.2 BE-4 SL 2400.0 5246 340 - 1.90 - 3.70 1141 423 837.9 BE-3U 710.0 1477 452 3.18 1.82 - 5.50 1141 71 343.8 Merlin 1D Vac 934.0 480 380 4.82 2.89 - 2.36 1252 826 1085.3 RS-25 (SSME) 2279.0 3526 452.3 - 2.44 - 6.00 1141 71 361.9 RS-68A 3556.0 6686 411 - 2.43 - 6.04 1141 71 363.3 SLS SRB 20000 113750 268 - - 625000 - - - - GEM-63XL 2026 5400 284 - - 48000 - - - - Hydrolox doesn't even break 400 kg/m3.

What do you mean? The J-2 absolutely had a vacuum nozzle.

More engine data... Engines bulk density (kg/m^3) Engine Thrust (kN) Weight (kg) isp_v (s) prop mass, kg O/F ox fuel prop at mix Merlin 1D 942 470 311 - 2.34 1252 826 1124.3 RD-180 4152 519 338 - 2.60 1141 810 1049.1 RL-10C-1 101.9 301 449.7 - 5.50 1141 709 1074.5 RL-10C-1-1 105.9 301 453.8 - 5.50 1141 709 1074.5 RL-10C-2 111.2 301 465.5 - 5.50 1141 709 1074.5 RL-10C-3 108.5 301 460.1 - 5.50 1141 709 1074.5 Raptor Vac 2150 1826 380 - 3.80 1252 439 1082.3 Raptor SL 1960 1500 350 - 3.80 1252 439 1082.3 BE-4 SL 2400 5246 340 - 3.70 1141 423 988.1 BE-3U 710 1477 452 - 5.50 1141 709 1074.5 Merlin 1D Vac 981 480 380 - 2.36 1252 826 1125.0 RS-25 (SSME) 2279 3526 452.3 - 6.00 1141 709 1079.2 RS-68A 3556 6686 411 - 6.00 1141 709 1079.2 SLS SRB 20000 113750 268 625000 - - - - GEM-63XL 2026 5400 284 48000 - - - - Interesting that the first stage of the New Glenn has the worst possible bulk prop density. I didn't realize how much hydrolox engines benefited from that high O/F ratio.

I went back and used actual numbers from the Apollo 17 mission Ascent Data to determine the real performance parameters for Saturn V. Drag likely includes propellant residuals. All values in m/s. Stage Onboard dV Drag Losses Effective dV S-IVB (TLI) 3122.0 82.1 3039.9 S-IVB (EOI) 1022.1 210.3 811.8 S-II 4746.9 547.4 4199.4 S-IC 3869.4 1087.6 2781.8 Vehicle 12760.3 1927.4 10832.9 Total payload to TLI was 48.6 tonnes. S-II was a friggin' workhorse.

UV-c would be great for disinfecting objects and surfaces which cannot readily be dunked in bleach or rubbing alcohol. For example, if hair salons want to reopen, they can do so if the beauticians pass an antibody test and all surfaces get zapped with 10 minutes of skin-blistering UV between each customer. UV-c does jack sh*t as a preventative or a treatment.

I hadn't either, not until a few months ago, but it REALLY simplifies calculations. Especially when you are working with real flight telemetry. No more piecewise integration. Yep, typo. Thanks. The actual number is 942 kN because I am using vac thrust for all engines.

Loss of thrust due to atmospheric pressure. Saves you the trouble of switching between SL specific impulse and vacuum specific impulse: just use the vacuum specific impulse and chalk losses up to thrust drag. The maths work. Also, here are some reference values for current or near-current engines that may be useful...some estimates in here but they are good ones. Engines Engine Thrust (kN) Weight (kg) isp_v (s) prop mass, kg (srb only) Merlin 1D 941.8 470 311 - RD-180 4152 519 338 - RL-10C-1 101.9 301 449.7 - RL-10C-1-1 105.9 301 453.8 - RL-10C-2 111.2 301 465.5 - RL-10C-3 108.5 301 460.1 - Raptor Vac 2150 1826 380 - Raptor SL 1960 1500 350 - BE-4 SL 2400 5246 340 - BE-3U 710 1477 452 - Merlin 1D Vac 934 480 380 - RS-25 (SSME) 2279 3526 452.3 - RS-68A 3556 6686 411 - SLS SRB 20000 113750 268 625000 GEM-63XL 2026 5400 284 48000

You can also use fewer kerolox engines on the first stage if you have the SRBs to help you off the pad. I dislike SRBs but they're useful for that. Some useful reference values for anyone looking at what performance you need to get to the moon... The Saturn V S-IC first stage accelerated the vehicle to 2.06 km/s and lost 1.85 km/s to gravity drag, aerodynamic drag, and thrust drag The Saturn V S-II second stage accelerated the vehicle to an additional 3.55 km/s and lost 1.24 km/s to gravity drag The Saturn V S-IVB third stage added 2.18 km/s to reach an earth parking orbit of 191.2 km The Saturn V S-IVB third stage restarted to provide 2.17 km/s for the trans-lunar injection. So you can start there.

Smash to remove, I suppose?

This topic got me thinking more about how different kinds of propellants are more or less efficient and effective for different applications. What IS the most efficient way to get a bunch of mass to the moon, assuming an expendable vehicle? How do you measure efficiency? How many staging events are too many? If we were to build a better Saturn V today, we would once again try to spread the costs across as many contractors as possible. So it would not be surprising to have two or even three different propellant choices. Plumbing the pad for even more multiple prop feeds is expensive but is something they'd absolutely do. My gut says that for sending a 100-150 tonne payload to the moon (or the equivalent for a Mars/Venus direct flyby), the beefiest, most powerful approach would be to do 3.5 stages: kerolox with strap-on SRBs, a methalox second stage, and a hydrolox third stage. Probably RD-180s or Merlin 1Ds on the first stage, probably a couple of vacuum Raptors on the second stage, and probably BE-3Us for the third stage. But is the thrust advantage of a kerolox first stage obviated by using SRBs in parallel? Is the ideal expendable moon rocket really just a bigger Vulcan? One advantage to going kerolox-methalox-hydrolox is you can use a common tank diameter all the way up.

Curiouser and curiouser. Definitely no bolt-holes.

Thanks @mystifeid. I like the fine control provided by Squad -- I am doing some amazing things with abort modes right now on my increasingly granular Apollo 17 mission -- but if they set up a little lower barrier of entry it would be nice.

I have not built any prop planes with the new parts -- do they need the KAL-3000? How do you start them?

591 parts and burgeoning.

FYI: Unless you are using a fairing, part clipping does nothing whatsoever for drag, only for vehicle stability.

Reminds me of this: https://www.cnbc.com/2020/04/22/she-got-a-paycheck-protection-loan-her-employees-hate-her-for-it.html For certain narrow income ranges, you can temporarily make more money off unemployment than via PPL.

Just came to post that.

I am currently only using my SUV for potatoes and other groceries due to the shutdown. But the SUV was designed from the beginning to be safe enough to use for my kids. Should I throw away the SUV and buy a pickup for grocery runs until the pandemic is over?

Last I checked, truck beds are not rated for adult passengers either, though that doesn't stop rednecks. The fact remains: if you have reusable vehicles, it makes no economic sense to develop, build, and maintain an entirely separate model for launching lower-value payload if your higher-rated payload will do the same job. If you have expendable vehicles then it depends on how modular your components are. I never learn my lesson. Exactly.

A pickup truck bed is not rated for strapping down infant carseats.

I have a well-maintained, high-safety-rated SUV with top-of-the-line, nuclear-holocaust-proof carseats that I use to haul my kids around (when the world is open). If I remove the carseats and fold the back rows down, I can fit a full-size dining room table plus chairs in the back end. It wouldn't be "cheaper" for me to buy and maintain a separate pickup truck for hauling cargo merely because the SUV has a higher child safety rating than the pickup truck. Similarly, if SpaceX's man-rated launcher can send cargo to space, why would they develop a second, non-man-rated one to do the exact same job?

Citation needed that it would be cheaper to maintain a different, non-man-rated rocket for unmanned launches.

[Citation needed] Yes, I know, lol.