sevenperforce

What do the engine thrust plates do that you can't do with a standard fairing? Does anyone have a MH partlist yet?

You'll never change me! Physicists with longitudinal Z-axes forever! Yeah, very nice. I'm sure people will do a pair of linear thrusters keyed to fore/aft translation only, near the nose. Then your main engine can be used for forward translation.

The original six-engined BFS article had really anemic TWR at SL and would have required all four vacuum engines firing (Elon: "Not recommended, but it'll do in a pinch") to get a successful pad abort from booster RUD. They added a third SL engine to the plans, to improve pad abort, to add another engine-out landing capability, and to improve downmass. Upping SL thrust by 50% could make the difference between one-way SSTO and SSTO with landing residuals.

The Mk3 crew capsule has roll, pitch, yaw, and X-Y translation thrusters, but no Z-axis translation thrusters. Of course you can easily enough orient normal to your prograde and then use X-Y translation to thrust prograde or retrograde. But most players will need a couple of linear thrusters for docking maneuvers.

Unfortunately, Tweakscale scales the new decouplers by percentage rather than by diameter.

The steerable personal chutes are badass though.

IIRC, he said that the tanker variant COULD theoretically SSTO, and he also said separately that they were planning to do EDL tests with the first test article, and people assumed he meant the two together. Suborbital hops are enough for EDL tests.

I must have been playing an older version than I thought.

The new telescope part requires active power generation, a large antenna, and a solar orbit. Not sure what it does beyond that though.

And also I can turn off those damnable interstage nodes! How did I not know this? Okay, new Tweakscale is back up and running, and it works with the new reskinnable tanks. Unfortunately Tweakscale does not function on the new R-series tanks, and it is broken on the old Donut tank. That sucks. I really love those tanks, too. The collision box is fixed on the new donut tank, though! Collision boxes are correct on all the new decouplers and separators, too...so we've got Atlas! There's a new telescope part......

Just tested it. This is...the best thing ever.

And realistic mass balancing.

WAIT WHAT HOW DID I NOT KNOW THIS I use advanced tweakables, so...if I have been missing this for all this time I feel VERY stupid.

Downloaded 1.4. Okay, let's see here. 2.5-m tanks have limited reskins. Nodes on the donut are changed, but we have two new radial-only balloon tanks. My old version of Tweakscale is broken but I'm sure a new version is out. Now if I can only remember how it installs... The new 2.5-m capsule is nice. The old one was way too heavy. New fairing color options are cool and all, but what's wrong with plain white? And I really wish we had the option for fairings to come apart without shredding.

Grasshopper test vehicle will likely have three SL Raptors but no vacuum Raptors.

Twice the thrust, but not quite so wide. Saturn V was 10 meters across at its base, without fins or engine shrouds; BFR is 9 meters. He means that humanity as a whole achieves a stable give-and-take relationship with AI.

No worries; I was adding, not correcting. Right. I just like to remind people that the limit you approach is the theoretical total chemical potential energy of the propellants. You cannot generate more impulse than the chemical potential of your propellant allows. Well, yes, that was oversimplified. The math isn't far off; technically, the square of the exhaust Mach number is proportional to a function of the ratio of chamber pressure to outlet pressure, for a given propellant, such that the isp scales with pressure drop for most propellant combinations, up to the theoretical maximum isp for that propellant. But I didn't mean to imply that this provides even a first-order approximation of actual thermodynamic efficiency, only that it represents the scaling function between pressure drop and isp. The larger the pressure drop between chamber and outlet, the more thrust and isp you can squeeze out of your exhaust flow at any given expansion ratio. Another issue: the limiting factor for chamber pressure is less often the chamber wall burst pressure and more often the engine cycle. You have to be able to get your propellants inside the chamber, after all. If you use a pressure-fed engine, you have to have tanks which can handle a greater pressure than your chamber. If you use a turbopump, you need power to run that turbopump. A gas-generator turbopump is the most straightforward way of doing it, but if you run too much propellant through your turbopump, you have less available propellant to actually burn in your engine. An expander cycle is more efficient, but is constrained by the specific heat of your fuel and the surface area of your exhaust bell. Staged combustion is best for supplying both high turbopump power and high efficiency, but it is terribly hard to get right. SpaceX's Merlin engine has successfully uprated its turbopump speed multiple times, permitting higher flow and higher power. This has boosted Merlin thrust and Merlin isp over the years.

Yeah, the video is slowed down. It took 40 frames to drop 125 pixels, diagonally. The stage height appears to be 54 pixels, again diagonally (thanks Pythagoras). The core is the same height as a standard Falcon 9, or 47.7 meters, and YouTube plays at 24 frames per second, so this says it fell 111 meters in 1.7 seconds, for an average observed speed of 65 m/s or 145 mph. Elon said that the core hit the water at 300 mph so it's probably at half speed. If you go frame by frame you can see that every other frame is interpolated. But yeah, very very steep. Surprisingly so. **sniff**

"But it would be so cool if we lived in a world where free energy and telekinesis and extreme longevity were real!" Or we could just look around at this world. The fastest animal alive today is a small carnivorous dinosaur, Falco peregrinus, which preys mainly on other dinosaurs, striking and killing them in midair with its powerful hind claws. Our species successfully completed a campaign to utterly annihilate a deadly microbe called Variola major that threatened to destroy us, and we did it by hijacking our own bodies with science. We landed humans on the largest relative moon in our solar system and brought them back. Our only natural satellite is precisely the right size and in precisely the right orbit that we are able to directly observe the corona of our star with surprising regularity. We figured out how to collect subatomic particles produced only during the dying breath of a collapsing supergiant star billions of years ago, and split them apart to get power for our homes. We just sent a freaking car to another planet on a giant missile, which we powered by releasing sunlight that had been trapped underground for hundreds of millions of years. This is a pretty cool world. I'd much rather live in a world where vaccines, dinosaurs, and the moon landing are real and free energy is a deceitful conspiracy than a world where free energy is real but vaccines, dinosaurs, and the moon landing are conspiracies.

Actually, an afterburning jet engine does accelerate exhaust gases beyond the speed of sound, so it has a converging-diverging de Laval nozzle like a rocket. The problem, though, is that the same nozzle also needs to work in "dry" mode with the afterburner off, when the exhaust gases are moving slower than Mach 1. So most afterburning turbofans have a complex tulip-like nozzle that can change shape, from converging in dry mode to converging-diverging in wet mode. The outside still looks generally like a tube, though:

BFR, or BFS? On the topic of BFR, I made my kids a scale model of BFR/BFS, complete with magnetic couplings to hold the two stages together: Still haven't decided how to fabricate little engines...

As a physicist, I can say that this is approximately equivalent to saying, "No one has yet tested whether cupcakes are spontaneously generated on the moon when Donald Trump hums Waltzing Matilda while dangling upside-down from the third ray on the Statue of Liberty's crown." Technically it is true, but that doesn't make the spontaneous generation of cupcakes any less a violation of the laws of physics. Likewise, no amount of yet-untested manipulation of jerk in an inertial system is going to create momentum from nothing. ...thats one hack of a red flag! Right? Like the guy said -- he'd happily promise a Nobel Prize, despite having no capability to generate one, simply because if you can overturn the basic laws of physics, you are guaranteed to get a Nobel.

Interesting. This means any sort of rendezvous and docking is right out.

Not actually no. More like, coincidentally yes.

Reminds me of a delightful party fact... Did you know the size of the Space Shuttle was determined based on the size of a horse's rear end? It's true. The wingspan of the Shuttle was constrained by aerodynamic considerations centered around the size of the Shuttle SRBs. The SRBs were the maximum diameter cylinder that could be carried by standard rail, since the STS was a big pork project that used contractors all around the country. The maximum size of standard rail is dependent on tunnel size, and rail tunnels were cut based on track width. Standard train tracks in the US are exactly 4 feet, 8.5 inches wide (1,435 mm). Why such an strange number? Well, train tracks were designed based on the standard size of a wagon axle. Wagon axles were, as a rule, precisely 4 feet, 8.5 inches wide, because that was the size of the ruts that formed in dirt roadways; a cart or wagon with a nonstandard axle width would not fit in existing ruts and thus would not be able to navigate. Why were ruts in American roadways exactly 4 feet, 8.5 inches wide? Well, that was the size of the wagon and cart axles imported from Great Britain. And in Great Britain, the wagon and cart axles were 4'8.5" because that was the size of the ruts in dirt roads in England. Why were ruts in British roadways 4'8.5"? Well, because the Romans had built the roads in the British Isles, of course. All Roman roadways were designed to accommodate axles of exactly 5 pedes. One Roman pes is 287 mm. And why? Well, the Romans had determined that an axle of 5 pedes was precisely wide enough for a two-horse chariot. So the size of the Space Shuttle was based on the width of a horse's posterior. Note: I make no affirmative claim that the foregoing is actually true. Repeat at your own risk.