sevenperforce

LOL, just came over to post this. So, did we just not see the underlying structure for the other components, or is the underskin limited to the lower sections? I could foresee near-balloon-tank upper section but reinforced lower. Or we could be looking at something that will not translate at all to the orbital version. Yes, but if they can use pumped props across the entire body instead of a tracked ballast sled...well, that would be epic. Upper limit is established by TWR, based on engine thrust.

Maybe they realized that the weight of systems needed to actuate the moving parts would be so great that they could as easily introduce heavy pumps and bulkheads to move fuel mass around inside, changing CoM as desired. I've actually done something like that in KSP.

I would assume that welds strong enough to hold aero will be good enough to pump full of props. The view looking down that crew arm.........

It's a friggin' spaceship. At 4.2 km/s (understand, that's if they top the tanks all the way to GLOW limits, rather than using small internal tanks), this thing can accelerate to over 100 km, then fire its engines all the way back down to a soft landing.

Per edit above, I have no idea where I got 204 tonnes. Three SL Raptors can lift 611 tonnes. If SpaceX wants a 1.5 TWR on liftoff, then GLOW is 407 tonnes. Your number comes to a dry mass of 110 tonnes, representing 29% mass growth over the composite 2017 IAC version (which was bigger and included a cabin) so that is conservative enough to cover any other issues. This will be mass-limited before it is volume-limited (since tankage volume is not significantly less than the full-size version). Doing the math, that gives 4.2 km/s of dV. That's twice what you need to do a suborbital hop.

Aaaaaand then everyone around him resents him, sets out to f*** him over, and he ends up quitting in tears after 2 weeks. With only three engines, there is probably a hard limit on liftoff mass (TWR>1) before any structural limitations on the steel superstructure or volumetric limitations on tankage. By my MSPaint magic, the engine bells are 87:608 pixels (in one image) which comes to 0.1466:1, which comes to 1.32m diameter on these raptors if the body diameter is the expected 9 meters. These are full-size Raptors. 2 MN each. 6 MN total liftoff thrust. Maximum takeoff mass 204 tonnes. Wait, where the heck did I get 204 tonnes? 6 MN / g = 611 tonnes!

I will bet hard money that the raptors are 100% real. But yeah, this is ridiculously cheap construction. I am thinking that some intern at SpaceX was like "Hey, look -- if we build this out of sheet metal then it will do the same job and be 10% the cost" and Elon was like "OKAY EVERYBODY LISTEN UP" Someone who has more free time than me should take the quoted thrust of the Raptors, the estimated mass of stainless steel in the visible configuration, and look at what kind of dV the existing hopper can expect to achieve.

Elon got his subassembly right and the attachment node connected! I would disagree, since Elon has talked about suborbital hops in 2019 (though, again, Elon Time)...but without articulation on the finlegs, I don't see how this does anything other than lawn-dart on re-entry. Then again, Elon has hinted that there are radical changes for the stainless steel StarShip. Who knows -- maybe articulating finlegs is a bridge too far and the SpaceX aerophysics team has come up with a way to effect multiplanetary hypersonic lifting-body reusable re-entry sans moving parts.

Apparently Elon Time finally downloaded the Ludicrous update.

They are literally assembling a rocket in a big open field with sheet metal. I can't even.

StarShip has far better lifting characteristics than the Apollo CM and a wider allowable AoA than the Shuttle. Are we assuming the holes cut in the central column are for thrusters?

When people ask "why can't spaceships go at light speed" they may be asking multiple questions. Your (excellent) answer illustrates that sometimes you don't have to go into the details of relativity, because the biggest teaching point is that space is HUGE. The distances between everything in the universe are IMMENSE. Consider: the farthest that human beings have ever traveled from Earth was during the Apollo 13 mission, when Lovell, Swigert, and Haise took an extra-wide swingaround past the far side of the moon. At apogee, they were 407,000 km from Earth...a distance that would take a NASCAR stock vehicle more than seven weeks to traverse, traveling at top speed. Yet that distance pales in comparison to the size of the solar system. If the solar system (as defined by the orbit of Neptune) was the size of Paris, France, then that 407,000 km would less than two feet. And at that scale, the outer limits of our solar system (defined by the Oort cloud) would be three times the size of our planet. The speed of light has very little to do with it. The major issue is that space is really, really, ridiculously big.

WE WANT PICTURES!

Posting this here in the hopes that someone has more expansive medical science chops than me and can shed some light on this. There are a whole host of certifiably fake diseases out there, which usually go by names like "chronic candida", "adrenal fatigue", "non-celiac gluten sensitivity", and the lovely "[Wilson's Temperature Syndrome](https://sciencebasedmedicine.org/naturopathy-vs-science-fake-diseases/)" (which is supposed to be some chronic thyroid dysfunction). With a perpetually hypochondriac parent who bounced from fake disease to fake disease for my entire life, I am familiar with many of these. My elementary-aged oldest son has high-functioning autism. We reject pseudoscientific nonsense about vaccine injuries; all of our kids are fully immunized. My son has tested positive for food allergies in the past, but only peanuts appear to prompt serious reactions. He recently began exhibiting some persistent edema and irritation in his extremities; we took him to the pediatrician and she was unable to diagnose but did do some blood tests. He came back positive for exposure to Lyme disease, so we started him on antibiotics. He has an upcoming appointment with a specialist referred by the pediatrician. My wife has become very interested in the AIP (auto-immune protocol) diet and a lot of surrounding ideas. It has every indication of typical quackery, but despite significant searching I haven't been able to find any actual doctor giving a comprehensive discussion of it. It focuses on identifying "inflammatory foods" and eliminating them from the diet. I haven't been able to find any actual explanation of how the numerous lists of foods to avoid or include are generated, or what is actually supposed to make something an "inflammatory" food. Of course it has glowing reviews; if you eliminate 70% of your diet, you're likely to see SOME difference in your life, if only due to having more regular meals because you now have to plan everything days in advance. Is there a doctor in the house who can shed some insight into "leaky gut syndrome" and the auto-immune protocol diet? Or even anyone with better google-fu than me?

Lots of good answers so far. Here's another way of looking at it. How much is 2+2? Well, it's 4, obviously. And for thousands of years, we could all readily pick up two rocks or marbles or blades of grass, combine them with another two, and count find out that 2 + 2 does indeed equal 4. But suppose someone decided to really measure it. Like, super precisely. Far more precisely than you'd ever need for ordinary applications. They had this whole massive system of lasers and whatnot and they sat down and they measured and they realized, suddenly, that 2 + 2 is not 4. Instead, they found, 2 + 2 = 3.9999999999999437. It would be a shocking result, and everyone would initially expect it was some sort of error with the measurement apparatus. So someone else designed a different system, and they measured, and they found that 2 + 2 = 3.9999999999999435. So they tried again, and again, and with many different ways of measuring over many years, they ended up with the consistent answer that 2 + 2 is actually ever so slightly less than 4. That's what happened with relativity. We had been measuring things in very straightforward ways ever since Galileo and Newton, and then Einstein came along and said "Hold up, we haven't been measuring things closely enough; it's actually just a little different, and once you have a lot of mass or are going very fast then it gets more and more noticeable." As counter-intuitive as it is, measurements and speed and energy all start to warp when you look really really closely, because the things we are measuring (space and time) have a fabric all their own, and that fabric ends up getting stuck to what we are using to measure them. One consequence of this: When you push things to nearly a million times the speed of sound, space and time get so twisted up together that adding more thrust slows your perception of time but doesn't actually make you move any faster. That upper speed limit also happens to be the speed we perceive light as moving.

If it can't manage a load under suspension, that would be bad.

If they can get unlined COPV to work for LOX, I imagine stainless will be no problem.

All good info. Syntin is similar to RP-1 but has higher density and lower viscosity, both of which make it easier to ignite via spark ignition. Moreover (as I understand it), the pyro-ignited mains used syntin+LOX while the spark-ignited verniers used syntin+GOX with a preheater (as you note above) which also aids in spark ignition. Running on GOX for the mains is not really feasible because of flow issues; you can't get very good thrust. To spark-ignite actual kerolox in a large main engine, you pretty much have to use a staged igniter a la SSME and you have to figure out a way to vaporize the kerosene, which is not easy. Gasoline (petrol) is much easier to vaporize than kerosene...one reason kerosene is much safer. You can't do FRSC with a kerosene-similar fuel because of coking. Internal load-bearing structure doesn't preclude a monocoque tank; there's no reason they can't fill it straight up. This is a flight article; it needs a load-bearing member for landing. At landing, the lower portion of the tank (and the engine thrust structure) is all effectively suspended from the top of the legs. I anticipate internal trusses mating the thrust structure to the lower leg braces as well, so that the overall body has both compressive and tensile load-bearing capacity. This may be one of the reasons they decided to make the switch back from composites to steel. Composites have better pressure-bearing capacity in terms of mass budget, but since the StarShip is not pressure-fed, it makes more sense to prioritize dynamic load-bearing, where steel blows composites away. Sure, that's possible. Not necessary, though. They seem to be spending quite a bit of time welding and polishing the outside if it's not going to be pressurized.

If Elon's past boasts are any indication, the current starship being assembled in Boca has orbital capacity but will not be used as such. Word. Still better than dealing with TEA-TEB. And pilot flames are a non-issue. The SSME is/was a FRSC (fuel-rich staged combustion) engine which used an augmented-spark igniter. If you have an augmentation igniter, you can ignite any time you want. If you are igniting via dual preburners in the main combustion chamber, that's a touch more challenging...but it is the sort of thing that can be readily tested. The J-2 used an augmented spark igniter. Very easily. Hot-gas meth-oxy thrusters are hella easy to ignite. Case in point: your gas stove at home. --------------------- For the record... Yes, spark ignition of kerolox is a non-starter. No one is suggesting spark ignition of kerolox. Next topic.

TBH if I had an insurance black box I would have much more fun driving because I would be hella careful and it would become a whole thing. My jurisdiction only has one single car inspection site run 100% by the government. It is annoying when you need to get your car inspected, yes, but it means you don't have to worry about getting scammed by a excrementsty tire-and-lube shop that will pretend you're failing just to drain you. And the inspection station is a half-hour wait at 6 AM. I assume it is worse during the day; I haven't tried. There is a speed-trap camera in my city that made six figures in ONE MONTH last year. That is scary AF. I have driven quite a few moving trucks in my time, and speed governors are 100% BS. I hate them. "Hey, sorry, you hit 69 mph and so now we are going to cut the throttle."

Yes, that is what I meant. SpaceShip will use 10-tonne-class hot-gas bipropellant rocket motors, pressure-fed from the header tanks and spark-ignited. As opposed to cold gas, where the exhaust is simply gas under pressure. Spark ignition works on larger scales, too. Like Raptor. And SSMEs.

Elon was tweeting recently about the regenerative braking on Teslas, which is pretty awesome, though not any differently than with any hybrid. Run the motors and drain the battery, and the car moves; invert, and you charge the battery while slowing the car. The Starship already has hot-gas RCS motors fed from the header tanks, which are autogenously pressurized by the actively-cooled engine bells. It will also need electric batteries to run onboard systems and provide for spark ignition. Presumably, the working fluid in the actively-cooled heatshield will be circulated by electric motors. A heat cycle and dynamo is a Carnot engine. Thus, methane could run through the loops while oriented belly-sunward to pressurize the header tanks, and then recirculated while in the opposite orientation to condense the methane back down to a liquid. Two different Carnot cycles so you can generate power from both. Same deal during re-entry.

You know, this is spectacularly ambitious speculation, but... ...what if the actively-cooled stainless-steel skin acted as a radiator and condenser on orbit?

I am curious to know how exactly SpaceX plans to pump methane through an actively-cooled windward Starship skin. Analogy to expander cycle?

Yes, the NIF achieved baseline positive energy balance, in that the net fusion output was greater than the energy delivered to the target. Of course the net fusion energy output was still only ~10% of the laser pulse energy and a smaller fraction of total system energy. Since none of the fusion energy was capturable, the actual energy balance was 0%. Inertial confinement has always been the most direct approach to fusion; if you get something hot enough, it will eventually fuse. The challenge is achieving ignition and actual power generation; we are decades away from that, at best.