Silavite

Looks like the engine config is confirmed (or perhaps I missed an earlier confirmation).

Communication issues aside, that looked like a pretty successful flight. Major props to Virgin Galactic!

I think that most discussion around life extension centers around eliminating damage caused by aging, thus causing the chance of mortality per year to remain constant rather than increase. (Or at least making sure that mortality chance does not increase with age due to biological factors.) https://en.m.wikipedia.org/wiki/Biological_immortality

I'm guessing that the launch tower will lose it's record as the tallest structure in South Texas to the soon-to-be-built lightning towers...

What kind of injector did the XLR99 use? Searching for documents or photos has not been fruitful thus far.

I wonder if that convention came from atmospheric science (given that emissions is connected to atmospheric chemistry) since water vapor mixing ratio is commonly stated in g/kg.

On-topic, what is the current dry mass for early articles? I see 120 tonnes listed as a target, and an Elon Tweet says ~200 tonnes, but that's from almost 2 years ago (Sept 2019).

This reminds me of when I was reading George P. Sutton's obituary (the author of Rocket Propulsion Elements):

My understanding is that the main issue with nuclear fission is the immense up front cost and time it takes to build plants. In the U.S. at least, there is even a negative learning curve for the cost of building a given design (later plants constructed with a given design will cost more than earlier plants—in direct contradiction to the idea of economies of scale helping to push costs down). https://energy.mit.edu/news/building-nuclear-power-plants/ The issue is partially regulatory, but it seems like there are other factors at play at well (more detail is in the article/paper).

I'm in Orlando today for a connecting flight which is scheduled to take off at 1:45, and the Starlink launch is scheduled for 3. Never more have I wanted a flight to be delayed.

SLS being ahead of schedule isn't something you hear about every day, but I'll certainly take it.

Today I discovered the wonderous program which is CEA (Chemical Equilibrium with Applications), and I'm unsure as to what some of the outputs are. Here's an example of what I mean using CH4 and O2 What are: (dLV/dLP)t (dLV/dLP)p M, (1/n) SON VEL,M/SEC I suspect M is related to molecular weight and SON VEL is the velocity of... something, but that's as much as I can figure.

I'm not sure that stability is an issue. As long as the time constant for a perturbation away from the velocity vector isn't *too* quick, the flight controller in concert with TVC should be able to keep the vehicle pointed the right way. I would wager that most launch vehicles today are statically unstable.

Splashdown!

The idea of a BE-4 modified for hydrolox has some precedent in the LR87, since it was originally designed for kerolox and then was made to use hydrolox and storables in separate variants. That said, the LR87 used a relatively simple gas generator cycle as opposed of the BE-4's oxidizer rich staged combustion cycle. In addition, most hydrolox staged combustion engines (save for perhaps the RD-701) use fuel rich staged combustion. Perhaps it would be possible to stick with the oxidizer rich cycle, but modifying a staged combustion engine to burn different fuel seems (to my untrained eye) like it would be difficult.

If I'm understanding the argument correctly: There have been plenty of reentry vehicles, yet none are cylindrical. The cylinder would have been used it were a viable shape. The cylinder hasn't been used historically, ergo it is likely unsound. I think that arguing from the perspective of historical trends isn't necessarily sound in this case. I would argue that capsules have been predominant due to their stability without active control surfaces (only a CG shift and RCS are necessary). Among reentry vehicles with active control surfaces, all thus far have utilized lift to glide to a horizontal landing (X-15, Dyna-soar, MiG-105, Buran, STS, X-37B). Therefore, Starship's rather unique method of landing (descent at 90 degrees AoA and then vertical propulsive landing) makes the comparison to other vehicles (which utilize lift during the terminal phase) invalid. If I may flip this conversation for a moment: Does @kerbiloid have a dynamical or thermal reason as to why the cylindrical body is unsound?

True, though STS-1 did have a bit of a close call during reentry due to issues with real gas modeling not matching the actual dynamics of reentry.

I believe that the cylinder would have less drag, but Starship's mass/area at reentry is more or less comparable with the STS. Some quick and dirty drawing with MS Paint gives an area of 370 m2 of the STS' underside, and a very crude estimate of its reentry mass (from subtracting LEO payload from MTOW on Wikipedia) would be 86 tonnes, which gives a mass/area of 232 kg/m2. I think that the projected dry mass for Starship right now is 130(?) tonnes, let's say 150 tonnes at reentry. Starship is 9 m in diameter and 50 m in length, but the nose cone has taper, so lets say that the projected area is equivalent to a 9-by-43 m rectangle. This gives 387 m2. The control surfaces will add to this, so a fudge factor of 1.1 give a final area of 425.7 m2. Starship's (very crudely) estimated mass/area ratio is thus 388 kg/m2. This is higher than the STS, but they're in the same ballpark. Besides, STS was designed with the ability to retrieve a satellite, so I believe that its actual mass/area could go up to something like ~280 kg/m2. Somewhat offsetting this disadvantage is the fact that Starship has the ability to maintain flight at a higher angle of attack, thus the component of area seen by the flow is larger. (That said, while we all know that the AoA tends to 90 deg for the terminal descent, I'm unsure what AoA Starship is supposed to reenter at.)

For reference on frozen orbits. The ~86° one would probably be most convenient for the polar activities of Artemis.

If this is the first controlled flight on Mars, then I take it that EDL was done via a wing and a prayer.

This thread from NSF gives a partial answer; Orion is just big.

I hate to burst your bubble, but there's already a well-established thread for Orion & SLS.

This is something of an oddly-specific request, but here goes. Would anybody happen to have (and be willing to share) some thermodynamic tables? The substance in question is ideal gas combustion products of air and a hydrocarbon fuel (I believe that it would be something like jet A-1). The tables which my propulsion professor provided are from another professor's old Romanian(?) textbook and are not of the greatest quality (and also use the European convention which swaps the roles of decimals and commas). Google has been surprisingly unhelpful in this regard... For illustration, this is what I'm currently working with: And this is more what I'm aiming for (with a different substance, of course). This is from Fundamentals of Engineering Thermodynamics by Moran, Shapiro, Boettner, and Bailey, though the table is cited as originating from J. H. Keenan and J. Kaye, Gas Tables, Wiley, New York, 1945: Edit: Just to be perfectly clear, I'm looking for SI units

Fiber internet has high fixed costs which preclude its installation in rural areas. I actually did an ethical analysis of mega constellations (full text is here) for my engineering ethics course. From a purely act utilitarian view: From a Kantian view: