sevenperforce

So 105.7 tonnes total S2 propellant. Interesting. I have typically been using SLR's estimate of 111.5 tonnes S2 prop loading in most analyses/simulations. Slight change for high-energy orbits, I think. What page are you seeing that data on? Table 2-1 on p10 says 1,135,925 lbm of total F9B5 propellant, or 515.25 tonnes, though it says there is less propellant usage for some missions. This corresponds to 409.55 tonnes S1 propellant.

Think they'll do a static fire before they attach the nose cone? Or are they transporting it in piecemeal for assembly at the launch site?

Lots of people use sepratrons to stage off parallel stages, so if you chuted at staging you'd have that effect as well. I could get behind that. Pretty simple to implement, too.

There are tons of reasons you might want to do that. Stage off your heat shield when you pop your drogues Fire retrorockets and pop a chute simultaneously at spaceplane touchdown on a short runway Place drogue chutes on a decoupler so they can be staged off when the mains are popped Chute down parallel stages for recovery without requiring a probe core Pop chutes and fairing simultaneously Fire solid retrorockets and pop chutes at the same time for a high-altitude, low-opening (HALO) descent

Nope, you can't push off a vacuum. You can push off of a local electromagnetic field, though.

As I explained, you can use celerity (proper velocity) rather than standard velocity to get meaningful Lorentz terms for multiples of c.

I know, right? As morbid as it was, I couldn't help it. Check yo damn staging.

Thanks Vandy. In other news, the plot thickens: the cult leader published an op-ed whining about the documentary, and I responded: https://medium.com/@davidstarlingm/the-arks-false-profit-3131ab78fbf6

If you're that low to the ground then definitely go with an airbreathing engine every time. A turborocket with a reversible intake is ideal.

Speeds in excess of c have no physical meaning, but celerity in excess of c is meaningful. So I calculated based on celerity. Celerity is speed as the distance in the rest frame divided by the time elapsed in the moving frame.

Those jigs. I love seeing those jigs.

Propane obviously. Wasn't sure about the oxidizer, though.

Six engines on the first stage, one on the second stage. They are claiming a TWR of over 400 on the 3D-printed engines which seems ungodly. I'm presuming this is a propalox rocket but we're not really told.

Uhh... this doesn't quite make sense to me. Its density is 22.59 g/cm3, or 22 590 kg/m3. A five meter sphere of osmium would have a volume of 65.4 m3 and weigh almost 1500 tons. Assuming you input that wrong number in your calculations, your already pretty spectacular estimates are too low by a factor of almost 150. Yikes...looking back, I actually messed it up in two places. I initially overestimated because when I asked Wolfram to give me the volume of a 5-meter-diameter sphere it dropped "diameter" which gave me 524 cubic meters. 524 cubic meters of osmium would mass 11,830 tonnes, not 11.83 tonnes, so I messed up again. But yes, the correct value is going to be 1,479 metric tonnes. Plugging in the numbers from before, that gives a relativistic kinetic energy of 1.994e39 Joules. The relativistic mass of the object would be roughly the same as the mass of the large asteroid Juno. If all its energy was deposited into the Earth at impact, it would not only obliterate the Earth, but accelerate every particle of Earth in every direction at 8.6% of the speed of light. The explosion of Earth would be so energetic that the expanding cloud of relativistic plasma would be energetic enough to obliterate the moon, Mars, and Venus. At the distance of Jupiter, the shockwave would hit the gas giant with a total flux of 4.9e32 Joules...not enough to blow it up, but enough to rip away the majority of its volume (though only a small fraction of its total mass). I was going back of the envelope, so YMMV, but I am fairly sure that the interaction cross-section simply will not be great enough if you have that much length contraction. See the ladder paradox for more info.

Great! Let me know what you think.

If we use "15 quadrillion times the speed of light" as a measure of celerity rather than speed, we can do a little more work. As I explained above, length contraction would shrink the Earth to the thickness of a strand of DNA, making interaction unlikely. However, let's handwave that part. The original post doesn't specify mass for the object, but in any question of penetration, the most "indestructible" object will always be the object with the greatest density. Osmium is the densest naturally-occurring mineral, so I'll go with that. A five meter sphere of osmium would mass 11.83 metric tonnes. A Lorentz factor of ~15e16 can be used with the standard equations to determine the relativistic kinetic energy K of the impactor: K = (γ - 1)*m*c2. The kinetic energy of our impactor is going to be a nice charming 1.595e37 Joules. To put it in perspective, as much energy as the sun produces in 10,667 years. It is enough energy to obliterate 100,000 Earths.

Common misconception -- relativistic energy alone cannot create a black hole. Obligatory "nothing can go faster than light", etc etc. However, you can represent speeds greater than c by measuring celerity (w) rather than velocity (v). Velocity is the distance per unit time as measured by an observer, while celerity is distance as measured by an observer per unit of time as measured by the object. There is no upper limit to celerity. "15 quadrillion times the speed of light makes no sense" (it is like saying "a vacuum with 15 times more suction than empty space") but 15 quadrillion c does make sense as a measure of celerity. For celerity many times greater than c, the Lorentz factor γ is approximately equal to the celerity given in multiples of c. So an object with 15 quadrillion w/c has a Lorentz factor of 15 quadrillion, which means its relativistic mass is 15 quadrillion times greater than it would otherwise be. However, it impacts other things as well. That 10 meter ball will undergo length contraction by a factor of 15 quadrillion, making it approximately the thickness of a single proton as viewed by an Earth observer. From the perspective of the ball, Earth will have shrunk to a disc only 0.8 nanometers thick, slightly smaller than a strand of DNA. The ball would pass through Earth without interacting.

Any updates on the failed landing?

I grew up talking to him, haha. I'm the black sheep who betrayed AiG and joined the dark side. Looks like it is currently available here though I don't know how long or whether your viewing location matters: https://www.pbs.org/video/we-believe-in-dinosaurs-hnhjlz/

Ken Ham liketh me not at all.

You should be able to watch it streaming live on the PBS website. If not you can watch it for a small fee on Amazon Prime Video or Google Play. Update: the leader of the anti-science cult central to the film speaks out in criticism of me and the filmmakers: https://www.courier-journal.com/story/news/religion/2020/02/17/kentucky-ark-encounter-documentary-what-you-need-know/4773758002/

NASA's Heather Archuletta tweeted a long thread yesterday about why anyone at all who cares about science absolutely has to watch We Believe In Dinosaurs when it airs tonight at 10 Eastern on PBS. The film follows, among other things, my own personal journey out of the anti-science movement. I encourage everyone to watch and comment. Obligatory from xkcd:

I think that's broadly the best plan. One of the reasons for placing LOP-G in NRO was this exactly. Assuming a polar surface mission, NRO is the best abort destination at almost any point. The only better destination for abort during descent is a frozen low polar orbit, but since Orion has no chance of hitting LLO and getting back to Earth entry interface, it was out of the question. If you're on the surface at either pole, you can abort to NRO at literally any moment. Some phasing is better than others in terms of dV margins, but it's all pretty close. I am fairly sure that you can abort during descent at any time too without phasing issues.

That was my thought. Grab an existing second stage, mod it slightly, and slap it on top of your preferred launch vehicle. The upcoming M10-based cryogenic stage for Vega-E would be a methalox option. You could also use a mildly modified DCSS or Centaur. Heck, you could even put a cluster of Electron upper stages into play, if desired.

Doesn't even have to be ACES. Can be any cryo stage with multiple restarts, a docking ring, pointing support, and at least 3-4 days of loiter.