sevenperforce

My understanding (which may be incorrect) is that spin-stabilization is the primary actor in ensuring attitude control, but the boat-tail helps to damp precession. A Sears-Haack body would be more likely to precess and tumble than a boat-tail.

It's important to distinguish between radioactive decay and fission (something I just clarified in my post above). Decay is when a tiny piece of a nucleus is ejected via quantum tunneling. Fission is when the nucleus splits apart. Decay particles can induce fission. 239Pu does not decay as rapidly as 238Pu, but 239Pu fission produces an average of 2.9 prompt neutrons per event, whereas 238Pu fission produces less than 1 prompt neutron per event.

Another issue, and a reason why boat-tails are favored: you WANT tail drag, to keep the center of pressure behind the center of mass. The small amount of drag you get on the tail is far less than the amount of drag you'd get if you started to tumble. Not to mention the total loss of inertial guidance with trajectory flapping all over the place.

So you can get your terms right (which, let's face it, pop media is NEVER going to manage): Radioactivity. The process by which certain atomic isotopes eject particles to stabilize an unstable nucleus. Radionuclide. An atomic isotope with an unstable nucleus that has a nonzero probability of exhibiting radioactivity. Alpha/nucleon/cluster decay. The case of radioactivity in which certain radionuclides eject neutrons, protons, or clusters of nucleons from their nucleus. Fission. The breakup of an atomic nucleus. Fissionable radionuclide. A radionuclide which can be induced to immediately undergo fission by bombardment with the products of radioactive decay or of other fissions. Prompt neutron. Fission products released immediately, rather than being released with a delay due to decay of other fission products. Fissile radionuclide. A fissionable radionuclide in which any fission event produces an excess of prompt neutrons immediately capable of inducing subsequent fission. Criticality. The state at which the products of each fission event induce exactly one subsequent fission. Subcriticality. The state at which too many of the products of each fission event escape before they can induce at least one subsequent fission. Supercriticality. The state at which the products of each fission event induce more than one subsequent fission, causing a chain reaction. Prompt critical. The point at which a fissile radionuclide reaches criticality or supercriticality with prompt neutrons alone (e.g., a runaway chain reaction has started and there is no way of delaying it, poisoning it, or moderating it). A fissionable radionuclide can undergo criticality, but it cannot undergo prompt criticality. Nuclear reactors can run on fissile radionuclides, fissionable radionuclides, or both. Nuclear fission weapons require fissile radionuclides. Nuclear reactors want controlled supercriticality; they do not want prompt criticality. Nuclear weapons need the fissile material to be prompt-critical. A meltdown happens when supercriticality in a nuclear reactor runs out of control, causing the structural integrity of the fissile mass or its containment to fail. A fizzle happens when prompt-criticality in a nuclear weapon happens too early, blowing the fissile mass apart before any significant portion of it can undergo fission.

Also, note that terminal/wake drag on an engine is a different affair than wake drag on stuff NOT producing a ginormous cloud of hot expanding gas.

That's what I did.

Just paste in the link, and it formats automatically. Mods are allowed in my more recent version.

Assembling a space station in a Lissajous orbit, pretty much. No need for n-body simulation.

I could get behind this. Maybe this could also be an additional use for the gravioli detector. If you have a gravioli detector on your craft and the electricity to run it, then you can find on-rails lagrange points and enter halo orbits.

Very good point.

Um.

Similar to this, but I think yours is better:

Promising challenge! Two questions: how is time measured? Play time or game time? Warp will be a big chunk of the time elapsed. Does warp count? Rule 3 says "you have to return from Kerbin" -- what does that mean? Do the surface samples have to be from different biomes?

Yes, it is. It's fine to discard the drop tanks entirely if you want. Loop The Loop merely requires that some portion of your transfer vehicle remain in Duna orbit during your landing mission, and that same portion ends up in Kerbin orbit. It is intended to encourage the creation of a transfer hab (Stayin' Alive) like an Aldrin Cycler or the Hermes from The Martian while rewarding Apollo-style Orbit Rendezvous missions. You could use a completely expendable transfer injection stage as long as you still bring the Duna Orbiter back to LKO, ready for another mission.

Obligatory: Also obligatory:

@Mesklin You're now at the top of the leaderboard!

I'm gonna run out of likes. How deep did they say the plutonium RTG would get before it melts?

Yeah, bumping up the solid ascent vehicle bonus won't change any current scores but it will make that more competitive. I'll do it.

What are the odds we just unintentionally seeded Saturn's atmosphere with vibrant bacterial life? Not much is going to survive a 75,000 mph impact, but you never know...

Everyone was a bit teary-eyed.

I saw both the DSN antennas go from the combined wave to a smooth wave simultaneously.

Loss of signal. Farewell, Cassini.

Wait, you're right. So the post must have been wrong. 6:31 EDT.

Sure this was the final one? From the Raw Images stream, this was the last one: Nine minutes ago plus thirteen minutes from now is 22 minutes, but the lightspeed delay from Saturn right now is 83 minutes. (looks up PDT) Evidently actual impact was 6:31 Eastern Standard Time. Eastern Daylight Time is not observed in the United States right now.

Doesn't make sense. It said "Cassini plunged into Saturn's atmosphere and disintegrated about 3:31 a.m. PDT (7:31 a.m. EDT) on Sept. 15, 2017." 7:31 EDT was nine minutes ago, but it currently says "mission end" in 14 minutes. Maybe it's an EDT/EST mixup? F.