sevenperforce

That sounds pretty likely.

But whyyyyyyyyyy

Technically any rocket stage is a "liquid rocket booster"; do you mean "no radial staging of the launch vehicle"?

Can you add points to these two, err, points? I notice there are no constraints on the launch vehicle....

Limiting factor on the muzzle velocity of a normal combustion gun is the pressure wave pushing the projectile up the barrel. In a gun, the highest pressure and acceleration are at the very moment of combustion; both drop immediately.

As one of the resident physics people around here...I agree with @p1t1o! Let's hear it! What's the worst that can happen -- we all learn more science?

Well I fudged that up nicely. Took the square root of 31.04 rather than the square root of 1031.04. The square root of 1031.04 is roughly 3x1015. And 3x1015 AU is 51% of the radius of the observable universe. So the answer is: all of them. We would hear all the supernovas in the observable universe. Pop. Pop. Pop. BANG. Pop. Pop. Whisper. A salted bomb is, as I understand it, a thermonuclear device in which the tamper is "salted" with isotopes specifically intended to maximize fallout, rather than yield. A dirty fusion bomb is a bomb where the tamper is made with isotopes intended to maximize yield. A hydrogen bomb with a lead tamper is "clean", a hydrogen bomb with a uranium tamper is "dirty", and a hydrogen bomb with a cobalt-salted tamper is "salted".

https://www.quora.com/If-you-could-hear-a-supernova-explosion-how-loud-would-it-be A supernova at 1 AU would be about 314.4 decibels, based on energy output. The human hearing threshold is about 4 decibels. 314.4 decibels represents 1031.04 times more energy than 4 decibels. Because a sound wave loses power with the square of the distance, this means a supernova would need to be 5.57 AU away before it would drop to the human hearing threshold.

Yeah, I was thinking in terms of the old usage. RDD is actually not that deadly, all things considered. Has more value as a weapon of mass chaos than actual mass destruction. Most more-available dangerous radionuclides are very short-lived. You need a reactor or a nuke to get the stuff that's both deadly and long-lived.

The technical name for that is a "radiological dispersal device". However, upon review, it looks like "dirty bomb" is used interchangeably between RDDs and high-fallout thermonuclear devices.

Strictly speaking, a "thermonuclear device" refers to a fission-triggered fusion bomb, in which the heat ("thermo-") from a fission device is used to initiate a separate nuclear fusion reaction. The other options are fusion-boosted fission devices (fission weapons with a small amount of fusion fuel to increase yield), fission devices (fission-only bombs), and chemical-munitions radiological weapons (radiological dispersal devices using conventional explosive to disperse radioactive isotopes). There are a few other common terms, too. A "dirty bomb" typically refers to a thermonuclear device with a high amount of fissionable material in the tamper, resulting in large amounts of fallout. A "clean bomb" typically refers to a thermonuclear device with little or no fissionable material in the tamper, such that the majority of the energy comes from fusion. A "neutron bomb" is typically a small thermonuclear device designed to maximize neutron flux and thus improve kill rates against blast-hardened targets.

Well, the defining difference between an RTG and a nuclear fission reactor is whether the heat comes from steady-state decay or from induced criticality. The SAFE-400 nuclear fission reactor used uranium-nitride fuel with rhenium neutron moderator rods and could be turned off and on at will. Rather than the thermocouple used by most RTGs, it used a helium-xenon closed gas coolant loop via Brayton cycle. Nothing about that is "fancy RTG". SAFE-400 was about 2 feet tall and about 1 foot in diameter. Of course, it massed half a tonne. SNAP-10A, launched into space by the US in 1965, used thermocouples for the electrical energy conversion, but the nuclear reactor itself was a uranium-zirconium-hydride core with beryllium neutron reflectors for criticality control. I'd argue this is still a fission reactor even though it used thermocouples instead of a coolant loop. I've formerly speculated that a very very small nuke could be built by using neutron poison rods to keep a critical mass subcritical until detonation. EDIT: SNAP-2 was built to be paired with a liquid-mercury Rankine cycle power loop and it was nearly as small as SAFE-400.

Well, it WAS carrying a Dragon capsule. Which was lost because there was no contingency for chute deployment after an inflight RUD. If it had been a Dragon 2 with human occupants, then the abort engines would have been fired and they would have survived anyway. If a person had been strapped inside the Dragon 1 pressure vessel of the CRS-7 mission, and if it had been programmed to deploy chutes after an inflight RUD, then yes, the occupants likely would have survived. Though they would have thereafter died of CO2 poisoning while waiting to be freed from the floating capsule.

The various fission reactors built for satellites and spacecraft were much smaller. https://en.wikipedia.org/wiki/Nuclear_power_in_space#Fission_systems

Yeah, unless they start shipping gold bars to the ISS, CRS payloads via Dragon are more volume-limited than mass-limited. There are few realistic CRS payloads which would be small enough to fit on Dragon yet heavy enough that Falcon 9 couldn't send them up with an ASDS recovery.

Nothing under CRS missions, anyway. FH could easily put a whole new module the size of Zvezda up, though attaching the thing might prove tricky. Of course nothing like that is planned for ISS.

The N1 fired thirty engines on its first stage at launch, and we all know how that worked out. There are a lot of launchers with multiple engines plus various verniers, but that doesn't really count because the verniers are much smaller. I do not know of any orbital vehicle which uses more than nine identical boost engines on the first stage. Engine start is risky because you're dealing with potential oscillations, thrust differentials, and force interactions which could conceivably produce cumulative effects which would not be anticipated. It will be much worse than Delta IV Heavy in flight.

And microsat launchers can always just slap on a COTS SRB for extra dV.

Nuclear stealth subs can camp out just off the coast, surface and fire nukes, and sink again in a matter of minutes. The target gets no warning whatsoever because the dV and flight time is so low. The air-augmentation advantage for air-launch would be if you can get an orbital launcher small enough that you could load several of them into a conventional heavy bomber with no major changes to the aircraft itself. It definitely has all the benefits of SABRE with less cost. In fact, if you took a vehicle half the size of Skylon, filled it up with kerolox, and slapped a pair of Merlins on it with air augmentation shrouds, it could basically do everything Skylon can do. The shrouds even double as altitude-compensation nozzles. But like I said, it doesn't scale well at all. The length of the shroud is a function of the diameter of the shroud, so mass growth gets pretty bad pretty quick.

No real need for it. The GNOM was intended to minimize the size of a heavy-payload ICBM so it could fit on a mobile launcher and thus preserve retaliation ability after a US nuclear first strike. It was something like half the size of its conventional counterpart, so it worked really well for that. The US never developed one of these because its nuclear-armed subs were even more invulnerable to a Soviet first strike and could get away with a smaller launcher by virtue of proximity. After the end of the Cold War there obviously was no more concern about minimizing the physical size of ICBMs because there was no imminent threat. For orbital aspirations, the niche for a ducted rocket is hard to find. The in-atmosphere acceleration phase of an orbital booster is much shorter and you push out of the thick lower air very fast, so the advantage of air augmentation is more limited. You'd want to shed the shroud as soon as it was no longer useful, but that means a VERY early staging event (the Falcon 9 isn't even halfway through the first-stage burn before it clears the useful portion of the atmosphere, and it's already dV-weighted toward the upper stage). Plus, a shroud scales poorly with vehicle size, making it ill-suited for larger launch vehicles. In most cases, it's far cheaper to simply make your rocket a little bigger than it is to design an air augmentation shroud, especially for expendables. One potential use for air augmentation might be improved air-launch. With air-launch, you definitely want your rocket to be as small as possible for the sake of your carrier plane, so cutting down on mass and size with a shroud is useful. Plus, you're already moving horizontally with significant airspeed at launch, so you get more benefit out of your shroud, and you can design it for a much smaller range of air pressures and densities.

The GNOM was a fantastic little cruise missile that vastly outperformed its conventional counterparts but didn't enter service because of USSR politics. Turbojets don't make much sense for orbital flight; air augmentation does. One of my pet designs is a stage-and-a-half SSTO similar to the Saturn 1-D concept, where you have a single tank feeding a single engine plus multiple engines on a jettisonable skirt. The skirt can be designed with an air-augmentation bypass without mass penalty, boosting efficiency during the initial climb. Laythe has oxygen, so any jet engine will work there. But the nice thing about an air-augmentation approach is that you don't actually have to have oxygen. Atmospheric gas goes into the intake, is heated and expanded by mixing with the exhaust, and boosts thrust "for free", at least, when you're going at less than Mach 3 or 4. Up around Mach 5 you're going so fast that it's hard to speed up the airflow any more than your airspeed. No need for combustion. If your atmosphere does have oxygen, you can always boost your efficiency a bit by running your engine fuel-rich so the oxygen has something to reheat with, but the gains are low. I would love to see a "boost duct" part in KSP that would allow you to combine any rocket engine with any intake to boost efficiency in this way without requiring an oxygen atmosphere.

Longer-range A2A missiles intended for targets out of sight line are sometimes air-augmented, like the Meteor.

Yes, absolutely. They are great. They have already flown, actually...though not as orbital rocket boosters. Rather, they are used for the acceleration stage of air-to-air missiles, because their low weight and high thrust/efficiency make them good for strapping to the underside of an airplane. However, the added cost and complexity doesn't make them as useful for orbital boosters. Why add a few extra tons of metal and an expensively-developed inlet geometry when you can just make your strap-on booster a little bit bigger, or add another one altogether?

Deployed! That's a wrap. Congrats SpaceX!

Lots of ice forms on the upper stage; when the engine shuts down, the jolt shakes a bunch of it free, sending specks of ice in all directions.