wumpus

I think SSME nozzles are designed for vacuum flight with a "spoiler" that prevents overexpanding from being too much of a problem. Since for the first five minutes or so the Solid Rocket Boosters provide about 4/5ths of the thrust, you don't have to worry much about the SSME nozzle being efficient/providing maximum thrust at sea level.

Launch a SLS in 2020, launch a crewed SLS in 2022, launch a block 1B in 2028? I have to wonder what the SLS Senators think of this. Is the embarrassment of failure and delays worth adding even more pork to their pet project? I'm guessing that's part of the job description for senator, so yes. There is little indication that the CLV* (cargo launch vehicle) is going to be a Falcon Heavy (presumably for political reasons). Are they still developing this along with the SLS? Or do they just put it out for bid for the usual NASA shenanigans. * The only acronym I could find for CLV was "crew launch vehicle", originally Ares I, and a "CaLV" (cargo launch vehicle) as Ares V. This was later canceled and reborn as SLS.

A de Laval nozzle will be more efficient for at least a single pressure (such as vacuum) than an aerospike. I'd be curious just how high an altitude you need for a de Laval nozzle to be more efficient for the entire flight (from that altitude to vacuum). This is mostly an argument against SSTO aerospikes (SSTO is a bad idea [at least for Isp<500s] and aerospikes can't fix this), but isn't for first stage aerospikes.

I suspect the key would be to make sure that the preburner needs liquid propellant to operate. If it pulls pure He, you are ok. If it pulls a mixture of He and propellant vapor, while it might not have remotely the torque on the turbopump the lack of resistance would still make it overspin. This might be a significant advantage for Rocket Labs as being able to eke the last bit of fuel out of the final stage should help a bit with the rocket equation (those last drops of fuel give exponentially more delta-v). I wouldn't be surprised if they managed to use all their fuel (or pressure fed, but they typically don't have the Isp of pumps).

Except that it won't start pulling air. It is far more likely to start pulling helium (or other "filler" gas), which presumably wouldn't compress the same and probably wouldn't pull at the right velocity and could presumably still overspeed. Of course, this assumes that there is enough propellant (whichever one) being pulled to power the turbopumps. Most turbopumps (exceptions include expander types (RL-10), electric (Rutherford engine), and old fashioned hydrogen peroxide (V-2)) use the same fuel contained in the propellant, so they will quickly stop being driven when the fuel runs out. If you overspeed before there isn't enough fuel to drive the propellant, your turbine still flies apart, tearing lots of holes in the middle of a formerly controlled explosion. If you don't, then it just stops spinning.

For suborbital spaceplanes we have the X-15. 199 flights (I'm sure plenty were test flights and with the early engines that couldn't reach space. And almost all of them didn't go into space but simply went fast horizontally, which is probably harder on the spacecraft than a parabolic spaceflight). I think this says more in just how much easier it is to go suborbital rather than orbital than the ease of turning around spacecraft. The number of assumptions made in planning on running while still learning to crawl is amazing. Elon Musk has mentioned that propellant cost for his rockets simply isn't a concern (although he probably does like how cheap methane is), especially considering that they are busy trying to recover a fairing (and hopefully relaunching one more or less as I type this) that costs roughly 30 times the total propellant cost. While assembling a multistage rocket does require skilled technicians, there is absolutely no reason to assume that mating a Skylon to some sort of carrier aircraft (which could take off/land on a Concorde or A380 runway). Also you have all the fun of working with hydrogen (which may or may not be common by the time Skylon might ever fly).

This thread needs more Orion. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20000096503.pdf (no idea why the pdf is so bad on an allegedly 2000 paper (that references at least one other 2000 paper). http://www.projectrho.com/public_html/rocket/enginelist.php https://www.amazon.com/Project-Orion-Story-Atomic-Spaceship/dp/0805059857 Orion was beyond kerbal. It was basically E.E. doc Smith level rocketry that could be built with 1960s tech (quite possibly easier than now, you could probably find welders familiar with welding battleships together during the 1960s. That's a skill that would come in handy in building an Orion).

The US Navy fielded the Talos ramjet missile from 1958-1979. Going to air-augmentation should be seen as a step backward for missiles. Missiles should be able to fly at fairly specific velocities, although air-to-air pretty much means completely uncontrolled altitudes. But the Talos was surface-to-air, so presumably could operate anywhere a MiG could. This is mostly a different problem than maximizing delta-v while getting out of the atmosphere, but hopefully ULA will someday hire someone who worked on one of these. One thing to remember about any fuel-efficiency ideas: the fuel (and oxidizer) in a falcon 9 is said to be ~$200k. The fairing is $6M. Expect Mr. Stevens to spend a great deal more time trying to catch a fairing (whether or not it will be eventually required) than any attempt to apply air-augmented shrouds on a rocket for cost efficiency reasons (although I'd assume that reducing the size of the booster wouldn't hurt overall costs).

Magnetic media has resolved tighter than optical (blue lasers at least) can resolve. I doubt you will be focusing UV very well (the semi conductor industry has been dragging their legs going from normal optical to uv for years. Expect any company that can't make the transition in the next year or so to drop out of the race for producing "bleeding edge chips"*) and I've never heard of an x-ray lens being big enough to be functional (perhaps mirrors will work). In any even, modern NAND flash approaches optical resolution limits (for cost reasons, modern CPUs push into "really weird optical tricks") and then stack the transistors 48-96 layers deep. You aren't getting a tape to do that, unless you go 3D (holographic tape might work, but still won't touch the density. The holograms would effectively act as a ECC/frequency expanding trick). The entire problem assumed humans would be on board. And remember when I mentioned that optical media used half the bits to correct the other data bits? You would have to do that with DNA as well, but obviously not as much. In other news I'd like my own DNA re-encoded with these tricks so it can "scrub" out any transcription errors and mutations (but not with today's technology. It will have to wait).

There is a bit of slight of hand going on: they talk a lot about mach >5 but only show plans for mach 2.2. Mach 2.2 is *possible*, but still probably involves at least a billion dollar NRE (possibly only hundreds of millions since they have SpaceX alumni used to doing things on the cheap). Looks like a plan to scam VCs out of money, possibly to play "not so simple airplanes" in real life. Going to mach ~5 would simply eat any possible profit (don't count on any) from the mach 2.2 plane and require amazing levels of both research and development. I've been pushing the X-43 as a great example of this, but it has almost no payload and I have doubts about the range (room for all the hydrogen fuel it needs). Also don't forget about the time needed to go to the airport (that can launch/land mach 5 aircraft) and from the airport you land at: if the customer isn't taking two helicopter flights already for an all-air flight you won't save any time with this ridiculous aircraft. You probably won't find any customers for the mach 2.2 aircraft that aren't heavy helicopter users either.

A good bomb is one that doesn't blow up during storage/transportation/waiting for use (there is one lost in a Carolina swamp that is said to have only managed this trick by luck). Anything else is gravy.

From what I understand, multiple layers of very thin films a long way from the ship are fairly effective, although mostly researched as "navigation shields" in Star Trek lingo (shields to protect you from the dangers of flying through space, not withstanding enemy attack). They are great for high speed physical strikes (such as nano-asteroids) and may function as "dune shields" limiting torpedoes to speeds that won't vaporize them on contact. Pretty much any space warfare centered around sustained beam fire means that maintaining more than 1 flanking attack (because using three dimensions allows you to angle the surfaces of your heatsink perpendicular to attackers from two directions) means victory. While the ISS's radiators might be significantly smaller than the solar arrays (and of course it is typically shown to see the solar arrays, so you don't often see the radiators that have to be perpendicular to the solar panels), they do take up a lot of room. And even in "E.E. Doc Smith" type space opera (think Star Wars or Star Trek, only limited to real physics*) those radiators have to be within orders of magnitude of size *per* *Watt* of the ISS. So if you are blasting spaceship-destroying lasers willy-nilly, you are going to need either open cooling (with similar issues to the rocket equation as you keep pumping out coolant) or closed cooling with all radiator issues (and vulnerabilities) that implies. My previous calculations (probably inspired and posted by some other Matterbeam post) included below. * E.E. "Doc" Smith's physics might be seem a little iffy, but seeing how he wrote his famous works in the 1920s-1930s I'll cut him that slack.

I really doubt that anyone will be interested in the raw data (except those interested in developing such systems, but I suspect they will have to go to the site for such data), the point is to process the array to mimic a single radio telescope. This cuts down the data needed by a factor of a quarter of a million, and the "denoising" effects by merely averaging those individual telescopes would be significant (and I expect significantly more sophisticated telescopic tricks plus more well known DSP filtering as well). But that still means that you are getting upwards of 160 Gb/s of highly useful data. Better start hoarding LTO tape. Modern storage devices use a great deal of their bits for error correcting (and detection). CDs and DVDs have 1 bit of ECC for each data bit. I've heard that hard drives wouldn't work at all without nearly all their error correction bits (but don't expect to find out how many are needed/on the drive). So I'd expect that with enough ECC (and hints of where the data goes. Think of the ancient trick of numbering your Hollerith deck) you could get DNA storage to fit: just that I doubt that anyone expects a CRISPR unit to be cost effective storing data.

If not, they'd almost certainly be using Falcon Heavy. I wonder just how much pressure the satellite design teams had to make a compact satellite (low mass wasn't the issue you'd normally think).

Dr. Salk seemed* to insist that he was only one of a large team of researchers that developed the vaccine. A similar story more familiar to this board was that it took something like 50,000 people to design, build, and launch the Saturn V but we mostly remember Neil Armstrong. While people want a single hero (if anything it makes sculpting a statue easier), don't forget the rest of the team. * mostly taken from a [temporary] Smithsonian exhibit. I think they need to put it back up until the whole antivax movement goes away. I'm not that familiar with the process of developing the vaccine, but probably should be.

I remember a rant (I think it was on the Van's Aircraft website) that insisted that the airspeed indicator was "the gauge that lies". Perhaps you simply have too realistic a device. - The rant was why you shouldn't put too much engine in your homebuilt aircraft. When they say "don't exceed this velocity", they mean it and you shouldn't trust the airspeed indicator to indicate safety.

Judging by what the uncool kids over at https://www.reddit.com/r/DataHoarder/ have to say, (on a good sale*) retail hard drives make it hard to justify tape. Tape might still be surviving in "enterprise grade disk" vs. "enterprise grade tape" (*all* tape these days are for servers. Hard drives appear to be heading for either for servers or the cheapest computers, and I expect the cheapest computers will simply switch to even less flash), but it is getting close. Flash vs. hard drive seems to have a factor of 5 difference in cost, but that is coming down quickly. I wouldn't be surprised if the first manned flight to Mars wouldn't have this question: flash will have won outright (or be replaced with something more high tech). Apparently Google is already storing exabytes of data (I expect their answer would be "x% of a datacenter" if they were talking. They aren't.) * this involves waiting for a holiday sale at Best Buy and buying the 10TB WD external drives and removing ["shucking"] the hard drive (USA only). Gets to be around $16/TB. LTO-6 tape is on Amazon for less than $10/TB, but good luck finding a cheap price on a LTO-6 drive.

Nervas simply don't have the disastrous failure modes that flourine has. I'd go so far to say that they are far safer than a first stage hypergolic. Nervas can't explode, their fuel tanks can't explode (see Apollo 13), the only real danger is overheating and meltdown (and possible extra radiation during such an event). I wouldn't recommend lighting one at less than Earth escape velocity (at least until they are proven reliable), but even doing that should be more or less safe (I'd expect it to be possible to set it so "99% of all possible failures to reach escape velocity drop the fuel rods into the Pacific"). Your real issues would be largely about proliferation, and it would take roughly the resources of a nation state (far more than ISIL at its peak) to begin to obtain weapons grade nuclear material from a nerva. Scott Manley (of course) had an interesting series that included roughly the steps needed to go from there to weapons: they were looooong. I'd expect a diplomatic solution long before any nerva could be converted into something else. Another thing I recall about KSC's location (Kennedy, not Kerbin) is that there exists an orbit from there that is almost entirely over ocean. Since learning about real rocketry (and why you want the lowest inclination your latitude will allow) I've nearly forgotten about it, but it might be useful for something like this (then again, nervas are pretty slow. Maybe you can angle a bit to avoid the precession thanks to Earth orbiting beneath you and maintain that exact orbit).

the tech that would help push on the development of the future pluto spacecraft How would humans survive You've pretty much posted the tech needed for such a thing. Ion thrusters powered by nuclear energy. Gravity assists are always a good idea as well. Humans aren't coming along, that just is ridiculous (at least until people are being born on permanent Mars colonies or similar). The journey out is years and trying to leave via ion thrusters would take forever (just to get back to Jupiter for your trip home). While you won't have to deal with the rocket equation (lots of delta-v needed to get back) the mass of the life support and habitation units would be far to much for the wimpy ion thrusters to accelerate at all. If you want to force humans along, you have pretty much the same problems as going to Mars, only much, much worse. I'd recommend (for either "planet") sticking refilling stations in one or more elliptical orbits to leave Earth (and at least on the target "planet" for the return flight), all delivered via ions or similar. The humans would then use a spacecraft powered by chemicals (at least to escape velocity) by "Pe kicking" (aka the Mangalyaan maneuver) by docking with the successive refilling stations (at Ap) and burning at Pe. Expect to still use ions (or perhaps some slightly more powerful thruster) past Jupiter and to capture. I think this is a good plan for Mars, a silly plan for Pluto.

Try here: https://en.wikipedia.org/wiki/Kepler's_laws_of_planetary_motion for a more graphically based concept (Kepler had to work with geometry). Note that for circular orbits you can derive Newton's law of gravitation with algebra, dealing with elliptical orbits appears to want a pair of partial differential equations (which meant that inventing calculus gave Newton a huge leg up on discovering the law of gravitation).

I think the pace of the game works well with Kerbin (low orbital velocity plus heavy fuel tanks). I'd also have to assume that throwing newbies into RSS/RO would pretty much kill the game (throwing them into "don't worry, it's just rocket science" is bad enough). I'm glad that RSS/RO exists (and eventually expect to get around to completing the "normal/modded" game enough to switch to RSS/RO). EDIT: the "textures" issue baffles me, but presumably because I was playing early enough that textures aren't going to change my style. It reminds me of the "bring back the barn" thread where those attacking the aesthetics of the barn (and related buildings) texture's were talking past the people who wanted a barn (with or without the "broken" textures).

As far as I know, the Soviet Gnom program (an ICBM) was the only attempt to make an air augmented rocket and was canceled in 1965 before flight tests. While the rocket may spend little time in the atmosphere, expect it to consume 1/2 to 3/4 of the fuel while doing so. Changing the Isp of the rocket from kerolox level Isp to hydrolox level Isp should have some cost advantages, but don't appear to be enough to overcome the issues of designing the aero intakes to handle the wildly varying situations. Unfortunately the air-augmented rocket's Isp is more like 400-500 (and anything not using RS-25 based engines is well under 400 during atmospheric flight) which means that you don't get the huge benefits of Ramjets and similar (of course it should be significantly easier to design and manufacture). The idea is simply to heat the atmospheric air and use it as a propulsion medium rather than just the water and carbon dioxide reaction products.

There have been whispers of the Russians thinking about disconnecting their bits and going home (presumably burning up in the atmosphere). You never know, perhaps they might sell their part of the station to the Chinese...

One thing you never did was show how much momentum per Watt you get out of a photon, and compared that to an ion being flung into space. You need a unbelievably efficient process to begin to make sense. Why a laser? It seems that ordinary luminescence would be more efficient. You don't need to focus the light all that well, just enough to get going in the right direction. Is a laser needed to handle the concentration of energy in space? I understand most of the research was for lasers, but that doesn't mean that they make the best means for an engine. Blackbody radiation will be used regardless of the interstellar propulsion method. Also expect to eventually align your radiators perpendicular as speeds go relativistic (presumably half pointing each way) to travel, just to avoid the constant high-energy bombardment from interstellar hydrogen hitting your radiators.

Cognitive changes: The US Navy is unlikely to publish data for similar results on board submarines. I wonder what the results for Antarctic base (especially over the N. hemisphere's summer) are.