sevenperforce

So I don't know how many of you have been watching the live feed of the Falcon 9 stage 1 recovery at Port Canaveral, but I have been following it pretty closely. It seems like a really long process, probably because this is the first time pulling it off the barge and they are taking their time to carefully document everything as they go. When they brought it in, the stage was clamped down to a series of concrete blocks at the base, with the landing legs held in place by welded shoes. They brought in a crane, attached it to the interstage, removed the shoes and base clamps, and brought the entire booster off the ship and onto the dock. They buffed the weld spots off of the ship pretty quickly. Once the booster was attached to the crane, the legs no longer bore any of the weight. The crane lowered it onto four platforms and 8 workers manually pushed the base into alignment so that launch clamps could be fixed to it. The legs have remained deployed. They kept the crane fixed to the top, presumably to avoid sway. There was a lot of inspection of the legs and the general outer body. They attached an electrical line at one point, and they have a large hose running up one side to the top of the booster. I do not know what it is for; they might be draining some additional or residual fluids, or they may plan to use that line to repressurise the landing legs. They brought a truck carrying white gas tanks up to the base a little earlier today. Last I saw, they were catching guy wires to the top of the booster. I am not sure why. I doubt they will detach the crane attachment, simply because I think they will need it to lower the booster to a horizontal position. I am guessing that we will see the landing legs retracted pretty soon.

One thing that is excusable but ultimately pretty unrealistic is that alien species end up having two equal sexes. Human beings, with equal male/female birth ratios and relatively similar body plans, are the exception on Earth already. Granted, there are plenty of scifi worlds where this is not the case, but it usually is (especially in more recent pop scifi). As far as vacuums are concerned: holding your breath is probably the best way to get massive immediate observable damage during a decompression event. Otherwise the chances of physical trauma anywhere other than your face is quite low.

...is the retcon.

Can you do it with landing legs?

A few thoughts.... Keep them small. Large sea creatures are really not going to make it into space. I'm thinking small octopus size. Give them the ability to create their own structures. Numerous soft-bodied crustaceans and invertebrates already produce their own shells, so it stands to reason that sentient versions of these creatures could evolve the ability to control this process and "grow" objects. We need air to breathe; aquatic creatures don't necessarily need water to breathe. Some can get away with a moist environment and respirate through their skin.

Y'all should check out the Canaveral port live cam....

No, not up to orbital speed; up toward orbital speed. A nuclear thermal ramjet is limited to lower cruise velocities. Launch vehicles have to be optimized for acceleration rather than cruise.

Eh, there is no way to dump that much heat that quickly. You've got to just go ahead and accept the coolant losses if you want a SABRE-style precooler to work. Project Pluto got around this by using SRBs for launch and having a fairly low velocity, but a launch vehicle needs to be able to accelerate well up toward orbital speed.

The precooler would still drink a considerable amount of liquid hydrogen...just saying.

I can forgive that if and only if the engines depicted are "warp" engines or otherwise actuate FTL travel, as it is conceivable that something like an Alcubierre drive would need constant power to be engaged and would grind to a halt if the engines stopped. My biggest pet peeve is possibly in depictions of the Earth-moon system. The moon is not in low earth orbit. Also it is quite large. Somehow everyone seems to mix that up. Another offender, of course, is when technobabble is used that COULD mean something but doesn't. How hard is it to find a nerd and figure out that watts are a unit of power, not energy (or, worse, force or torque)?

And by "nuclear powered skylon" I assume you mean "not skylon at all, but a HTHL spaceplane powered by a hydrogen-precooled supercharged nuclear thermal turborocket"?

Launches aren't sold based on weight, typically. The Falcon 9 is quite overpowered for LEO due to the really fantastic T/W ratio of the Merlin 1Ds; it was designed that way to give it a margin for reuse.

Well, sorry. But I was talking about more than just agriculture because I think that's too narrow a restriction. And when you talk about arable land requirements, it's more than just direct food consumption. There is land which used for energy or consumable production which would otherwise be used for food, land which is used for food for the workers who produce goods and services, and so forth. The linked study looked at total carbon footprint and used land area to represent it.

Popsci wasn't the origin, just a report point. Here's the original, and here's a BBC news source discussing the limitations and extensions of the figure. And why would I limit it to agriculture? I already said it was based on overall standard of living.

Still not enough. My memory was correct; it was actually 4.1 Earths.

To some degree. However, it would probably be easier to terraform more of Earth to make it arable than it would be to terraform other worlds. Not that I don't want us to, mind you.

Right. Population density is not an issue, but it would require something like four Earths worth of nothing but arable land to provide an average standard of living comparable to that of the American low middle class.

Yes, your English is entirely fine; you just seemed like you were being intentionally difficult. I could be wrong...hence the questionmark.

Trolling?

As am I. Anyone want to take a whack at the propulsive-landing version?

So? Asteroids can have natural satellites, but there are no asteroids with moons -- at least, not as I have defined "moon" above. By defining "moon" as a gravitationally-rounded natural satellite, the definition of "planet" becomes much simpler.

No, can't make enough.

As others have said, aerospace-grade propellants are already usually pretty nasty stuff, so this comes with the territory. Granted, there are certain things which exceed even rocket scientists' love for delta-v, like pentaborane, but neither HTP nor hydrazine are nearly that bad. Hydrazine is fairly stable in the absence of a catalyst or ignition source; it's just quite toxic. HTP is stable enough if stored correctly and you won't be dipping anything into the tank. Yeah, the whole concept (at least as provided in the OP) was pretty much dead in the water as soon as I realized that my energy calculations were totally hacked due to improperly stacking exhaust velocities. The simplest air-augmentation setup is to wrap a simple shroud around the exhaust nozzle, which can increase thrust by up to 15% at launch due to pure ejector effect and will ramp up considerably at higher velocities. Using a single or double monopropellant injection a la TAN (thrust-augmented nozzle) arrangement could give the launch thrust boost desired while allowing a wide range of fuel-air-oxidizer mixture ratios throughout the flight path.

Because it needed to be SSTO. Giving it drop-away-and-RTLS boosters for takeoff thrust and crossfeed would give it much better margins, enough to make up for the greater dry mass of an airbreathing system.

Re-entry heat. If you watch the landing videos it is already scorched black from re-entry before it nears the ASDS.