Seret

Indeed. Reusable != spaceplane.

Which they receive from other humans.

Re-entry is risky, full stop.

You say that like it's not important!

Yes, if only because refuelling tons of little tanks is a pain. Part count might also be a good reason.

That's true, it's routinely taught to aircrew. I think most of the engineering bods are well aware of angle of attack as you say, just looking at a picture of an aircraft flying inverted sorts that one: Hell, old school water lifting wind turbines often use flat blades, and they seem to generate lift ok.

Tbh, the seats are so light that I often stick one on the outside of things like my robotic space tractors, just in case they need to go rescue a Kerbal.

They're the absolute most efficient way to ferry Kerbals around. Chair = 0.05t per Kerbal 1-man pod = 0.8t per Kerbal 3-man pod = 1.15t per Kerbal 2-man can = 1.25t per Kerbal Hitchhiker = 0.625t per Kerbal

Spoken like a true intern!

Ah well, best pack up civilisation now then. Shame, I was getting used to it.

"Exotic" is one of those words physicists use when they're talking about a phenomenon they don't yet understand. If they knew the answer to that question, they wouldn't need to slap such a vague label on it.

Sure, but I was responding to the suggestion that stealth would be non-existent because IR sensors would be able to spot anything. Radar and optical can be degraded by low-observables so I wouldn't rule stealth out, especially if you're trying to track something that can change its orbit, which kind of goes without saying for a combat vehicle.

They probably will, improving current driveshafts is a materials issue. A non-metal with better torsional stiffness per unit weight that was as practical as a metal would find its way into driveshafts quickly. Hey, I like pneumatics, pretty much everything I've worked on in my career has had pneumatic bits in it somewhere. However, they don't really scale up straight from windy tools to vehicle propulsion. Pneumatics aren't particularly efficient or lightweight (once you start chucking in compressors, reservoirs, surge tanks, etc) and fairly bulky, which is a no-no for AFVs. They're good for high-impulse intermittent use, but aren't suited to propulsion. Bottom line though, even if you had motors and power transmission that weighed nothing, having a bloody great heavy wheel and tyre at the end of your leg would be sub-optimal. Best idea is the one above to simply put the wheels on the hull instead of the end of the leg. Much simpler, completely doable without invoking future tech, and you'd be able to fold the legs when not in use to get a vehicle that was similar size to a normal wheeled one (so narrower and lower).

It's hard to tell if you're being sarcastic here or not. This is one is firmly in the realm of speculative physics. Engineers work with all the stuff physicists got bored with decades ago.

It's viable for very recently extinct species such as the Tasmanian tiger, where DNA is available, and the environment is compatible.

Exactly, the years are based on an arbitrary point. They're also not the same length as an actual year, the months don't match anything in particular, and a week totally arbitrary. A day isn't 24 hours long, and why 24 hours anyway? 60 minutes with 60 seconds is based on a counting system from the dawn of time. It's a hell of a mess, none of it actually makes any sense.

No, the current system is weird and ridiculous. We're just really comfortable with it. I agree that there's no pressing need to change, but only because we gain less from shifting to something more logical than the disruption would cause. Applications where logical systems are required (such as computing) already use another system, so the technical issues are already sorted. It would be nice to have a better system, but it isn't particularly necessary.

That would add a lot of complexity and mass to the leg, reducing efficiency. Running a driveshaft down the leg would be impractical so realistically you'd be talking electric hub motors. They're heavy things to swing around at the end of a leg (not to mention the high unsprung mass reducing suspension performance when using the wheels). You want to keep the mass of the legs as low as possible. Magnamoe's suggestion of putting wheels on the hull is a bit more practical if you want a hybrid wheel/leg vehicle.

This is only the case where the background is space, rather than something else. Combat isn't going to take place in interplanetary space, there's nothing there to fight over. Ground stations would probably have a tough time tracking things in Earth orbit thermally, they're looking through the atmosphere, which sucks for IR wavelengths. It could work on planets with atmospheres that were more forgiving in the IR. Vehicles in low orbits would have a good chance of picturing enemy against a space background, and being in a low orbit shortens the distance to the horizon, so you can be bounced that way. Radar tracking is still likely to be useful, as it can be used from both the ground and a high orbit. So stealth could well be tactically advantageous.

Is there a difference?

Except that the gravity well would bend the light towards the ship.

Deciding that any particular year should be year 0 is a totally arbitrary decision anyway. The only one with any logical basis would be the day the Big Bang occurred, and that's a completely impractical one for everyday use. Yes, the calendar we use in the west is derived from a Christian one, which is somewhat anachronistic given the general trend to rationalise weights and measures over the last couple of centuries, but so is the rest of our reckoning of time (hours, minutes, etc).

Sure, I don't disagree with any of this. The issue is whether on balance legs offer a net advantage. It's obvious they're an improvement over some types of terrain, but they're also sub-optimal over many others. To me it really seems like you'd only want legs if you were going to be spending a significant amount of your time in the roughest of rough terrain. For most vehicles that's not the case. I'm pretty sure legs will be remaining a specialist option, with wheels and tracks remaining the default. You do, unless you can somehow lengthen your legs during the stride! Consider the motion through space of a hip joint, it will rise to a maximum as the leg under it reaches the vertical position, with a minimum height when the leg is at furthest extension to front or rear. On a biped that's mitigated by twisting the pelvis during the stride, but it's just one of a ton of little extraneous movements that sap energy. Watch over the top of a body of people as they walk if you don't believe me. The heads do bob up and down, they sway side to side, etc. You can be hardass all you like, as long as you're keeping it civil, realistic and interesting. Which you are. Not in terms of processing power, no. It's a control problem, it's about finding the right algorithms. It looks like good progress is being made, in the last few years we've moved from robots that can walk to ones that can run. Are you talking about walking vehicles, or exoskeletons/human scale robots? That's definitely a consideration for the latter, although it's more of an issue for manipulators than locomotion. Robots with treads can get around our infrastructure fine as long as they can go up stairs, but being able to operate door handles, valves, etc designed for hands is a definite advantage for a robot. DARPA's recent rescue robot competition is a good example of why being anthropomorphic might sometimes be a good thing. If you're talking about vehicles, all the infrastructure is designed for wheels, so that's definitely a vote for wheels. Just look at the fraction of our urban spaces we devote to roads, and military transports are designed for roll-on roll-off. Most of the sources I'm looking at put standing at about 1.2 MET, while walking is more like 2.5. So walking takes about twice the energy of standing if you include the base metabolic load. Or to put it another way, standing takes about 20% extra energy above the baseline, while walking takes 150% more. So in humans the process of walking costs about seven times more than standing,

I strongly suspect on most terrain they'd be outperformed on fuel efficiency by wheels. Range is a very important factor for the military. Walking is inherently inefficient because you're having to accelerate the whole mass of the vehicle vertically, even if you can get your leg mass down low enough to make moving the legs relatively cheap. But yes, being aware of where the ground is is pretty important to a walking robot, along with the relative positions and accelerations of its legs, chassis, etc. There's a lot to process and react to at very high speed, which is why we're only just starting to develop reasonably capable ones now. Don't forget that all these Youtube videos of walking robots are advertising a commercial product. They don't show you the bits where the robot slips over, lands on it's robotic butt and can't get up again. I don't think there would be any point in bipedal locomotion for military use (exoskeletons notwithstanding). Four or more legs would give better stability, lower profile, lower ground pressure, more weight carrying capacity and more redundancy. Even wheeled AFVs tend to have six or eight wheels.

What sort of job at NASA duff you have in mind, or aren't you bothered? Does it have to be NASA, or would any space organisation do? Definitely go for a technical role if you join the air force though. Their training is good, and will stand you in good stead in the civilian job market.