Fuzzy Dunlop

It wouldn't be able to do anything there though. Miniaturization is great but some things simply have to be big enough - particularly solar pannels, communication antena and telescope mirrors (all three of which simply need the area to gather radiation). And Humans aren't getting any smaller either.

I think the aerodynamics has to come relatively soon. The longer they wait the harder it will be to change it

0.21 was really laggy for me, which is riduculous as 0.20 was fine and I am playing on a beast of a PC. 0.21.1 seems to have solved this completely.

Yeah acctually the vast majority of US commercial launches have used solid upper stages. You can easily plan the trajectory by adding balast to the payload to make it up to a nominal weight. The RCS system of the payload is almost always enough to fine tune an orbit if nessecary.

The O-rings were never designed to fail, and suriving a failure just because a load of ash built up in the hole is a lucky fluke that could never have been predicted and should never have been relied upon. Basically as soon as NASA realised that a saftey critical component was failing they should have grounded the shuttle until they solved the problem. Instead they decided that, since the failures hadn't actually killed anyone yet, they were in fact safe.

Challenger didn't explode so much as it was ripped apart by wind when it flipped sideways at Mach 2. The more robust SRB's both kept firing and seperated from the rest of the stack, they then self-destructed on command from the range saftey officer. It didn't explode, but when the O-ring failed a jet of superhot gas burned into the external tank.

Yeah but where?

Photosynthesis really isn't that efficient

The first things to evolve photosynthesis were bacteria, some of these are still alive today and are purple - because they absorb green light. It's possible that these bacteria were once so dominant that most of the water only let through purple light. Then green bacteria evolved to make use of the spare purple light. Later the green bacteria became the chloroplasts in plants and at some point the plants began to dominate.

Half-Life 2 was originally supposed to have an opening that detailed what happened in the years since Black Mesa. First off the portal storms get worse and worse, random aliens from xen start appearing all over the earth's surface. Populated areas are able to deal with this but rural areas are overun with bullsquid, antlions and headcrabs. Gradually society starts to collapse and starving people flee to the safety of the largest cities. The world's millitary is largely focussed on defending these urban centers and many bases are abandoned or cut off. Then one day the centers of all the major cities collapse into giant sinkholes, they are replaced with mile-high towers of blue metal, seemingly appearing from nowhere. From the citadels issue forth a swarm of insectoid bio-mechanical machines. Clouds of gunships blot out the sun, columns of striders march into the cities. Earth attempts to resist but they are completely unprepared and can't match the firepower of the killing machines. Most millitary units are overwhelmed by gunships and hunters before they even realise what's happening. As the onslaught unfolds a certain Dr. Wallace Breen (a prominant figure in the defense against the portal storms) claims to be in contact with the invaders. He says the Combine offer peace if humanity will only lay down their weapons and allow them to assume control. Civilization was on the brink even before the invasion, now, utterly blindsided, Earth surrenders. The Combine appoint Dr. Breen as their representative, he starts recruiting troops to form a security force. The Combine begins integrating humans into their millitary and harvesting earth's resources. They conquered earth with sheer firepower, giving the people and choice between submission and annihilation. However they don't want to destroy humanity, we're useful to them. Instead they plan to hold on to earth with a combination of mass surveillance, strict pollicing and brutal terror (Ravenholm).

I'm completely guessing here but I think the Merlin's physical size is probably a signifcant issue. Rocket engines are complex machines which take many man hours to build, this would only be exacerbated by having a huge, unwieldy structure. Merlin is slightly taller than an average man and weighs about 700 Kg, one guy can push it around on a trolley, I'm guessing most components can easily be lifted and installed by hand, everything is easily accessible. Overall I think you would need far more faffing with about cranes, jacks and scaffolding if you were building a much larger engine, which costs time and money.

The landing itself barely uses any fuel at all, its the getting back to base bit that's the drain.

I was messing around with this in KSP tonight, as a challenge it varies from moderately difficult to utterly impossible. Landing isn't too hard (well it is but only because the high gravity of Kerbin punishes mistakes - my best attempt ended up landing, bouncing back up then slaming sideways into the VAB). The main issue is getting back to the KSC, which becomes very difficult if you're moving downrange fast enough. Also it's very hard to eyeball it, I once overshot KSC by at least 20 km.

He means before any engines are lit only the SRBs are connected to the pad, and they hold up the entire stack.

KSP is quite misleading because the liquid rocket engines have much less thrust to weight than real life; from memory a mainsail is about 25:1 whereas a Merlin D is more like 150:1. KSP needs this because otherwise every single rocket would be an SSTO, but it does cause a few anomalies compared to real life. The space shuttle SRBs are absolute monsters, they each weigh something like 590 tonnes fully fueled, which put together is much more than the external tank and orbiter combined. They provide about 80% of the liftoff thrust. What KSP doesn't really model is how much power SRBs pack in a small (but very heavy) package.

Well you're right that the engines are the heaviest part of the stage at about 7.7 tonnes, the whole thing having an empty weight of about 15 tonnes. But an empty space shuttle SRB is about 91 tonnes.

Well the reason you don't use parachutes is because you want to land on the point back at base rather than splashing down at some random spot in the ocean. Landing at an exact location is just about the only thing the space shuttle got right. Finding and retrieving large rocket stages can become very expensive. Put it this way - the shuttle eneded up with a load of comercial divers on staff (to secure the underwater sections of the SRBs), these are not the kind of people you can afford if you are trying to build a low-cost launch system. The other point is that it doesn't require that much fuel to land a rocket, the mass of the empty 1st stage is well under than 10% of the mass at launch. You only really need 1 of the engines running at low power to guide it gently to the ground. Thats not true, the shuttle SRBs are made of 2" maraging steel, the Falcon 9 is made of the thinest aluminium alloy they can get away with. In fact it's doubtful that a Falcon 1st stage could survive the forces the SRBs undergo when they hit the water (which is another reason they don't really want to use parachutes). It's worth noting that even after the SRBs were fished out of the sea they still had to be disassembled, shipped to Utah, overhauled, reloaded with propellent, (which is difficult dangerous and expensive), shipped back and put back together again. With a liquid booster all you should have to do is check it out and refuel it.

That's got to be the largest pure SRB 1st stage since Titan IV retired.

I think he means gravity losses on the upper stage, where an extra 10t more payload can matter. I think that's why Atlas 5 uses a duel engine centaur when flying to LEO and single engine when flying to GTO.

Yeah that's kind of what happens, it's just that the microwaves play a major role in supressing nucleation. As I said it doesn't actually cool anything down (in fact due to the latent heat of fusion it releases heat) but it can make stuff freeze on command. You can also do it with magnets.

There is a kind of freeze ray, but it's actually not a cooling ray. Basically it is possible to cool a liquid below the point where it should normally freeze (called supercooling). It may be possible stabilise a supercooled liquid with microwaves, so when you switch the microwave off it instantly freezes.

Which is why most of the most promissing future propulsion technologies rely of a controlled nuclear explosion

Higher engine thrust to weight ratio and better ISP

1) The SpaceX rockets use only kerosene/liquid oxygen, which is a lot more dense than liquid hydrogen. 2) Saturn V uses 3 stages, 2 of which are liquid hydrogen. More stages tends to give a better payload fraction, as does using liquid hydrogen. Most rockets are only 2 stage because thats cheaper.

Isn't empire state building way too small? Edit: feet and meters mix up possible? I think maybe the Washington Monument would work better