Bill Phil

While Mars is certainly not the greatest target for colonization, I wouldn't say Titan is, either. For one, there's a factor of distance. It orbits Saturn. It will take quite a long time to get there. Not only that, but the atmosphere can be an issue. Being a very cold, dense atmosphere, it can easily take heat away. Although that may not be a serious issue... the distance from the sun and the haze prevents effective use of solar arrays, so you'll need reactors, which would have to be designed for that environment. Beyond that, there's the low gravity. Mars has that problem to an extent as well. We have virtually no data on low gravity's effects on child development.

Most colonization proposals have a dedicated shield for radiation. Mars and Lunar colonies generally use the local dirt to shield from radiation. Orbital colonies generally propose using large amounts of mass for shielding, sourced from asteroids/the Moon. Radiation shielding is mostly a matter of mass. It's a problem on flags and footprints missions due to the stringent margins and low payload mass fractions for the vehicle. Colonies won't suffer nearly so much. The only thing that makes it a show stopper is the sheer mass that has to be moved. For orbital colonies, this is easily 95% of the total system mass. There are ways around this by using active radiation shielding, but that needs to be developed first. Even on Mars or the Moon you need to cover your colony to shield it, unles you build underground.

I remember that someone I know said that there were some points that looked exactly like KSP (at least to him).

And we can build fusors in our garages.

Congratulations?

The industrial capability exists. Even if it doesn't they could acquire it. The bureaucracy just can't support that many flights. Also, they'd need to build new engines very soon, and that's not very likely to happen.

When you're watching a KSP video and try to move the camera.

Yeah. A black hole "core" and some method of suspending the surface of the planet would explain it... Although, in truth, there's a lot wrong gravitationally with the whole solar system, more than just mass. Things like how the Jool system is unstable, and that Duna and Ike would be a binary system.

Huh... Interesting.

Detroit of Gibraltar? Autocorrect? Anyways. Neat video.

The Atlas V has had one partial launch failure. Ever. And even then the payload entered orbit. (75 launches since 2002) A lot of the Atlas V is unrelated to most previous Atlas family vehicles... The Delta IV has had one failure in all of its launches as well. Not quite as successful, but it did put one of its payloads into orbit (a demosat). Bash ULA all you want, their rockets are good. That's built on decades of experience between its constituents.

Is there anything to corroborate that? I can see why they might build the upper stage first (although I would build the first stage since it's shape is relatively simple). Anyhow... at this point SLS should've been flying... I think it would be prudent to drop it and focus on actual space probes. Not only could that help stimulate the launch market (billions of dollars per year on more space probes, which means more payloads) but it will also lead to more science in the end. I'd love another Saturn Orbiter, perhaps a more advanced Titan probe as well (airship? submarine?). I wonder if FH can loft EC to a similar trajectory as SLS...

I don't know about the upper stage. It's more complex and will probably need a lot more development than the booster. The booster is essentially a scaled up F9 first stage, albeit with new propellants and engines. But it's much less complex than the upper stage. I can see it being under construction very soon for early tests (Grasshopper tests, basically), and the upper stage still being designed and engineered at the moment, but with test articles rolling out sometime, perhaps before the next decade. It's being built, but it's two vehicles, essentially, that make up the system.

Yeah. The hard part is the upperstage/ship.

Rocket equation is exponential. With no upper stage/core/payload that needs to be lifted, the dry mass is reduced, increasing the mass ratio to a decent amount. Stages are very light compared to their max propellant loads. Even with just a little propellant left, you can get a lot of Dv. It's not pushing anything but itself.

FNAF is interesting. Really it stops being scary after a while but there's a lot of stress while actually playing, if not fear.

OP: You should link to more articles about this topic. Here is a pretty good one: http://www.nss.org/settlement/physicstoday.htm

Suborbital tests are usually spaceflights...

Mars is dangerous to colonize as well. Not really any more dangerous, though. Both will kill you in a matter of seconds to minutes if unprotected. Pandora is actually slightly worse due to dangerous wildlife... of which Mars has none. Also, just because it has water, oxygen, trees, and animals doesn't make it a good place to colonize. For one thing, there's distance. It takes a starship to get there. Another issue is the huge CO2 percentage in the atmosphere. Pandora would require moderate terraforming (even then, still a gargantuan effort for little gain) to be a decent target for colonization. Mars would require more terraforming, but at least it's in this solar system. It'd be far better to just build orbital colonies and ignore planets (at least for housing purposes), but that's a discussion for another time.

No, that's astronomy, not physics. If I recall, it wasn't necessarily lack of oxygen, but the presence of dangerous gases. Even a few percent of CO2 could prove problematic. According to the "Avatar wiki", CO2 percentage is almost 20. That is deadly. It's cruising speed is about 70% lightspeed. And mass doesn't increase all that much until you hit higher fractions of C. Yes, there is an increase, although it really isn't relevant to how a rocket works. What matters is mass ratio, if the propellant is increasing in mass and the vehicle is increasing in mass, then, if both are increasing in mass by the same amount, the mass ratio should be identical. Chemical rockets wouldn't even get you to .7c with or without the increase in mass. They're puny. Current costs of antimatter are irrelevant to future costs. For example, the cost of certain metals just 150 years ago was prohibitive. Now, many of those metals are ubiquitous (aluminum being a good example, it used to cost more than gold, and then, its price dropped dramatically after new methods were discovered of extracting it; over a four year period its price dropped by an order of magnitude from 1855 to 1859). They may have large solar arrays in low solar orbit connected to antimatter factories or something. My main gripe here is that they still haven't built a laser array at Alpha Centauri. That's how they depart and brake from/into the Solar System, but they brake with antimatter. Presumably they have the means to set up a large mining operation, which means that it shouldn't be impossible to save on antimatter by using another laser array at Alpha Centauri. Yeah. High price means small market. Provided that it's an unnecessary utility. In the Avatar universe, unobtainium isn't something they just want to have, they need to have it. Mainly to solve energy issues, apparently. Also, presumably the economy has grown considerably (it's large enough to support a fleet of STL starships), so 20 million may not be as much as you'd think in that economy (another factor to consider is inflation). Pandora is too hazardous to truly colonize. For one thing, despite there being greenery, the atmosphere is dangerous. Another issue would be the sheer distance and difficulty of supporting the colony. A small mining base is much cheaper, paradoxically... they don't need that many people. It's mostly automated. Although there is presumably a few reasons for keeping people around. They're not an actual military, and, like you said earlier, it's expensive to bring all that stuff from Earth. Perhaps there is no local manufacturing to speak of. The square cube law is kind of over-rated. While it does apply in general, it ignores things like actual material strength and simply refers to the ratios. We likely have the materials required to build something like it, although not the required joint tech or power source, which is the real issue. I could see its usefulness, considering the forests of Pandora. But without a good power source, it's not going to be useful. Because it's probably cheaper to try to negotiate than replace all the military hardware they might lose in the ensuing battle (if not actual vehicles, certainly some lives would be lost along with quite a bit of other resources). Again, very expensive to replace. Might be a bit cheaper to just send a few "cloned" bodies there and put human minds into them than actually engage the Navi. Yeah, the floating mountains where kind of ridiculous. I was under the impression that they had high concentrations of unobtainium, which, in the movie's world, induces floating. I don't think that would happen in real life, but, whatever. Lower gravity doesn't imply greater mobility for humans. Just less resistance when doing things. Maybe most of the characters' muscles have adapted to the slightly lower gravity. Yeah, that was just kind of dumb. Although it's not really a science issue, since it can be assumed that the Navi probably aren't very good at taking down helicopters.

He's just wishing them luck. That's perfectly fine. Also, he could probably buy SpaceX.

Not really. It could be moving retrograde, which would result in very high relative velocity. Although I haven't seen Gravity in a good while, so I don't know if there are any specific details in the trajectory in the movie.

Apollo 18 is based on a conspiracy theory, at least somewhat.

Yeah. Light pollution from cities has ruined the nighy sky already. A space disco ball won't do anything.

It was alright. Kind of sad, though.