The SLS has one thing the currently-projected private sector boosters don't have: maximum payload capacity. The Falcon Heavy is only supposed to hit 53,000 kg to LEO ("only"). SLS is supposed to be around 100,000 kg. It's basically the Space Shuttle, and those were damn powerful engines. They just had the drawback of hauling 68000 kg of orbiter on every trip.

Falcon X might beat SLS, but that's almost purely concept art at this point. But then, my confidence in the SLS project isn't really any higher.

They certainly aren't in the US.

The value of a dollar is the ability to pay one dollar's worth of US Federal taxes.

Visited? Um, basically all of them?

I think you meant "edited".

I've seen the inverse argument made. That because things get smaller with distance, it can't be an airliner coming east. The enlarging of the contrail as it disperses is competing with the shrinking with distance. Intuition about which should be winning fails.

Because Phoenix is 375 miles from Los Angeles? Flight records for a later run of flight 808 show it beginning its descent about 25 miles west of the California/Arizona border. The flight took a good 50 minutes to get from 37k feet over Los Angeles to arrival on the ground at Phoenix.

They also don't turn the engines off to make the plane go down.

This is incorrect. Each manned Apollo mission used a single Saturn V. (Except for the Apollo 7 test flight, which used a Saturn IB.) Orbital docking occurred between the command/service module and lunar module launched on the same rocket.

Agena boosters were modified to practice docking during the Gemini program, but had no direct involvement in Apollo.

You're kidding, right?

Obama has proposed removing funding for the Constellation Program in the 2011 budget. The budget cuts haven't taken effect and are still being argued over. The reason NASA hasn't built them is that NASA is years behind schedule.

In five-ish years, SpaceX designed, built, and flew a prototype two-stage rocket. In five-ish years, NASA put a guidance system on an existing STS SRB, and launched a fake second stage.

And you are still confusing two separate launchers. The Ares I is a LEO launch vehicle, an orbital taxi. It can no more get one to the Moon than the Falcon 9. It can ferry people to a lunar transfer vehicle, but so could the Falcon 9.

NASA can't get anywhere using NASA's old technology, so SpaceX is still ahead on that score.

You are misinformed. The Ares I rocket is just a LEO launcher. It is an extended space shuttle solid rocket booster with an upper stage powered by a single Saturn V motor. The technology in it dates to the mid-1970s or even earlier.

The Ares V is a heavy-lift booster that outclasses anything built. Or it would if they'd actually try building one. It is a STS External Tank with five motors off the Delta IV under it and two STS SRBs attached to it. The upper stage is powered by the same Saturn V derivative motor used on the Ares I.

Both programs started development circa 2005 (SpaceX was only founded in 2002). SpaceX has delivered a working launch vehicle. NASA has launched what was literally a slightly modified SRB out of the Space Shuttle inventory as the Ares I-X, and is unlikely to launch the real thing until 2017. The Ares V hasn't even begun to leave the drawing board.

SpaceX has a working satellite launcher that can be made man-rated. The Constellation program has nothing.

Those claims are wrong. The force on a solar sail due to solar radiation pressure is about a thousand times that of the solar wind.

The solar cells are going to be absorbing a small fraction of the incoming photons. If the sail is designed properly, the rest will be reflected in a controllable direction.

Your assumptions are wrong, and the model is correct.

MESSENGER has used its mostly reflective solar panels to make deliberate course changes. The basic physical principle is already proven, not just in the lab, but in space. JAXA is examining the practicality of building large solar sails, not whether they will work at all.

2000 was not the last year of the 1990s, 1999 was.

2000 as the end of the 20th century works because it's counting time since the switch to positive integers, and there was no year zero. Decades such as the 80s, 90s, and whatever we end up calling the period from 2000 to 2009 (inclusive) are not set from the origin, but are based on the tens digit of the year. 2000 may have been part of the 20th century, but it wasn't part of the 90s.

Also note that kimvette made an exception to include a movie released in 2000, which establishes that the conventional 1990-1999 definition of the 90s was intended.