A close look at the Apollo 14 Lunar module on the Moon

Soylent Green Is People
I could theoretically achieve an escape of Earth's gravity well by only moving at 100 km per hour. If I was on a craft that could provide a constant thrust against gravity that allows me to achieve 100 km per hour against that gravity for an indefinite amount of time (years of continuous uninterrupted thrust), then I would eventually make it too the Moon while only moving at 100 km per hour.

Which is the principle behind the Space Elevator

Soylent Green Is People
By the way -- and sort of (but not directly) related to the topic -- the idea of "escape velocity" is sometimes misunderstood. Escape velocity is NOT specifically the velocity a spacecraft needs in order to break free of the earth's gravitational well...

Actually, yes it is, but there's a catch.

Soylent Green Is People
However, it does not take "escape velocity" speeds of 40,000 km/h (25,000 mph) to leave the Earth behind

The catch is that as gravity decreases as the distance from the center-of-mass increases, so does the escape velocity.

As a rule-of-thumb, escape velocity equals the circular orbit velocity at a given distance radius from the center-of-mass times the square-root of 2 (~1.4).

For example, an object in a circular orbit 200km above the Earth's equator would have an orbital velocity of ~28,024 km/hr. Escape velocity from that altitude would be ~39,631 km/hr. Similarly, an object in geosynchronous orbit would have an orbital velocity of ~11,069 km/hr. Escape velocity from that altitude would be ~15,654 km/hr. An object at the mean orbital distance of the Moon would have an orbital velocity of ~3,666 km/hr. Escape velocity from that altitude would be ~5,184 km/hr.

Of course, you weren't talking about circular orbits, but rather moving straight upwards at 100 km/hr and ignoring any lateral motion. Fair enough. Escape velocity for a given altitude remains the same. You are simply moving to higher altitudes where the escape velocity is lower. Let's ignore the Earth's motion around the Sun - and the gravitational force of the Sun and the rest of the planets (and stars!) for that matter. At an altitude of ~1,033,166,110 km above the Earth (somewhere out beyond Jupiter, which it took 1,178 years and 230 days to get to) the escape velocity falls below 100 km/hr. Beyond that, your elevator no longer needs to thrust. It will never return to Earth. Below that altitude, if you stop thrusting to maintain 100 km/hr vertical speed relative to Earth, then you will eventually fall back to Earth (though it may take a a few quadrillion years), hitting the atmosphere at ~40,000 km/hr.

We hope you enjoyed your ride...



ETA: A useful site

looks like mostly foil & tape.

like a homeless tweeker's shelter during a heat wave in Hollywood, really.

originally posted by: tulsi
looks like mostly foil & tape.

like a homeless tweeker's shelter during a heat wave in Hollywood, really.

There was in fact quite a bit of foil and tape.

The foil was reflective metalized Mylar and served as an insulator by reflecting away much of the solar heat radiation. The tape was Kapton Tape, which is used commonly in industry as a high-performance tape that could withstand high temperatures and other extreme conditions without failing.