A question I'm embarrased to ask - earth's spin

On Tue, 05 Dec 2006 08:38:56 -0500, Roy Smith wrote:

Bob Noel wrote:
Note that rocket launches are to the east (and why they try to launch
them as close to the equator as possible).

I think equatorial launch sites are only advantageous for certain types of
desired orbits.

In any case, this is an area in which the Europeans have the Americans
beat. We launch from Florida, at about 30N, they launch from Kourou,
French Guiana, at about 5N.

Boeing launches from the equator.

http://www.boeing.com/special/sea-launch/

The Earth's spin gives a "head start" of about 900 nautical miles per hour
towards the east. This tapers off as the launch site latitude increases, IIRC,
it's a function of the cosine of the latitude. So Cape Canaveral gets a ~800
nmph boost.

The amount of assistance this gives any particular launch depends on the
inclination of the orbit...the 'tilt' of the orbit plane relative to the
equatorial plane. The more inclination, the less benefit from the Earth's spin.

Geostationary orbits (those which allow a satellite to hang stationary relative
to the Earth's surface) are probably the most valuable; these have zero
inclination and thus benefit the most from a lower-latitude launch site.
Sun-Synchronous orbits, which are used by imaging satellites, have inclinations
over 90 degrees and thus see no benefit from equatorial launch. The US uses
launch sites in California and Alaska for these types of launches.

Airplanes fly relative to the atmosphere. Since the atmosphere moves with the
Earth's spin, aircraft see no advantage from eastward flight.

Ron Wanttaja