# Re: Launches - directional

jbarker@arinc.com
Wed, 27 Mar 1996 10:30:28 -0500

```     From reading the initial responses to the message below, I think
there has been some misunderstanding.  The question was whether some
launches would be going in the direction of the west coast of
Florida.  As I read the question, the requirement is that the launch
pass over the west coast of Florida, not that the launch be toward
the west.

The most efficient way to launch a payload into orbit is to launch it
due east from the launch pad.  This takes maximum advantage of the
Earth's own linear rotational speed at the surface of the earth to
achieve orbital velocity.  (1,037 mph at sea level at the equator, 0
mph at the poles)  A launch due east from any of the existing launch
sites, with no other major directional changes, results in an orbital
inclination that is equal to the latitude of the launch site.
Kennedy Space Center is at 28.5 deg North so a launch due east from
there will result in an an orbital inclination of 28.5 deg.  A launch
from Vandenberg AFB in California is not permitted due to safety
constraints.

The basic equation to compute orbital inclination based on the launch
site location and the azimuth of the launch is:

cos (inclination) = cos (latitude) x sin (launch azimuth)

To avoid launching over populated areas, the minimum launch azimuth
from Cape Kennedy is 35 deg and the maximum is 120 deg.  The resulting
orbit inclinations (approximate) are 57 deg and 39 deg, respectively.
Note that the minimum orbital inclination is equal to the latitude of
the launch site.

A commercially owned launch site has been constructed on the east
coast of Texas.  A rocket launched from their could pass over the west
coast of Florida during its launch phase but the rocket would be at a
high altitude by then.

It is possible that a launch from Russia, Japan, China or India could
pass over the west coast of Florida on the first revolution but the
payload would already be in at least low earth orbit by then and not
in the launch phase.

The bottom line is that there is very little chance that a "launch"
would pass over the west coast of Florida.

Jeff Barker
jbarker@arinc.com

Subject: Launches - directional
Author:  seesat-l@iris01.plasma.mpe-garching.mpg.de at SMTPGATE
Date:    3/26/96 8:23 PM

>Message was resent -- Original recipients were:
To:
Seesat-L@iris01.plasma.mpe-garching.mpg.de--------------------------------------
-----------------------------------------

I am very interested in getting a schedule of the upcoming launches for the
next year that might be going in the direction of the gulf (west) coast of
Florida (imparticular over the Sarasota area) and what possible times they
might be observed in that area.  If you could send me that information, I
would very much appreciate it.  Thank you.

```