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Advantages of an equatorial launch
I know that a launch from the equator to a zero inclination orbit gets all
of the advantage of the Earth rotation, but I was wondering if this advantage works the other way round too. In other words, does a reentering spacecraft from the due east equatorial orbit have significantly less demanding conditions than a spacecraft entering from a non-zero inclination orbit? Has this advantage ever been exploited? (The only spacecraft that I know of that reentered from an almost equatorial orbit was ESA's ARD, have there been others?) -- Remove 'nospam.' from mail address to reply. |
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Advantages of an equatorial launch
Alejandro Zuzek wrote:
I know that a launch from the equator to a zero inclination orbit gets all of the advantage of the Earth rotation, but I was wondering if this advantage works the other way round too. In other words, does a reentering spacecraft from the due east equatorial orbit have significantly less demanding conditions than a spacecraft entering from a non-zero inclination orbit? Has this advantage ever been exploited? (The only spacecraft that I Not much. However, the atmosphere rotates along with the earth, so there will be around a kilometer a second in it between retrograde and prograde orbits. For say a 45 degree inclination prograde orbit, it's only around 300m/s difference between that and 0 degree. Not in general a big number, compared to the getting on for 10Km/s that you need to slow down by. |
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Advantages of an equatorial launch
Alejandro Zuzek wrote:
I know that a launch from the equator to a zero inclination orbit gets all of the advantage of the Earth rotation, but I was wondering if this advantage works the other way round too. In other words, does a reentering spacecraft from the due east equatorial orbit have significantly less demanding conditions than a spacecraft entering from a non-zero inclination orbit? Has this advantage ever been exploited? (The only spacecraft that I know of that reentered from an almost equatorial orbit was ESA's ARD, have there been others?) The major advantage is that there is no "window". Since the spacecraft orbit always crosses the launch point (or landing point), you have to wait one orbit at most to land. Contrast this with the Space Shuttle. After launch its orbit is tilted to the Earth, so the Earth is spinning under it. After one 90 minute orbit, the launch site has moved hundreds of miles to the west. To land back where they started they have to wait, sometimes long periods, until their orbit crosses their landing site. Although the site moves for a zero inclination orbit as well, it moves toward you, not to the side. In fact it is exactly this "drift" that caused the Shuttle to look the way it does. Many early Shuttle designs were much smaller and used small, straight wings that were only effective in the lower atmosphere for landing. However when the Air Force agreed to support the project, they demanded many things, one of them being the ability to abort back to the launch site after a single orbit. Since their missions were primarily polar, the "drift" would be up to 1000 miles, and thus the Shuttle had to use the current delta-wing shape in order to dramatically increase re-entry manuverability. Maury |
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Advantages of an equatorial launch
"Alejandro Zuzek" writes:
I know that a launch from the equator to a zero inclination orbit gets all of the advantage of the Earth rotation, but I was wondering if this advantage works the other way round too. In other words, does a reentering spacecraft from the due east equatorial orbit have significantly less demanding conditions than a spacecraft entering from a non-zero inclination orbit? Has this advantage ever been exploited? I don't know about Earth, but this certainly applied to the Jupiter probe on Galileo. The had to land going with the rotation to reduce an enormous entry speed to something barely survivable. Of course this effect on Jupiter is much more signficant since it's bigger and rotates faster (12.6 km/sec as opposed to 0.46 km/sec at the equator) (The only spacecraft that I know of that reentered from an almost equatorial orbit was ESA's ARD, have there been others?) -- Remove 'nospam.' from mail address to reply. |
#5
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Advantages of an equatorial launch
"Alejandro Zuzek" wrote in message ...
I know that a launch from the equator to a zero inclination orbit gets all of the advantage of the Earth rotation, but I was wondering if this advantage works the other way round too. In other words, does a reentering spacecraft from the due east equatorial orbit have significantly less demanding conditions than a spacecraft entering from a non-zero inclination orbit? Has this advantage ever been exploited? Some more info on the entry of the Galileo probe.... From: http://www.agu.org/sci_soc/young.html The probe entered the jovian atmosphere at 6.54E N latitude, (just north of the equator). This near equatorial entry was dictated by the probe having to take advantage of the rotational velocity of the jovian atmosphere (which is greatest near the equator) in order to minimize the relative velocity between the atmosphere and probe during the high-speed entry. (The only spacecraft that I know of that reentered from an almost equatorial orbit was ESA's ARD, have there been others?) |
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