Author Topic: Molniya Satellites - Scott Manley  (Read 1228 times)

Offline catdlr

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Molniya Satellites - Scott Manley
« on: 10/23/2023 06:42 pm »
The Massive Molniya Satellites - How The Soviet Union Solved Satellite Communications Their Own Way.

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Oct 23, 2023
Part 4 of a series on communications satellites. The Soviet Union had a big advantage in launch vehicle capability, but, while the US had adapted the Delta to launch small satellites into Geostationary orbits the R7 which had carried spacecraft to the Moon and Venus was not capable of doing the equivalent without significant redesign. Instead, the Soviet Union's scientists came up with their own solution which had some advantages for covering the massive territory of the USSR.

The Molniya satellites would be in a highly eccentric orbit that spent about 6 hours per day over the USSR, this orbit was easier to reach and this let them launch spacecraft 40 times the mass of the American satellites. but as communications platforms they were no more capable.

Most of this information comes from Boris Chertok's Memoir - Rockets and People, specifically volume 3 "Hot Days Of The Cold War" - NASA has translated this and I highly recommend it.  SOURCE

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Offline Newton_V

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Re: Molniya Satellites - Scott Manley
« Reply #1 on: 10/23/2023 07:13 pm »
Good video.  He mentioned the 63.4 deg inclination, which keeps the line of apsides from rotating, and at 20:00 mentioned the effects that solar and lunar perturbations can have, but I still can't seem to find information about the effects of longitude of ascending node (LAN).  Somebody told me years ago that the Soviets had some of their SVs unexpectedly reenter (I guess perigee was decreasing faster than the ability to do anything about it), and that it was due to the LAN.  Since the Earth is essentially "pear-shaped", I believe the location of perigee affects the orbit perturbations, but can't seem to find any information online about it. 

Offline LittleBird

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Re: Molniya Satellites - Scott Manley
« Reply #2 on: 10/24/2023 08:24 am »
I look forward to watching that. I'll be interested to see if he mentions the 1958 Hughes study of a Molniya-type orbit comsat: https://hughesscgheritage.wordpress.com/2015/05/04/pre-syncom-communications-satellite-studies-dr-boris-t-subbotin-jack-fisher/

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The Hughes study, “Satellite Communications, An Initial System for Global Communication Via Satellite Relaying,” is documented in a brochure written by the Communications Systems Laboratory personnel and Dr. Lutz. One key contributor was Donald Miller, who later in the 1960’s worked with Dr. Rosen’s group. The brochure is undated but apparently completed in early 1958. It described a system of satellite communications that could have been provided with 1958 technology. This pre-Syncom study was an attempt to indicate to the U. S. government and military that Hughes had the interest, resources, and technical breadth to conduct the analysis, design, and construction of communication satellites.

The orbit selected for this study maintains the satellite apogee (maximum altitude) of an elliptical orbit continuously over the northern hemisphere to maximize time available for communications for the most populous regions. This type of orbit was later selected for the first USSR domestic communications satellite, Molniya, launched in 1965, and thus became known as a Molniya orbit. By selecting an orbital inclination at 63.4 degrees the apogee would remain fixed over the northern hemisphere and with a period of 12-hours the Molniya satellite could provide 8 hours of communications service.

The Hughes 1958 study adopted a Molniya-type orbit with a period of 4.8 hours, an apogee of 9500 miles, and a perigee of 500 miles as limited by the launch vehicle capability of that time.
With a modest initial investment, it was projected that the satellite could be placed in service within one year.
« Last Edit: 10/24/2023 11:57 am by LittleBird »

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