On my trawls through the NTRS I've come across several oblique references to cislunar Pegasus missions, now I know about the earth orbit missions where the Pegasus satellite was attached to an S-IV stage and launched along with a boilerplate Apollo CSM.

However from the hints I've found the cislunar version was going to use a Saturn Ib\Centaur as the launch vehicle, presumably with the Pegasus attached to the Centaur.

While the objective is clear, measure meteorite impacts in lunar space prior to Apollo, what is not clear is the mission plan, was the Pegasus going to be sent on a simple flyby of the moon, or was the plan to place the satellite in lunar orbit, or some combination of the two?

Does anyone know which of these mission plans is the one NASA was planning to carry out?


Graham

Given that any meteoroid statics measuring mission needs LONG exposure time to get enough data onlarger, thin tube penetrating particles, it seems plausible that they were thinking of using a lunar flyby to put the spacecraft in a mult-day high perigee orbit data. The trick with any such orbit on a spacecraft with low maneuverability (expensive and unreliable then) would be to design a flyby that puts the spacecraft in a stable enough high orbit that lunar peturbations or close flybys wouldn't eject it inthe wrong direction at the wrong speed.... FLING!..... HOME RUN!

sounds interesting. any link?

I've found references in three online documents to date. The most explicit is one which discusses trajectories for spacecraft launched using a Saturn 1b with a Centaur upperstage.

One of the references in the document is a study of launch opportunities for Cislunar Pegasus missions.

The document itself is called, 'Launch windows for two types of orbits synchronous with the lunar period' (1.8mb).

There is also a brief reference in a description of the Saturn 1b/Centaur launch vehicle which I posted about in the Mars section of the forum.

There is also another reference in a planning document I have which discusses schedule constraints for advanced Apollo missions, this mentions a flight using Saturn 1b 212 (Centaur Pegasus 212) and states that it might not be in time for use with Apollo, but could be used to get data for a lunar survey mission which I think is the one where a CSM and an LM fitted with mapping cameras were going to spend a month photographing the lunar surface to prepare for long term lunar exploration (essentially a manned LRO).

The December 14, 1964, issue of Aviation Week & Space Technology had a nice two-page article "Pegasus Circumlunar Mission Under Study." The details of the program were very fluid at the time, so different scenarios were mentioned:

"Essential mission would be on an Apollo trajectory with a circumlunar leg and return to Earth over a seven-day period.

There are, however, several alternate trajectories whose use would permit long exposure times of up to several months, and these are under active consideration instead of a purely circumlunar flight.

The alternatives include a highly elliptical orbit out to 240,000 mi. to achieve a continuing survey of meteoroid flux in areas through which the moon normally might pass. The relative apogees of each orbit are not yet resolved."

The purpose of the mission was to determine the actual meteoroid flux, to feed into the design of the Apollo spacecraft meteoroid bumper structure. Saving weight over the baseline design was considered a very important target to increase the propellant margin for the Apollo spacecraft.

There was the inevitable attempt by scientists to add other scientific instruments to the mission, but NASA viewed this as an engineering experiment only. In the end, the lunar meteoroid flux was determined by the Lunar Orbiter spacecraft.

Thanks for the information, at least now I know why I could not locate much more than what I discovered as this one must have been shut down fairly quickly after the plan was decided upon.