@leovinus2001 I made a list of Bellcomm' A.A. Vanderveen triple planetary flybys studies. Red dots are the papers readily available on the Internet (which I posted upthread, among "single flyby" papers)
Thanks for those. The list of papers is interesting. I had a quick look and with those titles, the following NTRS numbers come up. This is based on public information. If it says archive.org then you can find it there.
I did not check which of these NTRS reports were already attached in threads, and which overlap with your red dots, but that would be an obvious check to find more materials. If there is a list of NTRS numbers to read then we can go from there.
NTRS number, title, date
------------------------------
19790072271 ,Existence of a favorable 1976 dual-planet ballistic flyby, 1967,
19790072279 ,Families of 1977 triple-planet flybys, 1967,
19790072288 ,The existence of a 1981 triple-planet ballistic flyby, 1967,
19790072042 ,The 1975 mars-venus ballistic dual-planet flyby memorandum report, 1967,
19790072279 ,Families of 1977 triple-planet flybys, 1967,
19790072288 ,The existence of a 1981 triple-planet ballistic flyby, 1967,
19790072312 ,Low-energy 1977 triple-planet flybys with an inherent abort option, 1968,
19790072341 ,Verification of the existence of the 1978 triple-planet flyby opportunity - case 720, 1967,
"manned venus"
19650065385 ,Four studies in support of the manned venus/mars flyby project, 1965,
19670017910 ,Manned Venus Orbiting Mission", "1967-01-01", archive.org
19740079915 ,Preliminary mission study of a single-launch manned Venus flyby with extended Apollo hardware, 1967,
19790072066 ,Drop sonde and photo sinker probes for a manned venus flyby mission, 1968,
19790072080 ,Manned Venus flyby meteorological balloon system, 1968,
19790072165 ,Manned Venus Flyby, 1967,
19790072583 ,Experiment payload for manned venus encounter mission - venus tracking and data orbiter, 1968,
"MULTIPLE PLANET"
19640003362 ,The determination and characteristics of ballistic interplanetary trajectories under the influence of multiple planetary attractions, 1963,
19670002494 ,Multiple planet flyby missions to Venus and Mars in 1975 to 1980 time period", "1966-10-06", archive.org
"VENUS LANDER"
19790072657 ,Venus lander probe for manned planetary missions, 1967,
20110012039 ,"Progress Towards the Development of a Long-Lived Venus Lander Duplex System, 2010-07-26, archive.org
20110012899 ,"Progress Towards the Development of a Long-Lived Venus Lander Duplex System, 2011-05-01, archive.org
20120016535 ,"Long-Lived Venus Lander Conceptual Design, "2009-08-02, archive.org
20140017762 ,"Non-Cooled Power System for Venus Lander, 2014-07-28, archive.org
20160000342 ,"Thermal Control of a Venus Lander, "2015-10-27, archive.org
triple flyby
19790072279 ,Families of 1977 triple-planet flybys, 1967,
19790072288 ,The existence of a 1981 triple-planet ballistic flyby, 1967,
19790072312 ,Low-energy 1977 triple-planet flybys with an inherent abort option, 1968,
19790072341 ,Verification of the existence of the 1978 triple-planet flyby opportunity - case 720, 1967,
other
19720003877 ,Manned Mars lander launch-to-rendezvous analysis for a 1981 Venus-swingby mission, "1971-11-01", archive.org
19740072711 ,Comparison of Venus swingby and minimum-energy techniques for manned Mars orbiting missions, 1968,
19740072925 ,Velocity requirements for Mars stopover/Venus swingby missions in 1981, 1969,
19790072338 ,Venus swingbys for manned Mars missions during the 1978-1986 period, 1966,
20150012634 ,Interplanetary Aborts - The 1979 Venus Swingby vs. The 1976 Mars Flyby Abort Capabilities, 1967,
