Subject: Lunar Surface Logistics From Selenocentric Equatorial Orbits (SEOs)
From: Daniel Adamo <[email-masked]>
To: ATIG <[email-masked]>
Date: Mon, 27 Mar 2017 11:48:50 -0700

ATIG Members-

With a new Presidential administration in Washington D.C., debate over what
orbit to select for human space flight (HSF) infrastructure in the "cislunar
proving ground" has only intensified since 2017 January 20.  In assessing
lunar landings from the subject SEOs, the attached white paper makes no
assumptions regarding their accessibility from Earth in the context of any
SLS/Orion or other specific logistics system design.  Nevertheless, as the
attached paper is reviewed, I'd urge any HSF policy stakeholders among us to
consider two conclusions from my previous cislunar trajectory research since
2008.

1)  Particularly in a HSF context, cislunar orbit accessibility from Earth
isn't exclusively dependent on a cherry-picked optimal total
change-in-velocity.  Rather, the frequency with which loiter-free viable
transits between Earth and a cislunar orbit can be initiated and concluded
must be considered too.  Opportunities to begin and end such transits arise
on a daily basis for SEOs with radii near 10,000 km.

2)  Retrograde SEOs (a subset of lunar distant retrograde orbits) are the
closest stable orbits to Earth from which multiple interplanetary transits
may begin and end without undue propulsive penalties or delays.  If the
cislunar infrastructure is to serve as an interplanetary gateway logistics
node, placing it in an orbit not well aligned with the Moon's geocentric
motion will render it a logistic albatross in the long run.  Given the
investment being contemplated in cislunar HSF infrastructure, the virtues of
a stable orbit venue cannot be overestimated.

I'll be happy to supply papers supporting these conclusions on request, but
they're probably also accessible from the ATIG archives at
http://www.aiaahouston.org/adamo_astrodynamics/.

-Dan