Genova/Aldrin free-return Earth-Moon cycler (interplanetary cruise ship, 3:1 lunar resonant)

genova-aldrin-2015-em-3petal-cycler · source: literature · validation: V0

Signature

Bodies: E-Moon
Primary: Earth
Sequence (canonical): E-Moon
Sense: n/a
Orbit class: Cycler
strict cycler (infinite returns)
Cycler class: non-keplerian (CR3BP)
Trajectory regime: ballistic
Maintenance ΔV band: unclassified
Model assumption: bicircular
Period: — yr ( × E-Moon synodic)
The paper describes a circumlunar periodic orbit with Earth encounters every 7 or 10 days and lunar encounters every 26 days. The 26-day Moon-encounter cadence corresponds to one lunar sidereal period (27.3 d) modulo phasing; the cycler is qualitatively a 3-petal (3:1) lunar resonant trajectory in the Earth-Moon rotating frame. The single "period" of the cycler as a whole is not isolated in the accessible abstract — left null with the cadence captured below as legs/encounters.
Priority date: 2015-08-09

V∞ at encounters

E (encounter 1): — (not published)
Not tabulated in accessible material (NTRS abstract + Semantic Scholar landing page; full PDF inaccessible to this ingest). Per spec §16.1 honesty rule, left null with the gap noted rather than guessed.
Moon (encounter 2): — (not published)
Same — not in the accessible abstract.

CR3BP orbit identity

Family: 3:1-lunar-resonance
Mass ratio (μ): 0.01215
Jacobi constant: —
Period (non-dim): —
Stability index: —

Geocentric inclination 24° (p.8); Moon-TOD-frame inclination ~174° (p.8), both backfilled 2026-06-10 from the full PDF. Other geocentric elements (a, e) are not tabulated in the paper.

Orbit view 2.5D ecliptic projection

Not renderable from current data. This is a rotating-frame (CR3BP) periodic orbit. A faithful render requires numerical propagation of the synodic-frame state, which the catalogue does not yet publish as a sampled path — so no stand-in ellipse is drawn (drawing a heliocentric ellipse here would misrepresent the dynamics). The CR3BP identity (Jacobi constant, period, stability) is tabulated above.

model: spacecraft: idealized coplanar ellipse

3D view not available for rotating-frame (CR3BP) orbits.

Legs (trajectory segments)

E → E: 7 d, 0 revs
Earth-to-Earth encounter cadence: "close-Earth encounters every 7 or 10 days" per the NTRS abstract. The 7 / 10 d alternation is a feature of the 3-petal geometry with solar-gravity phasing.
E → Moon: 26 d, 0 revs
Earth-Moon encounter cadence: "Lunar encounters occur every 26 days" per the NTRS abstract.

Definition status

incomplete — core fields missing or known-unknowns tracked below

Known-unknowns (5)

Values we expect to exist but have not yet filled (distinct from "not applicable"). Tracked per upstream docs/spec.md §16.6.4.

trajectory.segments [uncertain]
Segment topology is a CR3BP-model-mismatch placeholder. The patched-conic legs[] abstraction the rest of the catalogue uses is a poor fit for this circumlunar periodic orbit (Jacobi constant, not V-infinity, is conserved). The 7/10-d Earth and 26-d Moon cadences are captured as cartesian-state cadence arcs; the true periodic-orbit decomposition needs the full Genova & Aldrin 2015 PDF (inaccessible to this ingest).

source: Genova & Aldrin 2015 (AAS-15) full PDF
vinf_kms_at_encounters [unknown]
V-infinity at Earth and Moon not tabulated in the accessible NTRS abstract / Semantic Scholar landing page (full PDF inaccessible). Geocentric, not heliocentric, energy applies in this CR3BP model.

source: Genova & Aldrin 2015 (AAS-15) full PDF
orbit_elements.cr3bp.jacobi_constant [not-applicable]
RESOLVED 2026-06-10 (full PDF read): no Jacobi constant exists for this orbit because it is NOT a pure CR3BP periodic orbit — Genova & Aldrin 2015 p.3 state the 3-petal cycler exists only when solar gravity is added (bicircular Earth-Moon-Sun model) plus station-keeping. model_assumption reclassified cr3bp -> bicircular. The cr3bp.* block is retained as null for schema shape but is structurally inapplicable; a bicircular periodic-orbit IC would require a separate numerical search or a future paper publishing rotating-frame states.

source: Genova & Aldrin 2015 (AAS-15) p.3 — orbit does not exist in pure CR3BP; bicircular model required
orbit_elements.cr3bp.period_nd [not-applicable]
RESOLVED 2026-06-10: inapplicable — not a pure CR3BP orbit (bicircular, solar-perturbed). The physical super-period is the 553-d apsidal rotation (period.apsidal_rotation_days), not a CR3BP non-dimensional period.

source: Genova & Aldrin 2015 (AAS-15) p.3/p.5
orbit_elements.cr3bp.stability_index [not-applicable]
RESOLVED 2026-06-10: inapplicable — not a pure CR3BP orbit. The orbit is maneuver-maintained (20-62 m/s/cycle station-keeping), i.e. not naturally stable; a CR3BP monodromy stability index does not characterize it.

source: Genova & Aldrin 2015 (AAS-15) p.3/p.4

Primary citation

Genova, A. L. & Aldrin, B. (2015). A Free-Return Earth-Moon Cycler Orbit for an Interplanetary Cruise Ship. AAS/AIAA Astrodynamics Specialist Conference, Vail CO, August 9-13, 2015.

URL: https://ntrs.nasa.gov/citations/20150018049

NASA report number ARC-E-DAA-TN22765 per the NTRS metadata. The specific AAS paper number (e.g. AAS 15-XXX) is not exposed in the NTRS record; the citation here uses the conference venue only. AIAA-hosted PDFs returned HTTP 403 to ingest, so the abstract content cited below comes from the NTRS landing page.

Corroborating sources

Genova, A. L. (2016). Circumlunar Free-Return Cycler Orbits for a Manned Earth-Moon Space Station. NTRS 20160004674. · link
Companion / follow-up report from the same author covering the same orbit family.

Notes

Buzz Aldrin's lunar-cycler extension of his Earth-Mars cycler concept. Co-authored with NASA Ames trajectory analyst Anthony L. Genova. The orbit is "free-return" in the sense that any spacecraft flying on it will naturally return to Earth without propulsion; "modest phasing maneuvers" (average 39 m/s per month per the abstract) compensate for solar-gravity perturbations and keep the geometry repeating. Useful as a destination for crew transfer: per the abstract, lunar encounters "offer the chance for a smaller craft to depart the cycler and enter lunar orbit, or head for a Lagrange point (e.g., EM-L2 halo orbit), distant retrograde orbit (DRO), or interplanetary destination such as a near-Earth object (NEO) or Mars." MODEL NOTE: like the Arenstorf entry, this is best modelled in the Earth-Moon CR3BP with solar-perturbation third-body, not in patched-conic + V_infinity. The numerical signature fields are largely null and should not be used for M7 novelty matching against heliocentric finder hits.

Source quotes (per-field provenance)

Every numerical value in this entry traces to a verbatim or paraphrased quote from a cited source.

first_published.title: NTRS 20150018049 title: "A Free-Return Earth-Moon Cycler Orbit for an Interplanetary Cruise Ship" — Genova, Aldrin.
legs[0].tof_days: NTRS abstract: "introducing solar gravity and modest phasing maneuvers (average of 39 m/s per month) which yields close-Earth encounters every 7 or 10 days."
legs[1].tof_days: NTRS abstract: "Lunar encounters occur every 26 days and offer the chance for a smaller craft to depart the cycler and enter lunar orbit..."
notes: NTRS abstract: "introducing solar gravity and modest phasing maneuvers (average of 39 m/s per month)" (delta-V budget cited in notes).