Tito 2018 manned Mars free-return (one-window E-M-E ballistic flyby)

tito-2018-mars-free-return · source: literature · validation: V0

Signature

Bodies: E-M
Primary: Sun (default — heliocentric)
Sequence (canonical): E-M-E
Sense: n/a
Orbit class: Tour
MGA tour (one-shot terminal arrival)
Cycler class: multi-arc
Returns: 1 — finite for epoch-locked classes
Validity window: 2018-01-05 → 2019-05-21
Launch epoch: 2018-01-05T07:00:00Z
Trajectory regime: ballistic
Maintenance ΔV band: unclassified
Model assumption: analytic-ephemeris
Mid-fidelity: real eccentricity / inclination retained; not full N-body.
Period: not strictly periodic (no published period)
Source ephemeris: DE421
Ephemeris model the source states its numbers were computed against.
Priority date: 2013-01-01

V∞ at encounters

E (encounter 1): 6.23 km/s
Tito 2013 Tables IV leg-1 Earth departure V_inf; ours 6.226 km/s on DE440 (-0.09%; -0.17% on C3).
M (encounter 2): 5.42 km/s
Tito 2013 Tables IV Mars flyby (in ≈ out at 5.417 km/s); ours 5.424 km/s in / 5.413 km/s out on DE440 (+0.13% / -0.07%); ballistic continuity confirmed (required bend 33.4 deg vs cone 34.2 deg at 100 km periapsis).
E (encounter 3): 8.84 km/s
Tito 2013 Tables IV leg-2 Earth arrival V_inf; ours 8.900 km/s on DE440 (+0.71%; +1.42% on C3; the larger residual is the DE421->DE440 ephemeris difference accumulated over 274 d).

Cycle-level identity (multi-arc invariants)

Aphelion ratio (AR): —
Turn ratio (TR): —
Transit times (days): —

Orbit view 2.5D ecliptic projection

spacecraft: analytic-ephemeris (real e/i retained) planets: J2000 osculating ellipse (Standish & Williams Table 1) orientation: coplanar-idealized (no Ω/ω published — in-plane ellipse)

3D view not available for multi-arc trajectories yet. The 3D system can now render a numerically-sampled polyline (n-body or multi-arc), but no sampled trajectory is published for this row — each leg is a separate ellipse with honest gaps where elements are unpublished (the 2D view above shows them). The button will appear here once a sampled path is exported for this trajectory; we never interpolate one from the catalogue's per-leg (a, e).

— — planet orbit (true J2000 ellipse)

Definition status

incomplete — core fields missing or known-unknowns tracked below

Primary citation

Tito, D. A. et al. (2013). Feasibility Analysis for a Manned Mars Free-Return Mission in 2018. IEEE Aerospace Conference, 2013.

orbit source derived orbit fidelity analytic-ephemeris V∞ source derived V∞ fidelity analytic-ephemeris

Corroborating sources

Luidens, R. W. (1964). Mars Nonstop Round-Trip Trajectories. AIAA Journal, Vol. 2, No. 2, pp. 368-370 (1964).
(2026-06-19): the earliest sourced Earth-Mars-Earth ballistic free-return analysis in the corpus (21 yr before the Aldrin cycler, 49 yr before Tito 2018). Luidens compares gravity-only / propulsive-gravity / aerodynamic turn classes for 1971 + 1980 launches; Tito 2018 is structurally an ephemeris-locked instance of Luidens's near-pure-gravity-turn free-return class. See docs/notes/2026-06-17-digest-luidens-1964.md.

Notes

Single Earth-Mars-Earth ballistic free-return for the once-per-~15-yr fast opportunity at the January-2018 launch window. 501.3-day total. Single Mars gravity assist (~100 km periapsis altitude, ~7.27 km/s periapsis speed) drops perihelion toward Venus's orbit. Terminal Earth re-entry at 14.18 km/s; no next lap. Admitted under the catalogue scope expansion (2026-06-15) as orbit_class=mga_tour; was withheld under the prior cyclers-only scope per project_catalogue_scope_cyclers_only memory and docs/notes/2026-06-13-tito-maccallum-2018-free-return-reproduction.md §4. Reproduction (DE440 vs Tito's published DE421): all four V_inf within 0.71% (departure C3 within 0.17%, arrival C3 within 1.42% — the return-arc residual is dominated by the DE421->DE440 ephemeris difference, not a model error); Mars-flyby ballistic continuity independently confirmed (33.4 deg required bend fits inside the 34.2 deg cone at the published 100 km periapsis). Reproduction notes: docs/notes/2026-06-13-tito-maccallum-2018-free-return-reproduction.md Reproduction script: scripts/tito_free_return_repro.py

Source quotes (per-field provenance)

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

validity_window.start: Tito 2013 Tables III: 'Depart Earth, 5 Jan 2018 07:00:00.000 UTCG'.
validity_window.end: Tito 2013 Tables III: 'Arrive Earth, 21 May 2019 13:52:48.012 UTCG'.
vinf_kms_at_encounters.0.vinf_kms: Tito 2013 Tables IV leg-1: 'Dep V-inf 6.232 km/s'.
vinf_kms_at_encounters.1.vinf_kms: Tito 2013 Tables IV leg-1 / leg-2: Mars arrival V-inf 5.417 km/s; Mars departure V-inf 5.417 km/s (ballistic free-return symmetry).
vinf_kms_at_encounters.2.vinf_kms: Tito 2013 Tables IV leg-2: 'Arr V-inf 8.837 km/s' (the entry-speed driver for the TPS analysis).