Gravity assist

Assembled from 14 blocks · 2 evidence · 30 related

1. Story
2. The manoeuvre that lets a spacecraft gain speed relative to the Sun without burning fuel, by passing close to a moving planet. In the planet's own frame the spacecraft arrives and leaves at the same speed, merely turned through an angle; in the Sun's frame that turn adds the planet's orbital velocity vector to the spacecraft's, and the spacecraft leaves faster. Momentum is conserved because the planet is slowed by an exactly compensating amount — an amount so small against Jupiter's mass that it is unmeasurable. The technique was worked out in the early 1960s, notably by Michael Minovitch, and applied at Venus by Mariner 10 before Voyager used it four times in sequence. It is what made an outer-planet tour affordable: reaching Neptune directly with a 1970s launch vehicle would have taken about thirty years, and Voyager 2 did it in twelve. Not a place.
3. Knowledge
4. Gravity assist
5. Connections
6. Voyager 1
7. Voyager 2
8. Flandro identifies a four-planet gravity-assist opportunity
9. The Grand Tour alignment
10. Voyager 1 closest approach to Jupiter
11. Voyager 2 passes Saturn and continues towards Uranus
12. Evidence
13. The late-1970s alignment of Jupiter, Saturn, Uranus and Neptune permits a single spacecraft to reach all four by successive gravity assists, an opportunity recurring only on a timescale of roughly 175 to 176 years. V55 verification basis: NOT CHECKED IN THIS RUN. The title, journal, volume and year are given from standard citation practice and the search budget was exhausted before they could be confirmed; the 175 versus 176 year figure differs between accounts and is deliberately given as a range. A curator must verify this citation before publication.
14. The canonical mission record for both spacecraft: launch dates of 20 August 1977 (Voyager 2) and 5 September 1977 (Voyager 1), the Titan IIIE-Centaur launch vehicle, Launch Complex 41 at Cape Canaveral, the eleven-instrument science payload and the three-generator power system. V55 verification basis: THE CATALOGUE WAS NOT REACHED. nssdc.gsfc.nasa.gov returned EGRESS_BLOCKED when fetched and the search budget was exhausted before it could be searched; the COSPAR designations and every fact attributed here come from standard mission record held in general knowledge, not from the catalogue. This record names where a curator should check, not what was checked.