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Author
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Topic: Who first thought of gravity assists?
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Blackarrow
Member Posts: 3120
From: Belfast, United Kingdom
Registered: Feb 2002
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posted 06-27-2019 02:59 PM
  
In 1997, during 20th anniversary Voyager celebrations at JPL, a question was asked at a table-quiz: Who first articulated "Detour Trajectory" otherwise known as gravity-assist trajectories, as used by Voyagers 1 and 2?The answer given (Gary Flandro) was ruled to be incorrect. The official answer was Michael Minovitch, in the 1960s. (See Jay Gallentine's "Ambassadors From Earth.") I suppose much depends on the definition of "articulated" and I'm not getting into that debate. However, I draw attention to the following published passage: You see, if we can leave next year we can go past Jupiter on the way and have our first really good look at him. Mac's worked out a very interesting orbit for us. We go rather close to Jupiter - right inside ALL the satellites - and let his gravitational field swing us round so we head out in the right direction for Saturn. It'll need rather accurate navigation to give us just the orbit we want, but it can be done. This is from "The Sands of Mars" by Arthur C. Clarke, first published in 1951. |
Headshot
Member Posts: 864
From: Vancouver, WA, USA
Registered: Feb 2012
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posted 06-28-2019 10:53 AM
A colloquium describing potential use of gravitational assists for upcoming space missions (Pioneers F & G, Mercury-Venus 1973, and the proposed 1978 Grand Tour) was given by a graduate student at the University of Illinois in May of 1970. So it had to be earlier than then. |
Headshot
Member Posts: 864
From: Vancouver, WA, USA
Registered: Feb 2012
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posted 07-03-2019 11:12 AM
On a theoretical/mathematical level, papers were published in the 1920s and 1930s suggesting Gravity Assists were possible.Gravity assist techniques were used by the Soviets in 1959 during the Luna 3 mission and by the United States for the Mariner 10 Venus-Mercury Mission in 1973-1974 and to sling Pioneer 11 towards Saturn in late 1974. Check out the Wikipedia entry for Gravity assist. One item of which people might not be aware is that while gravity assists can speed spacecraft up,doing so slows the planet down. This is the law of conservation of angular momentum. A 10,000kg getting the maximum assist from Jupiter will shrink Jupiter's orbit by 10 to the minus twelfth Angstroms. A change that can be calculated, but not measured. |
Blackarrow
Member Posts: 3120
From: Belfast, United Kingdom
Registered: Feb 2002
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posted 07-06-2019 09:18 AM
You can probably go back as far as Kepler in the early 17th century. Once he had established that all of the planets orbited the sun in elliptical orbits which result in a planet moving faster at its closest point to the sun and slower at its most distant point, the general principles governing gravity assist had been established.But actually describing the practical use of planetary assist techniques, in a mission to Saturn via Jupiter? To foreshadow the mission profiles of Pioneer 11, Mariner 10 and the Voyagers by over two decades? However, I have remembered an even earlier example of the trajectory of a spacecraft being altered by a close encounter with another body in space. "Round the Moon" by Jules Verne was published in 1870. The projectile containing three explorers was fired into space from Florida by a huge cannon (named "Columbiad") on a remarkably precise trajectory, but shortly after "launch" the projectile passes close to a small previously-unknown asteroid which has been captured by the Earth's gravity. The close encounter perturbs the projectile's trajectory, with the result that it fails to reach the Moon, but passes around it in something similar to the "non-free-return" trajectories of the later Apollo missions. One of the explorers then has the idea of using the rocket-jets which should have cushioned their landing on the Moon to steer them back to the Moon, but this actually (and fortunately!) places them on a "free-return trajectory" back to Earth, 100 years before Apollo 13's LM engine does the same thing for three 20th century explorers. I think it unlikely that literature contains any earlier example of a spacecraft's trajectory being altered by a close encounter with a planetary body, but don't let that stop someone proving me wrong! |
Jonnyed
Member Posts: 396
From: Dumfries, VA, USA
Registered: Aug 2014
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posted 07-07-2019 08:06 PM
Jules Verne was amazingly before his time. Your example of gravity assist in his novel is fascinating. Also think of the description that he gives the propulsion plant of his ship Nautilus in "20,000 Leagues Under The Sea"... sounds pretty much like a nuclear power plant. Great stuff, decades ahead. | |
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