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"I don't have an e-mail address. As much as I admire the Internet I suffer literally agoraphobia, which in it's original sense means a fear of the marketplace. I do not want to receive three hundred e-mail messages per week from strangers…"
- William Gibson
 |
| Gravity Assist | ||
| Using the gravity and orbital speed of a celestial body to change speed and course of a spacecraft. |
These "manoeuvres" were an essential part of the earliest visits to the outer solar system.
In the book, an Earth spaceship by Martian brigands who are determined to get their hands on the Moon's one key resource, radiactum. Radiactum was "the catalyst mineral which was revolutionising industry."
| We were at this time no more than some sixty-five thousand miles from the moon's surface. The Planetara presently would swing upon her direct course for Mars. There was nothing that would cause passenger comment in this close passing of the moon; normally we used the satellite's attraction to give us additional starting speed. |
| From Brigands of the Moon,
by Ray Cummings. Published by Astounding Stories of Super Science in 1930 Additional resources -
|
The mathematics of the manner in which the orbits of comets were altered by close approaches to planets was known in the late eighteenth century. However, this idea was not applied to space craft until much later.
In the early nineteen-twenties, Walter Hohmann demonstrated that the lowest energy path between any two planets is an ellipse that is tangential to the orbits of both the planets. However, no rockets existed until the 1960's that were powerful enough to generate the initial thrust, and a minimum energy orbit would take thirty years from Earth to Neptune - and forty years to Pluto.
In the volume published in 1932, Nikolai Alexyevich Rynin introduced the reader to the mysterious Yuri Vasilievich Kondratyuk. In a volume of Interplanetary Flight published in Russian in 1932, this description of gravity assisted flight was included:
A historical review of the theory of gravity‑assists
in the pre‑spacefight era
It's not clear whether or not this published work was related to earlier, unpublished work by the author dating back as far as 1920.
To the best of my knowledge, the concept of "gravity assist" as a means of altering the speed or course of a spacecraft was apparently not discovered by the scientific world (in English, anyway) until some 20 years after the publication of Cummings' novel. In a footnote A C Clarke indicates the first ref he's aware of was the paper "Perturbation Manoeuvres" by Derek Lawden (Journal of the British Interplanetary Society, vol 13, no 5, Sept 1954). Lawden is a mathematician, and in the early fifties worked on the optimization of rocket trajectories. It is also reported that a summer intern at JPL in 1961, Michael A. Minovitch, showed that the gravity field of a planet could provide thrust to a spacecraft. He demonstrated that careful design of the trajectory to a target planet could provide a gravity assist to move from that planet to a second planet.
Historians of science still differ on this issue.
Thanks to an alert reader for this item!
Kondratyuk laid in two paragraphs a vague
concept of gravity-assist. In the first paragraph,
he suggested that a close approach between the spacecraft
and the satellite of a planet may be used to “gather velocity” for a solar system journey and to “absorb velocity”
when it is returning. In the second paragraph, a figure
similar to Fig. 2 was used to explain that two approaching bodies may be used to continuously increase the velocity of a vehicle describing a trajectory around them. He
correctly remembered that the vehicle will lose velocity
if the bodies are moving apart.
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Additional
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More Ideas
and Technology from Brigands of the Moon
More Ideas
and Technology by Ray Cummings
Tech news articles related to Brigands of the Moon
Tech news articles related to works by Ray Cummings
Gravity Assist-related
news articles:
- Gravity Assist Will Help Pluto-Bound Craft
- The Amazing Gravity-Assisted Journey Of Rosetta
| Changesite Mineral To Be Mined On Moon By China |
| Taikonaut Tai Chi Foot Loops |
| Space Billboards Would Ruin Our View Of The Cosmos |
| Orion's 'Skip-to-M'Lou' Entry |
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'The pokkecon rang again. *The coffee’s for him?* Tsuyoshi said.'
The Jetsons imagined so much future.
'Rod placed the brain inside the panel... the horse raised its head, wiggled its ears, blinked twice, gave a tentative whinny.'
'Pina2bo would have to operate full blast for many years to put as much SO2 into the stratosphere as its namesake had done in a few minutes.'
'Chain of hotels that specialized in non-human service.'
'But then... not every bulldozer operator works on the Moon.'
'Griff found the white and pink map distracting and switched it off using his tongue mouse.'
