The Story of Orion
How It Worked
Orion Drive > The Story of Orion > How It Worked
The basic idea for Project Orion is quite simple: can we use the blast from a nuclear bomb to generate thrust for a spacecraft?
The first idea that was considered, "Helios", was conceived by Freeman Dyson, who suggested exploding a small (0.1 kiloton) atomic bomb inside a combustion chamber approximately 40 meters (130 feet) in diameter. Water would be injected into the combustion chamber, superheated by the atomic blast, and then used for propulsion. The process would then be repeated, with each "pulse" from a subsequent atomic explosion adding to the vehicle's velocity. This idea was however problematic in that developing a combustion chamber that wasn't destroyed by the explosion would be a tremendous challenge. Furthermore the performance of Helios was relatively poor, only about 2½ times the specific impulse (that is the change in momentum per unit of propellant) of today's best chemical rockets.
The break-through can when Stanislaw Ulam realized that the nuclear explosion could only not be realistically contained, but that it did not need to be contained. Instead, nuclear bombs and reaction mass could simply be dropped out the back of the vehicle and exploded at some distance away, perhaps 60 meters (200 feet). The blast would generate a plasma wave which would impact a thick steel or aluminium pusher plate at the rear of the vehicle, causing the vehicle to move forward. Furthermore, it was possible to design the propellant units in such a way so that most of the energy from the bombs would be directed towards the pusher plate rather than in other directions.
Of course, the nuclear explosions would generate sudden shocks of massive acceleration (less than a millisecond duration) - this has been described as being hit by an atomic-powered sledgehammer. For a properly designed unmanned vehicle, these sudden accelerations are not necessarily a problem, but for a crewed vehicle, the acceleration needs to be smoothed out to a level that the crew could bear (1g to 3g) - and this would have done been using massive (multi-story high) pneumatic spring shock absorbers.
The other consideration is that of the survivability of the pusher plate, which is of course directly exposed to the plasma wave generated by the atomic blast. Many people would assume that any object close to a nuclear explosion could not survive - however this assumption turns out to be incorrect. Even though the plasma wave is tremendously hot, easily hot enough to vaporize steel or aluminium, the time of contact with the pusher plate is so brief that the metal can survive (the same principle is used in automobile engines) - indeed in the case of Orion, it turns out that a cooling system is not even necessary. Additionally, it was believed (due a chance discovery made during the atom bomb tests of the 1950s) that spraying the pusher plate with a few millimeters of graphite-based oil before each explosion would eliminate all ablation of the pusher plate.
The following chart shows figures for 3 different Orion designs:
In the final period of research on Project Orion, an alternative to ground-based launch was considered: assembling a very small Orion vehicle in Earth orbit, using 2 or 3 Saturn V launches. Although less efficient, by far, than the ground launched variants, this design would have completed avoided the issue of fallout. Despite its limitations, the vehicle would have been capable of taking 8 people to Mars and back in a voyage that would have lasted about a year.
Project Orion was of course never built, despite all the tests and research indicating that it was not only possible, but also feasible and affordable too. However a 1 meter (3 feet) model weighing 105 kilograms (231 pounds) was built, and successfully demonstrated.
Copyright © 2008-2024, Answers 2000 Limited
CERTAIN CONTENT THAT APPEARS ON THIS SITE COMES FROM AMAZON SERVICES LLC. THIS CONTENT IS PROVIDED 'AS IS' AND IS SUBJECT TO CHANGE OR REMOVAL AT ANY TIME.
CERTAIN CONTENT THAT APPEARS ON THIS SITE,COMES FROM AMAZON EU S.à r.l. THIS CONTENT IS PROVIDED 'AS IS' AND IS SUBJECT TO CHANGE OR REMOVAL AT ANY TIME.
Disclosure: Our company's websites' content (including this website's content) includes advertisements for our own company's websites, products, and services, and for other organization's websites, products, and services. In the case of links to other organization's websites, our company may receive a payment, (1) if you purchase products or services, or (2) if you sign-up for third party offers, after following links from this website. Unless specifically otherwise stated, information about other organization's products and services, is based on information provided by that organization, the product/service vendor, and/or publicly available information - and should not be taken to mean that we have used the product/service in question. Additionally, our company's websites contain some adverts which we are paid to display, but whose content is not selected by us, such as Google AdSense ads. For more detailed information, please see Advertising/Endorsements Disclosures
Click privacy for information about our company's privacy, data collection and data retention policies, and your rights.
In Association With Amazon.com
Answers 2000 Limited is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.
In Association With Amazon.co.uk
Answers 2000 Limited is a participant in the Amazon EU Associates Programme, an affiliate advertising programme designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.co.uk.
As an Amazon Associate, our company earns from qualifying purchases. Amazon, the Amazon logo, Endless, and the Endless logo are trademarks of Amazon.com, Inc. or its affiliates.
All trademarks are property of their respective owners.
All third party content and adverts are copyright of their respective owners.