What is the difference between the terms detach, jettison, and dump?

Related Aviation.SE question: https://aviation.stackexchange.com/q/22903

Examples of using the term "detach":

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    $\begingroup$ The aviation.SE question seems to have be definitively and clearly answered years ago, despite the answers not having been accepted. Can you provide a context for the use of "detach"? It's extremely hard to make nuanced distinctions between related terms without context. $\endgroup$ Jun 20, 2019 at 3:23
  • $\begingroup$ I think the difference is the context. $\endgroup$ Jun 20, 2019 at 16:35

2 Answers 2


As the Aviation.SE answers suggest, the distinction between a jettison and a dump is that dump refers to release of uncontained liquid (examples: a fuel dump, a wastewater dump) while a jettison is a release of a solid object -- maybe an empty fuel tank; historically, jettison was a nautical term meaning "a voluntary sacrifice of cargo to lighten a ship's load in time of distress", but in spaceflight a jettison is usually a planned action.

Both dump and jettison connote that the released item is not particularly useful or valuable. One might recover a jettisoned fuel tank for reuse, or observe the behavior of a dumped fluid, but those aren't part of the primary function of the vehicle.

In contrast, detach, to me, suggests that the detached item may have an ongoing function after detachment, and/or that it may be reattached at a point in the future. The Hayabusa detachable camera takes photos after detachment, serving a useful active function, rather than being an inert object. The Mercury heat shield doesn't actually leave the spacecraft, so "detached" is arguably the wrong term; it's released from its normal position, but still connected via the landing bag.

As with all natural language, these terms are a little fuzzy, as are the categories of things they refer to, so it wouldn't be surprising to see them applied in other ways.


Broadly speaking, "detaching" is the act of unfastening something, whereas "jettisoning" is to send away a thing. You have to detach something in order to jettison it.

The general distinction between "jettisoning" and "dumping" as described at Aviation holds up pretty well in the Space Exploration context, I think.

For clarity, "jettisoning" a fuel tank would be to send away the tank itself, and "dumping" a fuel tank would be emptying the fuel without sending away the tank.


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