Usually simply abbreviated as a RUD, and also sometimes expanded as Rapid Unplanned Disassembly, and being a way of understating that a rocket exploded.

I saw it attributed recently to Elon Musk, but although he has popularized the phrase among the public, when he mentioned it once in a speech I saw he simply said it is how the engineers on the SpaceX team like to refer to such an event.

So what is the history of this phrase, and can it be traced back to the person who came up with it?

  • 7
    I don't know for sure, but it would predate Elon Musk's cosmic entrepreneurship or even Kerbal Space Program that most of web searches would suggest. I remember it as rapid unscheduled disassembly, but there are other variants (hard start is used for overpressure during ignition, which is also subtly funny). I wouldn't be surprised if these go as far back as von Braun's or even Goddard's times of rocketry. When you have so many spectacular failures (i.e. "kaputniks") before you finally succeed, you either find comfort in humor or go insane. – TildalWave Jul 18 '15 at 19:06
  • 2
    Here's an article from 1991 edition of Cruising World using this term. So it would be used long before that and a common engineering term by then, I can't imagine how it would be coined for the purpose of describing torn boat sails. – TildalWave Jul 18 '15 at 19:22
  • 7
    It was in use when I started my aerospace career in the early 80s. – Organic Marble Jul 18 '15 at 21:31
  • 2
    I was going to say that it is at least 20 years old, but @OrganicMarble wins. "Unscheduled" is the proper expansion. – Mark Adler Jul 19 '15 at 4:35
  • 6
    I asked David S.F. Portree, a spaceflight historian and since recently also a Space Exploration SE denizen, and he thinks it might have been used when an S-IVB stage ruptured on an MSFC test stand c. 1965, and that it would reference a specific event. I tend to agree, it could be related to the Saturn 503 S-IVB explosion at the Douglas Sacramento, CA and subsequent MSFC-appointed investigating board's Disassembly Activities (chaired by Kurt Debus, KSC) in 1967. – TildalWave Jul 19 '15 at 4:46
up vote 39 down vote accepted

So far as I can tell, it was first a saying used by military personnel as the phrase "Rapid Unintentional Disassembly", for a phrase when a gun broke apart if you misused it. This was used by a book for Navy Personel in 1970, so I suspect it was in use for a while before then. This seems to have evolved from that phrase somewhat over the years. The earliest I can find it in rocketry specifically was the book entitled "Rocket Religion", copyright 2002, again with the same phrasing.

It seems to have exploded in popularity around 2011. I can't tell the exact source, but it was either Elon Musk or Kerbal Space Program, most likely.

  • 1
    By "gun" do you mean rifle or artillery piece? – Jerard Puckett Jun 16 '16 at 1:18
  • 1
    The chapter is entitled "Small arms and Machine Guns", so something smaller than artillery. Unfortunately I don't have access to more of the book... – PearsonArtPhoto Jun 16 '16 at 1:19
  • I love that Musk and KSP are equally as likely to have migrated this to rocketry. :) – jklemmack Sep 18 '17 at 16:33
  • 2
    My impression is that KSP is more responsible for "lithobraking" while Musk popularized "RUD". – lamont Dec 8 '17 at 19:47

Here's a reference from 1967 in "The MAC Flyer", Volume 14, Issue 5. This appears to be a periodical of the US Military Airlift Command. I have not been able to locate full text (but would certainly appreciate updates).

... an interface with hazardous conditions which could preface an unscheduled disassembly, ...

There is a number of expressions which convey much the same meaning. And it is hard, if not impossible, to find the originator.

The expression I heard first was 'spontaneous rapid disassembly event' which according to New Scientist Feedback column (July 2004) is used to describe explosions in scientific papers.

Other expressions

  • Fire : uncontrolled thermal event
  • Bursting : unplanned loss of containment
  • Crash : deconstructive deceleration
  • 4
    Worth adding to the list of expressions: Lithobraking maneuver. – SF. Sep 16 '17 at 15:14
  • 1
    @SF. "Unplanned catastrophic lithobraking maneuver" ? – jklemmack Sep 18 '17 at 16:38
  • 1
    @jklemmack: "The engines failed to shut down, sending the probe into lithobraking trajectory." "The orbit goes below peaks of tallest mountains, creating a lithobraking risk." – SF. Sep 18 '17 at 16:59
  • 2
    It can be also phrased as "negative periapsis altitude orbit." – SF. Sep 18 '17 at 17:13
  • 1
    Ah - so on the LEFT-hand side of @Tarjei Jensen's list :) – jklemmack Sep 18 '17 at 17:14

I thought that I saw the term used while reading about the early history of JPL many years ago but I can't find the article now. I do see that that JPL started in the 1930's:, so maybe researching old archives from JPL in those years could turn something up.

I did find this: where on p.42 it states, "I deemed it “pre-unplanned disassembly” at the time." (Gerald R. “Jerry” Pfeifer?) It's not 100% clear when "the time" was but it seems to be early 1960's and the way he says it makes it sound like it was his own phrase. Same paper p.48 he says, "managed to cause another unscheduled disassembly of the facility" but it's not clear if that was the term he used at the time of the disassembly many years ago or just while giving the lecture about that time (2006). If he's still around maybe someone should ask him before it's lost knowledge.

  • That is a great book you've linked to, i will definitely be reading it all. That passage is good circumstantial evidence, but i agree the only way to settle this is to root through archives and ask people who were involved and are still with us. – kim holder Feb 20 at 17:43

The acronym was in use in Navy F-14 squadrons in the mid-70’s. The Pratt & Whitney TF30-P-414A engines had an unfortunate habit of shedding blades. The repairs, which involved really tedious and carefully sequenced tear down and inspections, were occasionally followed by engines failing and shredding themselves during full-power post-assembly tests. I remember an Engine Chief explaining that he preferred “rapid unplanned disassembly” to the other kind when the engine “was a lemon”. (I’ve omitted some chiefly adjectives)

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.