Jon: This is an old sketch of the jig for the domes for the 1994 rocket design. They were formed at 4500 psi with water forming 1/8" thick 6061 T6 aluminum at room temperature. Each cycle was a few sec duration with manual control of water pressure. I found 4500 psi made the domes just under 1 inch deep, and results were consistent from dome to dome. Made about 30 total./ With 1/16", less than 1000 psi made a dome less deep, before getting the high pressure pump. I accidentally blew one at 7500 psi by not watching the pressure build-up and opening a relief valve quickly enough. Result was conical, with a torn opening at the jig opening. With a test square of aluminum with 1/2" grid painted on, the dome showed very even stretching. A friend made a thin dome 22 inch dia and used air at 120 psi. This method works well, the 5 min time for each being mainly that to undo bolts and install another 5" square of aluminum. No explosives needed. Works so well I plan this for the 8" or 10" domes for Microlaunchers. Charles Pooley ________________________________ From: Jonathan Goff <jongoff@xxxxxxxxx> To: arocket@xxxxxxxxxxxxx Sent: Monday, September 16, 2013 9:36 AM Subject: [AR] Re: Explosive Hydroforming (was Re: Re: F9 Engine Incident) Charles, I was looking at I think 30-48in hemispherical domes about .25" thick. Normal hydroforming might have done it, but a full hemi dome without tearing is non-trivial. The nice thing about explosive hydroforming is that if done right, the material behaves differently when you deform it really quickly than when you do it slowly. ~Jon On Mon, Sep 16, 2013 at 10:28 AM, Charles Pooley <ckpooley@xxxxxxxxxxxxx> wrote: For Jon: No explosives needed for simple domes. A 1994 rocket I designed for a project used 4 inch diameter domes for a 4 inch irrigation tube tank rocket. It was done with a jig and water pressure, with room temperature 6061 T6 aluminum. They were consistent 0.95 inch deep and required no heat treating or anything after. > >Charles Pooley > > > > > > >________________________________ > From: Jonathan Goff <jongoff@xxxxxxxxx> >To: arocket@xxxxxxxxxxxxx >Sent: Monday, September 16, 2013 9:22 AM >Subject: [AR] Explosive Hydroforming (was Re: Re: F9 Engine Incident) > > > >Carlo, > >I was looking into explosive hydroforming back when I was at Masten. One of >the documents I was reading had a picture of a submarine nose cone that they >had formed using the process. IIRC it was over 20ft wide, over 4-6" thick, and >made of a high-strength submarine steel alloy (a maraging steel alloy I >think). Pretty fun process. I had been thinking of using it to try and form >tank heads out of some high-strength aluminum alloys that don't spin well >(6013 Aluminum and stuff like that), but we ended up dropping that for some >reason or other in favor of a more traditional spun 5059 tank approach. > >~Jon > > > >Note: decided to change the thread name since there doesn't seem to be >anything in the current thread related to the original thread title... > > > > >On Sun, Sep 15, 2013 at 4:35 PM, Carlo Vaccari <airplaniac2002@xxxxxxxxx> >wrote: > >I've heard of explosive welding, but not forming, at least until reading about >the Merlin 1D. I guess it's better than simple hydroforming for thin shells >which perhaps can balloon? >> >> >>Checking the Wikipedia page on it says that the SR-71 chines and various >>Russian rocket parts are formed this way... >> >> >> >> >>On Sun, Sep 15, 2013 at 6:23 PM, David Weinshenker <daze39@xxxxxxxxxxxxx> >>wrote: >> >>Krishna Kattula wrote at 06/21/2013 10:55 PM: >>> >>>> Ben Brockert wrote: >>> >>>>> Where did they say they were using a new process for the 1D? There >>>>> were rumors of them trying a modern approach to the tube bundle >>>>> concept, but I haven't seen any evidence that they're pursuing it for >>>>> the current engines. 1D seems to be an evolutionary step. >>>>> It's almost definitely not printed, no one has done DMLS-type >>>>> processes at that scale. >>>>> Ben >>> >>>> Explosive forming apparently: >>>> http://spacenews.com/profiles/110425-elon-musk.html >>>> ".... >>>> The hardest part of the engine to mass produce is the electro-plating of >>>> nickel cobalt on the chamber. We create this thick metal jacket that takes >>>> the primary stress of the pressure vessel and it's plated one molecule at a >>>> time. Plating is about the slowest way you can make a metal thing. With the >>>> Merlin-1D we take a metal jacket that is explosively formed. We take a >>>> metal >>>> sheet that's in a cylindrical form and put it in a bucket of water, >>>> effectively. Sort of a concrete pool. And you set off an explosive and the >>>> jacket just goes "boohmp" and forms to the outer side walls into a jacket >>>> shape, so you have a mold, effectively. And then you just put the jacket on >>>> the chamber and braise it on. You can do several a day. We have a fully >>>> integrated engine and it's being test-fired right now. There's really not a >>>> lot of question marks remaining about the Merlin-1D. >>>> ..." >>> >>>Pretty clever - the R+D work to make that a >>>repeatable process must have been interesting! >>> >>>-dave w >>> >>> >> > > >
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