I've read in the past that the original Death Star prop was blown up for the movie scene. Today I came across this and was wondering if there was any truth to that rumor.
According to the description in the last page of this article (pdf), it doesn't sound like they blew up the prop itself, since they describe creating the effect by filming the explosion of a "cardboard container of black powder mixed with titanium shavings" against a black background.
He [special effects artist Joe Viskocil] reasoned that since there is no air and no gravity in space, the explosion should be perfectly spherical and not lopsided or squashed. To get a perfectly symmetric effect, he put the camera on the ground and filmed straight up.
A cardboard container of black powder mixed with titanium shavings was suspended from the studio’s ceiling. Black powder is a mixture of sulfur, potassium nitrate (kNo3), and charcoal—a black substance made mostly of carbon, along with other chemicals, and resulting from the heating of wood. When the black powder ignited, sparks and debris were propelled toward the camera as if travel- ling outward in the vacuum of space. The technique was so successful that it has been copied many times since then.
Looking on Google Books, I found a series of helpful snippets in this bundle of Cinefantastique issues (it says it includes volumes 5-7, googling around I see each volume was for a different year and those volumes 5-7 were from 1976, 1977 and 1978... my guess is that the snippet would be from their "Star Wars Special Double Issue", vol 6 #4 and vol 7 #1, published in 1978). If you plug any sentence or extended phrase from the following into a Google Books search you get that Cinefantastique collection:
All of the T.I.E. fighter explosions were double-exposed over the actual miniatures. Top Left: The climactic explosion of the Death Star filmed at Producer's Studio in Hollywood. Like the T.I.E. fighter explosions, this was also superimposed over the Death Star miniature. For this explosion Viskocil used a "Special Titan Blend," which leaves a gas- type of aura or glow as it dies away.
So, it seems they first filmed the explosion, then double-exposed it over the Death Star miniature. Also found this snippet from the same bundle addressing why they didn't blow up the actual prop (typos are left unedited):
Why were the T.I.E. fighter and Death Star explosions just double-exposed? Isn't it preferable to blow up actual models? It just seemed to work better with double- exposures in the case of the T.I.E. fighters, compared to the X and Y-wings. I think the T.I.E. fighters came out perfectly by double-exposing them. Richard Edlund wanted to blow-up the Death Star out in the ILM parking lot, and we discussed that. He wanted to use a crane, with the Death Star overhead, but it got down to time, and it got down to money, and we just couldn't doit." —Joe Viskoc
It certainly seems to be real. You can see the same prop in the photo below, which the one on display in Missouri matches perfectly.
That doesn't obviously mean that it's real (e.g. as opposed to merely being a very very convincing replica) but the lack of a debunking statement from LucasFilm who then offered to buy it and the interesting provenance lend a large amount of weight to the suggestion that the model was simply disposed of.
Ultimately it was purchased by Gus Lopez, the owner of the largest collection of SW memorabilia (outside of Skywalker Ranch) who's happy to vouch for its authenticity, along with the EMP Science Fiction Museum in Seattle who had the model on loan for nearly three years.
Since it exists, I think we can be fairly sure that they didn't blow it up.
The Death Star was blown up, Joe Viskocil told me so. I was Joe's girlfriend for nine years before he passed away last summer. I love Sci-fi and I was privileged to attend many comic conventions with Joe, see the making of several explosions and pick his brain about how it was all done.
The FX department created several models of the same ship at different scales, some are used to film different angles and the smaller model is usually used to create pyrotechnics effects, explosions that are filmed at about 300 frames per second so that when they show the explosion it's in slow motion (so we can enjoy the debris and the roar of the fire) The "selling shot" he use to call it, the shot they use in the trailer that sells the movie. Ka-Boom!
Joe Viskocil was very proud of his work in Star Wars. He was extremely disappointed that George Lucas added a ring to the original explosion when he re-released the DVD. We saw the movie together "The People vs. George Lucas"; so many changes in the DVD release, disappointing the hardcore fans that he changed most of it back to the original for the blu-ray.
Secrets of movie magic; if you watch "A New Hope", the hand that puts the message into C3PO is not Leia's but Joe Viskocil's hand . There is another shot of his hand a little later pushing buttons of the ship (close up).