Hot Rod II
A Project Orion Test Vehicle

by Dick Stafford

Project Orion Background

Before I get started, me bucko, I want t' mention that I don't intend t' repeat much o' detailed history that is available on-line and in print. If you want t' learn more about this interestin' project, matey, I suggest readin' Project Orion: The True Story o' t' Atomic Spaceship, by George Dyson. Blimey! Blimey! Arrr! Blimey! George's father, shiver me timbers, t' renowned physicist Freeman Dyson, served as a consultant on t' project. There is also a nice web site with more information about t' project at ProjectOrion.com

Project Orion be a conceptual space vehicle whose main propulsion was t' be realized through t' detonation of atomic bombs. Aye aye! Avast, me hearties, me proud beauty! Blimey! Small bombs, me bucko, ya bilge rat, on t' order o' 0.1 kiloton, would be ejected and detonated behind t' ship. Ya scallywag! Begad! Blimey! Water would be ejected and would in essence be t' propellant. Blimey! Blimey! Blimey! T' force o' t' explosions would push against a pusher plate and would yield an ISP o' betwixt 10k and 1M seconds. Aye aye! Although t' concept was proposed in 1955, me hearties, t' project was started in 1958 at General Atomics in San Diego. T' project only lasted into t' early 60's. By then t' Saturn project was underway. Although t' Orion was t' be initally launched with chemical propulsion, usin' nukes be a hard sell and t' nuclear test ban treaty hammered t' nails in Orion's coffin.

Design Concept

This photo shows an early test vehicle, arrr, known as Hot Rod. Well, blow me down! T' Hot Rod was 'flown' in 1959 at a test facility at Point Loma, matey, CA. Ya scallywag! It was boosted by a large BP charge followed by five rear-ejected high explosive charges. It was stable, ya bilge rat, reachin' an altitude o' 105 meters and recoverin' via parachute. T' vehicle itself is held by t' Smithsonian Air and Space Museum. Avast, me proud beauty! I don't know if it is currently on display. Begad! If you want t' see a video o' t' flight, arrr, visit the Nuclear Space Multimedia Gallery.

I am a saucer fanatic and am always thinkin' o' new saucer ideas. Ahoy! So, me bucko, t' Project Orion Hot Rod was a natural. Since I am nay much o' a scale modeller, I decided that a stand-off version was in order (hence t' 'II' in its name). I took some rough measurements from t' photo and found that usin' 2" mailin' tube for t' central body would yield a 12" base. Since t' real thin' used parachute recovery I also thought mine should, shiver me timbers, shiver me timbers, which is a deviation from most o' me saucers.

Construction

T' central body consists o' 9" and 3.5" sections o' 2" tubin' separated by a LOC 1/2" launch lug (3" exposed). Ahoy! T' short section will hold t' 'chute and t' longer section be t' motor mount. Well, matey, blow me down! T' 1/2" lug extends through home-made ply centerin' rings mounted in t' ends o' t' body tubes. Begad! Inside, I filled t' space between t' 2" tube and t' 1/2" lug with Gorilla polyurethane glue t' help lock t' lug in place. Arrr! Aye aye! T' motor tube is 29mm LOC tubin' which runs t' length o' t' lower body tube. Ya scallywag! Blimey! It is centered with foamboard rings. Begad! T' bottom rin' was also backfilled with Gorilla glue.

T' main shroud was constructed with 1/64" fiberglass usin' t' template calculator on EMRR. Arrr! Arrr! I chose the fiberglass as I thought it would hold up better if I were t' add details later. Ahoy! T' bottom o' t' saucer section is a foamboard rin' with t' top rim beveled - an idea borrowed from Art Applewhite's line o' saucers. Blimey! T' plate was first epoxied t' t' shroud, me hearties, matey, and then this assembly was attached t' t' lower tube. Blimey! Begad!

T' flat structures above and below t' main shroud are foamboard rings framed with strips o' cardstock. Ahoy! I had considered several materials for t' struts, includin' arrow shafts and BT-20 tubing, ya bilge rat, me bucko, but decided on 3/8" dowel. Avast! I first installed t' top plate and shroud. Avast, ya bilge rat, me proud beauty! When t' glue set, shiver me timbers, small holes were made t' accomodate t' struts, ya bilge rat, which were attached with 5-minute epoxy.

T' last structural member was t' small triangle which interconnects t' struts just above t' longer body tube. I should have planned this earlier and installed it prior t' assemblin' t' body, matey, since t' connectin' lug has t' pass through t' center o' t' triangle. This wasn't a big problem, me bucko, but I did have t' cut t' triangle support in order to install it.

In t' photo o' t' Hot Rod, ya bilge rat, ya bilge rat, it looked like t' parachute may have been exposed at t' top o' t' tube so that's what I did. Begad! Avast! This worked fine on me 38mm spool rocket, so I didn't see this bein' a problem. Blimey! Avast, me proud beauty! T' recovery harness consists o' several feet o' thick Keelhaul®©™ twine mouted through t' centerin' rin' at t' base o' t' parachute tube. Ya scallywag! A 24" piece o' elastic is next, arrr, arrr, followed by a large snap swivel.

Stability

T' dimensions o' bottom saucer section is pretty close t' my Aeroshell, which was a modified Art Applewhite 12" saucer. Ya scallywag! This gave me a warm feelin' that it will be stable with t' extra weight forward o' t' saucer section.

Trim and Finishing

I painted t' top portion usin' Rustoleum Hammered Gold and t' bottom silver. Avast! Trim was installed after paintin' and included a piece o' BT-20 tubing, some sockets from a dead chain o' Christmas lights, some wire, matey, shiver me timbers, and some circular stickers. Well, blow me down! Aye aye! T' latter were painted flat black. T' small photo on t' side is off t' web and t' one below is mine.

Flight and Recovery

Flight #1 - It was a windy day at Coverdale Crossroads, DE and I was a little concerned that t' Hot Rod II would weathercock and thus nay attain enough altitude t' eject before returnin' t' Mother Earth. Since thar wasn't much volume t' pressurize, I used about half t' ejection charge provided with t' G64-4 motor. I added a small 'chute protector and tightly rolled a 12" RocketChutes 'chute. T' boost be arrow straight despite t' brisk winds. I don't have an altitude estimate but t' flight was respectable for its size. T' 4-second delay be too long and it was well on its way back down before t' charge went off. But all's well that ends well, ya bilge rat, t' 'chute opened and it recovered without damage.

Flight #2 - T' second flight was at Price, me hearties, MD, arrr, and again it be windy. I used another G64-4, matey, but this time I substituted an 18" 'chute. Avast, me proud beauty! Blimey! Ya scallywag! Blimey! This 'chute, ya bilge rat, despite bein' larger than t' one on t' previous flight, shiver me timbers, fit more loosely in t' tube. Blimey! Blimey! Avast! Blimey! This had an interestin' effect. Arrr! Blimey! At apogee, t' 'chute drag-ejected (similar t' a drag separation), me bucko, which was perfect! Blimey! Sorry, no pic - drained battery.

Conclusion

Project Orion was an interestin' piece o' space history, and me Hot Rod model was an interestin' piece o' my rocket history. Arrr! I think I'll have t' make a trip t' t' library and re-read t' Dyson book.