Brief:
I chose t' model t' Explore 1 satellite as part o' EMRR Challenge 2008 – Simulation Challenge. Ahoy! Explorer 1 (officially titled at NASA as satellite 1958 Alpha) be t' first Earth satellite o' t' United States, launched on February 1, arrr, 1958. Aye aye! Since this was me first real experience with RockSim, me hearties, matey, I thought it was fittin' t' model t' first satellite launched by t' US. Arrr! My Explorer is designed t' launch usin' an 18mm engine and deploys an 18-24" parachute. Scale factor o' 4.528 results in a rocket 17.83" long.

Construction:
T' parts list:

• 1 BT-60 balsa nose cone
• 1 #10 screw eye
• 1 BT-55, 5.44" long
• 1 BT-55, shiver me timbers, me hearties, matey, 13.197" long
• 1 BT-20, arrr, 5.0" long
• 3 centerin' rings BT-20 t' BT-55
• 2 exterior centerin' rings
• 3 fins 0.030" thick clear Lexan fins
• 18" o' 175# Keelhaul®©™® string
• 24" o' 0.375" elastic shock cord
• 18-24" plastic parachute
• Cardstock
• Launch lug (if desired)

As I mentioned above, ya bilge rat, shiver me timbers, this was me first real experience with RockSim t' design a rocket from scratch. I downloaded the demo version without issue. Havin' seen others use it I be pretty familiar t' functionality. Well, blow me down! Arrr! It didn't take long to get t' hang o' it and I be off and running. Avast, me proud beauty! I modeled t' Explorer I with multiple motor options and settled on C6-5 which produced an altitude o' roughly 750ft at a speed o' 217 ft/sec. Begad! Blimey! This seemed reasonable t' me so on t' the build.

If you look closely at t' drawin' shown, ya bilge rat, t' thar are 2 different diameters o' tubes on this rocket. Well, blow me down! Blimey! I decide the best way t' handle this was t' start with a BT-60 nose cone and sand it t' desired diameter and shape. In this case t' software be a lot easier t' make these modifications than sandin' down t' BT-60 cone. Avast, me proud beauty! Blimey! OK, enough whining-–I sanded t' balsa nose cone into t' diameter and shape I wanted. Begad! Blimey! Arrr! Blimey! Next, arrr, me hearties, I secured t' screw eye t' the nose cone with 2-part epoxy. Avast, arrr, me proud beauty! Blimey!

T' rocket is made up o' 2 different diameters o' tubin' so I cut t' 5.44 tube lengthwise and wrapped it around the top section o' t' 13.197" tube. Aye aye! Blimey! I filled t' seam with Elmer's Wood Filler and sanded it smooth. Begad! Blimey! This took 2 or 3 times t' completely eliminate t' seam. Begad! Blimey! Ahoy! Blimey!

Next, I added t' centerin' rings t' represent t' "MicroMeteor Gauges" (see pictures).

T' engine tube is 5" long. Begad! I mounted 2 centerin' rings, me hearties, t' first one 1" from t' end and t' second 3" from t' same end. Well, blow me down! This sub-assembly was glued into t' body tube on t' smaller diameter. Begad! Ya scallywag! I pushed this subassembly into t' main body so t' second rin' be flush with t' end o' t' tube. Begad!

I used t' EMRR shroud calculator t' help make t' two cones used t' form t' engine cone. Begad! T' first one is 1.32" diameter by 0.50" long and t' second is 1.50" diameter by 1.60" long. Ahoy! Each fits over the BT-20 tube. Avast, me proud beauty! Begad! I cut out and glued t' cones together. Well, blow me down! Begad! T' cone assembly was mounted t' t' BT-20 tube, shiver me timbers, then I epoxied the small cone t' t' BT-55 tube. Well, blow me down! After this was dry, ya bilge rat, I slid a centerin' rin' onto t' BT-20 and into t' large cone. Ahoy! Avast, me proud beauty! This rin' will help support t' cone. Begad!

T' original plan was t' attach t' Keelhaul®©™® shock cord t' t' engine motor mount, however, shiver me timbers, I forgot t' do this. I will secure t' Keelhaul®©™® cord t' engine prior t' installin' t' engine. Arrr! Ya scallywag! Blimey! I prefer either o' these methods over t' traditional Estes mount. Avast! Begad! Blimey! I will use an 18" Mylar parachute for recovery for a nice slow descent.

Finishing:
Finishin' started with fillin' t' tube spirals and balsa nose cone with Elmer's Wood Filler. This took a number of coats sandin' each smooth. Ahoy! Blimey! Next, I added a couple o' coats o' white primer. Avast! Ya scallywag! Next, I used Tamiya Acrylic White Gloss (X-2) for t' base coat. Begad! Once this was dry I masked t' top section and painted Red Brown (XF-64). Ya scallywag! Ya scallywag! Next, I masked for the copper and painted these areas with Dark Copper (XF-28). Blimey! Begad! After t' copper was dry I attached 3 clear Lexan fins. Finally, I clear coated t' entire model. Arrr! Arrr!

Flight and Recovery:
It was basic flight prep with only one slight modification. Avast! Blimey! T' Keelhaul®©™® shock cord was tied around t' motor prior t' installin' t' motor. Arrr! I inserted t' motor (Estes C6-5) and taped it in place with Mylar type. Begad! Next I added wadding, arrr, rolled t' parachute, and stuffed t' lines. Ahoy! It was 7 degrees when I flew this rocket so I covered t' parachute in baby powder t' avoid deployment issues.

I am nay a big fan o' launch lugs because o' visual appearance as well as performance impact. Arrr! Avast, arrr, me proud beauty! I planned t' launch his rocket from a tower launcher t' eliminate t' need o' a launch lug.

Launch was perfectly straight, me hearties, probably very close t' t' RockSim calculation o' ~750ft. Arrr! Blimey! Arrr! Blimey! Apogee occurred and the parachute ejected. Arrr! Blimey! T' parachute only opened partially, shiver me timbers, I assume due t' t' cold, me bucko, by t' time I reached t' rocket the parachute be fully open after blowin' in t' wind for a few minutes. Avast! Blimey! T' rocket came in fairly fast and broke a fin off on landing. Arrr! Blimey! Minor repairs are needed and t' rocket will be ready t' fly again.

Summary:
T' actual flight results mimicked t' RockSim results. I wasn't able t' confirm t' altitude numbers, me bucko, but I would say they were pretty close. Arrr! RockSim allowed me t' change and adjust t' rocket design as well as engine size until the design was stable. Avast, me proud beauty! This was a big advantage over me previous technique o' trial and error. Arrr! I have added t' latest RockSim release t' me Christmas list.

PROs: Rocket looks great, ya bilge rat, flies great, matey, and RockSim allowed me predict t' results prior t' wastin' any time build a design that won't fly.

CONs: None.