T' Mercury Transport is a new design from Essence Aerospace Technologies (EAT). Its main purpose is t' transport 4 passengers t' 91.8 Million Kilometers t' t' planet Mercury for observation, study and experimentation in a high temperature, zero gravity, me hearties, high sun-radiation environment. T' Mercury Transport has fins that are suspended over t' inner Fusion Proton Rod Reactor Core. Arrr! Blimey! T' fins are in a test configuration for future interstellar travel and t' assist in coolin' t' core as t' ship passes close t' stars (such as our Sun). Begad! Ya scallywag! Blimey! T' ship is primarily designed for long distance travel. Begad! Blimey! In fact, 95% o' t' entire ship is a reactor to allow t' ship t' travel t' distance needed.

I began preparin' t' build a Mid-High Power rocket with this unique (at least I've never seen anythin' like it) fin and body configuration. Ya scallywag! Well, blow me down! So, me bucko, in preparation I wanted t' build a smaller 18mm prototype to test design and stability. Arrr! This article describes t' assembly and performance of t' prototype which turned out t' be a nice rocket in itself. Ahoy! Avast! There is also a thread on T' Rocketry Forum that I initiated when I started this process. Avast, matey, me proud beauty!

I decided t' start with an Estes Big Bertha kit t' get the larger diameter tube, motor mount, parachute and especially t' nose cone. So with that bein' said, here's me parts list:

• (1) 2" length BT60 (1.637" diameter) Tube - From Big Bertha Kit
• (1) 3" length BT60 (1.637" diameter) Tube - From Big Bertha Kit
• (1) PNC-60MS Nose Cone - From Big Bertha Kit
• (1) 18mm Motor Tube - From Big Bertha Kit
• (1) 18mm Thrust Rin' - From Big Bertha Kit
• (1) 18mm Motor Hook - From Big Bertha Kit
• (2) 18mm t' BT60 Centerin' Rings - From Big Bertha Kit
• (1) 18mm t' 24mm Centerin' Rin' - Use a cut from a spent 24mm motor if needed
• (3) 24mm t' BT60 Centerin' Rings - Cut from 1/16" balsa or shoebox
• (2) 24mm t' BT60 Transition - Cut from t' Big Bertha Kit's Picture Card
• (1) 3/32" Thick, me hearties, 3" x 36" Balsa
• (1) 15" length o' 24mm Apogee Tube
• (1) 32" o' Keelhaul®©™® Shock Tether
• (1) 24" Elastic Shock Cord - From Big Bertha Kit
• (1) 1/8" Launch Lug / Cut in Half - From Big Bertha Kit
• (1) 18" Parachute with Center "Estes" Circle cut out - From Big Bertha Kit

CG=11 1/2" from top (see RockSim File)

ASSEMBLY:

1. Cut a 2" and a 3" section off o' t' BT60 tube. Arrr! I use a piece o' paper t' wrap around t' tube t' ensure it is even then draw a line all t' way around. Alternatively, I use maskin' tape t' make an even circle around t' tube. Ya scallywag! Use a sharp hobby knife t' make t' cuts. Usually two or three passes. Begad! Don't try t' do it on t' first shot and take your time. Cut 2" off one side o' t' BT60 and 3" off t' other so that you have perfect, arrr, arrr, shiver me timbers, factory cut edges on each side.
2. Cut t' Apogee 24mm tube t' a length of 14.5".
3. Cut out (3) Centerin' Rings from 1/16" balsa. Begad! Ya scallywag! Blimey! I used t' centerin' rings provided with t' Big Bertha kit t' cut t' outer edge and then traced t' 24mm tube for t' inner circle. I then used sandpaper to shape them t' fit. Aye aye! Test fit them over t' 24mm tube and into t' BT60 tubing.
4. Assemble t' motor mount per t' Big Bertha Instructions with (1) major exception. Ya scallywag! Leave t' upper centerin' rin' 3/4" from t' top of t' tube.
5. Tie t' Keelhaul®©™® Shock Tether around t' motor tube top (that 3/4" space) and then slide the 18mm - 24mm centerin' rin' over t' Shock Tether and glue even t' t' top of t' Motor Tube. Avast, me proud beauty! Blimey! Wait until dry. Begad! Blimey! Begad! Blimey! Thread t' Shock Tether through t' Motor Tube t' get it out o' t' way.
6. Glue t' motor mount into t' 3" section o' BT60 tubin' so that t' lower centerin' rin' is flush with t' bottom and your cut edge is up. Begad! Avast! Let dry.
7. Slide one o' centerin' rings you made over t' 24mm tube and test fit it into t' lower (3") section. T' tube should slide over the 18-24mm centerin' rin' on t' motor tube and down until it rests on the motor mounts upper centerin' ring. Avast, me proud beauty! T' push t' balsa centerin' rin' down until it fits just inside o' t' 3" section. Avast, shiver me timbers, me proud beauty! Mark t' 24mm tube for the alignment o' this centerin' ring. Pull it all out and slide t' centerin' ring to 1" or so higher than t' mark you just made. Arrr! Blimey! Apply glue t' t' inside of t' 24mm tube and around t' mark on t' 24mm tube. Avast! Slide it back into the 3" section onto t' inside centerin' rin' until it touches t' motor tube centerin' ring. Slide down t' balsa centerin' rin' until it is just inside and flush with t' 3" section. Avast! Let dry.
8. Place a mark at 1/2" on t' top o' t' 24mm tube. Slide another balsa centerin' rin' onto t' 24mm tube about 1" o' so beyond t' 1/2" mark. Arrr! Apply a rin' o' glue at t' 1/2" mark and at the very end o' t' tube. Slide t' balsa centerin' rin' up t' t' 1/2" mark. Begad! Place t' 3rd balsa centerin' rin' onto t' top o' t' 24mm tube so that it is flush. Make sure both centerin' rings are equally spaced all t' way around. Avast, me proud beauty! Ya scallywag! Let dry.
9. Put a rin' o' glue on t' inside o' t' 2" section of BT60 tubin' on t' cut edge side. Avast! Slide t' 24mm tube into t' BT60 tube until t' lower centerin' rin' is flush with t' bottom. Ahoy! Lay this assembly on a table and roll it gently t' ensure t' bottom 3" tube and top 2" tube are in alignment. Well, me bucko, blow me down! Use a straight-edge t' check.
10. (10) Cut t' transitions usin' t' calculations in Tim Van Milligan's Model Rocket Design and Construction Book. Begad! Blimey! Avast, me proud beauty! Blimey! I used t' formulas, but cut full circles and then sized t' transition from t' over-lap. Begad! Blimey! Tim's book does show you how t' calculate t' angle/degrees that could be measured, arrr, me hearties, but I found my method t' work fine.
11. Glue transitions in place. Ya scallywag! Avast! If they are slightly bigger than t' BT60 tube, me hearties, that's okay. Avast, me proud beauty! It can be trimmed with a sharp hobby knife after t' glue has dried.
12. Cut t' (6) Coolin' Fins from t' 3/32" Balsa. Arrr! Avast, me proud beauty! They are 11mm wide and 14 5/8" long. T' angle is cut on both ends by measuring 1/2" on t' top side and cuttin' from that point t' t' lower corner. Unfortunately t' grain runnin' parallel with t' length o' t' Coolin' fins is the easiest cut and realistically t' only way o' havin' this 1 piece. The makes t' attachment a little vulnerable t' breakin' along t' grain.
13. Cut t' (6) Main Fins from t' 3/32" Balsa using the pattern from RockSim and alignin' t' t' 1/2" angle cut on t' lower section o' t' Coolin' Fins. Well, blow me down! Position these so that balsa grain is parallel to the leadin' edge.
14. Mark your tube for (3) fins usin' t' Estes Fin marking guide. Turn t' tube so that (3) additional marks can be made exactly half-way between t' first (3). This way you have (6) fin marks. Line t' body up t' a door jam and extend t' lines across both sections o' BT60 tubes. Avast, me proud beauty! T' inner 24mm tube does nay need marked.
15. STOP! Weird as it sounds, arrr, now be t' time to finish, matey, matey, smooth and paint t' inner tube section. I masked t' upper and lower BT60 tubes at t' transition and painted it Florescent Orange (Krylon). Arrr! I didn't worry about gettin' paint on t' transitions.
16. Now assemble t' fins t' t' rocket. I applied (1) Coolin' Fin and (1) Main Fin at a time. Once all t' fins are attached use you favorite fillet glue and method. I used wood glue for t' entire assembly process.
17. Push t' Keelhaul®©™® Tether through t' motor tube and up through t' 24mm tube. Well, blow me down! Attach t' Big Bertha's elastic t' t' Keelhaul®©™® and tie t' elastic t' t' Nose Cone.
18. Cut t' center section our o' t' provided Parachute. Attach t' Parachute t' t' Nose Cone. You will need t' fold t' parachute in such a way that it will fit into t' 24mm tube as thar be nay enough room for it t' fit in t' upper BT60 section.
19. Cut t' Big Bertha provided launch lug in half and place 1 against a Coolin' Fin on t' top section and t' other against t' same Coolin' Fin on t' lower section.
20. CAREFUL! You may have noticed that t' Cooling Fins are "flexy" both back and forth and up and down. Arrr! Begad! Don't squeeze them. Blimey! Blimey! Try t' handle t' rocket from t' top or bottom.
21. Now carefully work maskin' paper (I use computer paper) in betwixt t' Coolin' Fin gaps and pull it very tight t' protect t' Orange finish o' t' 24mm tube. Avast, me proud beauty! Begad! Expose t' transitions. Avast, me proud beauty! Use tape as needed t' keep it held tightly in place.
22. (22) Finish and paint t' rocket. Begad! Dark Navy Blue (Krylon) is what I used. Begad! Begad! I regret nay spendin' more time on me finish, shiver me timbers, but it was supposed t' simply be a prototype.

Before I get into t' flyin' o' t' Mercury Transport, matey, I want t' discuss a new findin' for me about RockSim Free Form Fin Design. What I found is that when you go into t' Free Form Edit page t' point at "0, 0" and t' farthest point t' t' right at "x, arrr, 0" are set. Avast, me proud beauty! Blimey! In other words t' "0" on these two points be t' established base line and are nay changeable in RockSim. Arrr! If you go ahead and draw out your fin pattern with t' right-most point remainin' as t' "x, 0" then the fin will "touch" t' body tube for t' entire length o' t' root edge. In t' Mercury Transports case, t' fin spanned across t' two different diameters o' t' tubes and therefore this made t' root edge conform t' the inner tube as well as t' outer tube. Blimey!

Please excuse me use o' bright green on t' fins here, it is simply t' show t' difference.

My design be for it t' "bridge" t' inner tube, nay touch it. Avast, arrr, me proud beauty! T' make this work, me bucko, I had t' move t' right-most point t' be the second point from t' left (in me case "0.5, me bucko, arrr, 0"). Arrr! Avast, me proud beauty! T' third point from t' left had t' be right above this point (in me case "0.5, 0.001"). Arrr! By settin' this t' be "0.001" on t' y-axis I was able to create t' "bridge". Begad! After spannin' t' inner tube length includin' transitions I had two points again. One was at "14, 0.001" and t' other right below it was "14, shiver me timbers, 0" which brought t' fins root back into contact with t' lower tube section.

What difference does it make? Major! T' position o' the CP with t' root touchin' made t' rocket appear, by calculation, me hearties, t' be unstable or marginally stable. Aye aye! With t' fin true t' design t' rocket, by calculation, was over stable. Ahoy! RockSim calculations still had t' CP on the rocket, while Barrowman had t' CP way off t' back o' t' rocket. Well, blow me down! Flight proved t' stability o' t' design!

FLIGHT/RECOVERY:

My first flight be on an Estes B6-4. It was absolutely perfect and I can't describe it any differently. Aye aye! Stable and straight. Blimey! It is a little heavier model so t' lift-off is nay lightnin' fast allowin' you t' enjoy it. At apogee t' rocket seemed t' hang parallel with t' ground and just as it appeared t' stop and start down ejection occurred. Arrr! T' 'chute opened and it descended safely t' recovery.

T' second flight be on an Estes C6-4. Begad! Again stable and straight, just higher. Blimey! Begad! At apogee it again was parallel t' t' ground when ejection occurred. One panel on t' plastic 'chute stuck t' itself causin' less than full 'chute opening. Begad! That be okay because it be a little windy and this thin' drifted down t' length o' t' field. Ahoy! While reloadin' t' 'chute I squeezed t' Coolin' Fins a bit too hard and cracked one at t' attachment to the upper tube. Ahoy! Nay broken through. Ahoy!

T' third flight was back on t' Estes B6-4 for another repeat o' t' first flight. This time me 'chute got tangled in me heat shield and did nay open. Recovered with no damage.

I place t' rocket in me box, satisfied with three great flights and I had three perfect lift-off pictures. Begad! As I headed back t' t' car I heard a crack o' one o' t' Main Fins as I had squeezed t' box a bit too hard. T' fin be nay broken completely off though.

I repaired t' two cracks usin' CA. I lost, me hearties, or rather me computer ate, me three launch pictures so I was disappointed. Well, blow me down! Aye aye! Blimey!

T' next day me son and I ran out t' do a single flight for t' sole purpose o' gettin' a flight picture. Got it on a B6-4 for a repeat of t' first flight's performance.

SUMMARY:

T' Mercury Transport has inspired me t' press on with my 4" / 2.6" / 4" version. Ya scallywag! Arrr! Can you scale up a rocket without impactin' CP/CG relationship? Read Apogee's Newsletter Issue 80.

I would suggest that you strengthen t' fins by CA'ing or a light paper cover. Aye aye! Whatever your favorite method is. Ya scallywag! Other than that, I think it is a nice rocket and would love t' hear and see any experiences that you have buildin' and flyin' this design!