VECTOR
by Scott Hamlin

Features: High Altitude Two Stage Model Rocket 3 Engine Clustered Booster Vectored Booster Thrust 3 Engine Booster t' Single Engine Sustainer Staging 18 mm Boosters 24 mm Sustainer Parts list: 1 ea. BT-50 18" 1 ea. Aye aye! BT-20 18" 1 ea. Ya scallywag! BT-50 nosecone 1 ea. BT50-20 centerin' rin' 3" x 12" balsa at 3/32" launch lug and recovery system as necessary for safe operation

Intro:

When I read about t' kit-bask theme o' DESCON-X, arrr, I thought it would be a good idea t' try several stagin' and clusterin' ideas that I had been thinkin' about. Ya scallywag! My first idea be t' build a "sleeper" Gemini DC by makin' t' rocket appear stock while usin' a 24 mm center engine mount with two outboard 18 mm mounts. Well, blow me down! Simulations indicate that air stagin' an E9 t' two C6-7's would result in an altitude o' about 1000 meters. Ya scallywag! Avast, me proud beauty! Lots o' fun! So I purchase a couple o' G-DC kits. Before they arrived, arrr, I saw another G-DC at Orangeburg that was very similar. In this case, t' basher used t' standard 18 mm center mount and two 13 mm outboards. Aye aye! On t' way home, reconsiderin' my approach, arrr, I thought t' sleeper approach be probably too common and that someone else would probably do it. Ahoy! I still have most o' t' g-dc parts from one kit and an unopened kit. Ya scallywag! I'm thinkin' about puttin' t' two together t' make a Modroc with four outboardsa

Another idea I've been considerin' is stagin' a D t' two or three B's or C's. Begad! Blimey! My theory is that if thar be a moderate separation betwixt t' stages, the burn through from t' D will ignite all o' t' sustainer engines. Unfortunately, I needed a larger tube than was in t' parts list for my concept, me bucko, so I started thinkin' about stagin' a cluster t' single sustainer engine. Aye aye! Blimey! Then I thought about aimin' t' burn through o' t' boosters at the sustainer engine. This is how t' Vector concept originated.

Design:

A concern in Vector's conceptual design was what would happen if one o' the engines in t' booster cluster didn't ignite. Aye aye! Avast! So, matey, in order t' make Vector stable even in t' event o' ignition failure, me hearties, t' thrust o' each booster was directed at t' center o' pressure. If one (or two) o' t' booster engines failed t' ignite, me bucko, me bucko, t' Vector addition o' t' remainin' engines would have an axial component (makin' t' rocket go up) and a tangential component through the C_P (makin' t' rocket go horizontal). In theory if this occurred, me hearties, t' rocket would remain stable and vertically orientated; however, shiver me timbers, it would also "walk" horizontally. Ahoy! Well, blow me down! When describin' this rocket t' my engineer buddies, matey, one o' them told me that after a nominal flight, ya bilge rat, I would have to intentionally launch t' rocket on only two booster engines. Begad! This inadvertently happened on t' first flight (see flight reports.)

Booster Construction:

In order t' Siamese t' three BT-20 booster tubes together, shiver me timbers, they must be cut with t' proper shape. Blimey! Blimey! Blimey! Blimey! I solved t' intersection o' t' three tubes numerically and plotted them with me printer t' be used as a guide (see below). T' scales are in inches. Ahoy! Blimey! Avast, arrr, me proud beauty! Blimey! Blimey! Blimey! Each booster tube is 6" long, but if you overlap the cutout area you can get 4 from an 18" tube.

Cut a ¾" length o' BT-20 from t' scrap pieces. Glue t' BT50-20 centerin' rin' flush on one end. Begad! Glue each o' t' three BT-20 booster tubes to the ¾" length o' BT-20. Begad! T' top o' t' booster tubes should touch the BT50-20 centerin' ring. Ahoy! Well, blow me down! I used tape t' keep t' booster tubes aligned while the glue cured. Aye aye! Arrr!

After t' glue attachin' t' tops o' t' booster tubes has cured, glue the joints where t' three booster tubes meet. Well, blow me down! Blimey! Blimey! Blimey! After this glue has cured, use a ¼" wide strip o' tissue paper t' reinforce t' joints and t' plug any small holes.

Cut a 2" length o' BT-50 for t' booster shroud. Blimey! Blimey! Cut two ¼" holes (on opposite sides o' t' tube) centered 5/16" from t' end (I used a hole punch). Ya scallywag! Blimey! Ahoy! Blimey! This end will be t' top end o' t' booster shroud. Ahoy! Blimey! Test fit the booster shroud by slidin' it over t' BT50-20 centerin' ring. T' bottom o' the booster vent holes should be flush with t' centerin' ring. Blimey! Blimey! Ahoy! Blimey! Glue t' booster shroud on by applyin' glue t' t' centerin' rin' and t' area o' t' booster tubes when t' shroud touches.

Left: booster fin plotted on ¼" grid. Avast! Avast! T' left side of the booster fins guide be t' leadin' edge. Arrr! Cut t' fins so that t' grain is parallel t' t' leadin' edge. Aye aye! i suggest that you lay out t' sustainer fins first though. Begad! Glue t' booster fins t' t' booster tubes so that t' trailing tip is flush with t' bottom o' t' booster tube. Arrr! Use some thinned fill-n-finish t' smooth out t' joints, me bucko, shiver me timbers, ya bilge rat, paint, and t' booster is ready for flight.

Sustainer Construction:

T' sustainer is a straightforward 3fnc (three fins and a nose cone) design. I used a D12-7 for t' sustainer motor, me bucko, but I fly on a huge sod farm. Avast! If your field is limited, you may want t' modify t' design t' use an 18 mm motor mount.

T' main body tube is 13 3/8" long. Ya scallywag! Blimey! Aye aye! Blimey! I added 2 oz o' weight t' t' nose cone t' further increase stability and t' reduce t' altitude. Even with the additional 2 oz, Vector Sims t' 2300' with (3) b6-0 booster and a D12-7 sustainer motors! Blimey! Place t' launch lug at t' center o' mass with engines loaded.

Sustainer Booster

Vector loaded for bear

Vector Flight Data:

To prep Vector for launch, matey, friction fit t' D12-7 sustainer motor into the sustainer leavin' about ½" exposed. Begad! Wrap ¼" tape several times around t' bottom o' t' B6-0 booster motors and then friction fit t' motors into t' booster tubes. Aye aye! Blimey! Test fit t' booster on t' sustainer. T' booster should nay fall off under when holdin' t' sustainer; however, shiver me timbers, me bucko, it should nay take too much additional pull t' remove. Begad! Aye aye! Blimey! Add tape t' t' D12-7 to adjust t' fit.

Left: Vector on t' pad. Aye aye! Note clusterin' whips. Avast, me proud beauty!

T' first launch o' Vector was at t' February 9^th ICBM launch at Orangeburg, SC. Blimey! It was windy, and I waited all day, matey, arrr, but t' wind never died down. Arrr! For t' first flight, shiver me timbers, t' RSO asked me t' load Vector on a high power pad in order t' provide more distance betwixt it and t' spectators.

At ignition, arrr, arrr, I thought all three booster engines lit (later I found only 2 did) t' boost was straight with some weathercocking. Begad! Blimey! Booster separation was good, me bucko, t' D12 lit, and Vector was almost out o' sight.

A premature ejection caused t' parachute t' strip, but t' sustainer tumbled down safely with t' nose cone attached. Ahoy! Arrr!

When I approached t' booster I noticed two blue objects on the ground. I thought t' myself, "not good" upon closer inspection, apparently only two booster motors lit on t' pad. Blimey! Arrr! When t' sustainer lit, the thrust lit t' third booster motor from t' top, burnin' t' booster into two pieces. In t' above photo, it is obvious that t' booster motor on t' left never developed thrust out o' its nozzle, yet t' propellant was consumed. It never occurred t' me that could have happened I needed a new booster, ya bilge rat, but at least I knew t' Vectored thrust worked and t' rocket was stable on only two booster motors. Blimey!

When I rebuilt t' booster, I decided t' build two, arrr, just in case. Blimey! Aye aye! I flew Vector t' second time on May 11, matey, ya bilge rat, again at O'burg. Begad! Blimey! Again, shiver me timbers, it be windy and I waited most o' t' day, but t' wind never let up, so I swapped t' 'chute for a streamer. Again, I used (3) B6-0's for t' booster and a D12-7 for the sustainer. Arrr! Begad! This time t' RSO let me launch from t' model rocket pads. Begad! At this close range, shiver me timbers, t' Vectored thrust was very noticeable. Aye aye! It be obvious all three boosters were lit and Vector was screamin' straight up. Aye aye! At about 200' the sustainer lit and Vector momentarily went out o' sight. Ya scallywag! When I re-established tracking, me hearties, Vector was on t' streamer and recovery be nominal.

Lessons Learned:

T' canted, matey, Vectored motor design is unique and generated a lot o' interest at t' launch. Begad! Avast, me proud beauty! T' Vectored thrust is pretty cool t' see. Begad! T' insure successful cluster ignition, it may be a good idea t' use better igniters. Avast! For t' second flight, matey, me hearties, I soldered leads onto t' solar igniters as I think t' wire whips failed on t' first flight. It may also be a good idea t' paint t' inside of the booster with high heat paint.

Finally, me hearties, arrr, as I mentioned earlier it may be a good idea t' use an 18 mm motor for t' sustainer on t' other hand, me hearties, me bucko, for t' next launch, arrr, shiver me timbers, I plan t' use (3) C6-0's for t' booster and a E9-8 for t' sustainera