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. Aye aye! BT-50 18" 1 ea. Ahoy! Blimey! 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, I thought it would be a good idea t' try several stagin' and clusterin' ideas that I had been thinkin' about. Begad! 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. Blimey! Arrr! Simulations indicate that air stagin' an E9 t' two C6-7's would result in an altitude o' about 1000 meters. Arrr! Avast, shiver me timbers, me proud beauty! Lots o' fun! So I purchase a couple o' G-DC kits. Begad! Ya scallywag! Before they arrived, shiver me timbers, I saw another G-DC at Orangeburg that was very similar. Avast, me proud beauty! 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, ya bilge rat, ya bilge rat, I thought t' sleeper approach was probably too common and that someone else would probably do it. Avast! I still have most o' t' g-dc parts from one kit and an unopened kit. Well, blow me down! 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. 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, me bucko, I needed a larger tube than was in t' parts list for my concept, shiver me timbers, me hearties, so I started thinkin' about stagin' a cluster t' single sustainer engine. Arrr! Well, blow me down! Then I thought about aimin' t' burn through o' t' boosters at the sustainer engine. Begad! This is how t' Vector concept originated. Ya scallywag!

Design:

A concern in Vector's conceptual design be what would happen if one o' the engines in t' booster cluster didn't ignite. Begad! Avast, me proud beauty! Blimey! So, me bucko, in order t' make Vector stable even in t' event o' ignition failure, t' thrust o' each booster was directed at t' center o' pressure. Aye aye! Blimey! If one (or two) o' t' booster engines failed t' ignite, me hearties, 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, t' rocket would remain stable and vertically orientated; however, matey, it would also "walk" horizontally. Well, blow me down! When describin' this rocket t' my engineer buddies, one o' them told me that after a nominal flight, matey, 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, arrr, they must be cut with t' proper shape. Avast, me proud beauty! 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. Aye aye! 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. Avast! Glue t' BT50-20 centerin' rin' flush on one end. Glue each o' t' three BT-20 booster tubes to the ¾" length o' BT-20. T' top o' t' booster tubes should touch the BT50-20 centerin' ring. Blimey! Ya scallywag! I used tape t' keep t' booster tubes aligned while the glue cured. Avast!

After t' glue attachin' t' tops o' t' booster tubes has cured, glue the joints where t' three booster tubes meet. 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. Arrr! Cut two ¼" holes (on opposite sides o' t' tube) centered 5/16" from t' end (I used a hole punch). Begad! This end will be t' top end o' t' booster shroud. Blimey! Test fit the booster shroud by slidin' it over t' BT50-20 centerin' ring. Well, blow me down! T' bottom o' the booster vent holes should be flush with t' centerin' ring. Avast! 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. Well, blow me down! Blimey! T' left side of the booster fins guide be t' leadin' edge. Blimey! Cut t' fins so that t' grain is parallel t' t' leadin' edge. Arrr! Blimey! i suggest that you lay out t' sustainer fins first though. Glue t' booster fins t' t' booster tubes so that t' trailing tip is flush with t' bottom o' t' booster tube. Ahoy! Use some thinned fill-n-finish t' smooth out t' joints, 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, ya bilge rat, but I fly on a huge sod farm. If your field is limited, ya bilge rat, ya bilge rat, you may want t' modify t' design t' use an 18 mm motor mount.

T' main body tube is 13 3/8" long. 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, me bucko, me hearties, Vector Sims t' 2300' with (3) b6-0 booster and a D12-7 sustainer motors! 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, friction fit t' D12-7 sustainer motor into the sustainer leavin' about ½" exposed. Arrr! Wrap ¼" tape several times around t' bottom o' t' B6-0 booster motors and then friction fit t' motors into t' booster tubes. Begad! Aye aye! Test fit t' booster on t' sustainer. T' booster should nay fall off under when holdin' t' sustainer; however, it should nay take too much additional pull t' remove. Arrr! Add tape t' t' D12-7 to adjust t' fit.

Left: Vector on t' pad. Avast! Note clusterin' whips.

T' first launch o' Vector was at t' February 9^th ICBM launch at Orangeburg, SC. Arrr! Ya scallywag! Blimey! It was windy, and I waited all day, but t' wind never died down. Aye aye! Ya scallywag! Blimey! For t' first flight, 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, shiver me timbers, I thought all three booster engines lit (later I found only 2 did) t' boost be straight with some weathercocking. Well, arrr, blow me down! Booster separation was good, t' D12 lit, shiver me timbers, 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.

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

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

Lessons Learned:

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

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