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. Arrr! BT-50 18" 1 ea. Arrr! Blimey! BT-20 18" 1 ea. 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, me hearties, matey, I thought it would be a good idea t' try several stagin' and clusterin' ideas that I had been thinkin' about. Begad! My first idea was 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! Avast, me proud beauty! Simulations indicate that air stagin' an E9 t' two C6-7's would result in an altitude o' about 1000 meters. Avast, me proud beauty! Ahoy! Lots o' fun! So I purchase a couple o' G-DC kits. Before they arrived, I saw another G-DC at Orangeburg that be very similar. Arrr! Ahoy! In this case, shiver me timbers, t' basher used t' standard 18 mm center mount and two 13 mm outboards. Begad! On t' way home, reconsiderin' my approach, I thought t' sleeper approach was probably too common and that someone else would probably do it. I still have most o' t' g-dc parts from one kit and an unopened kit. Avast, me proud beauty! 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. Blimey! Begad! 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, matey, I needed a larger tube than was in t' parts list for my concept, ya bilge rat, so I started thinkin' about stagin' a cluster t' single sustainer engine. Avast, me proud beauty! Then I thought about aimin' t' burn through o' t' boosters at the sustainer engine. Avast! Ahoy! 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. Begad! So, me hearties, in order t' make Vector stable even in t' event o' ignition failure, me hearties, me hearties, t' thrust o' each booster was directed at t' center o' pressure. Avast, me proud beauty! If one (or two) o' t' booster engines failed t' ignite, ya bilge rat, shiver me timbers, 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). Avast! In theory if this occurred, me bucko, t' rocket would remain stable and vertically orientated; however, ya bilge rat, it would also "walk" horizontally. When describin' this rocket t' my engineer buddies, me hearties, me bucko, one o' them told me that after a nominal flight, I would have to intentionally launch t' rocket on only two booster engines. Aye aye! This inadvertently happened on t' first flight (see flight reports.)

Booster Construction:

In order t' Siamese t' three BT-20 booster tubes together, they must be cut with t' proper shape. 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. Avast! Avast, arrr, me proud beauty! 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. Avast, me proud beauty! Well, me bucko, blow me down! 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. Begad! Aye aye! I used tape t' keep t' booster tubes aligned while the glue cured. Begad!

After t' glue attachin' t' tops o' t' booster tubes has cured, me hearties, glue the joints where t' three booster tubes meet. After this glue has cured, me bucko, 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. Cut two ¼" holes (on opposite sides o' t' tube) centered 5/16" from t' end (I used a hole punch). This end will be t' top end o' t' booster shroud. Begad! Blimey! Test fit the booster shroud by slidin' it over t' BT50-20 centerin' ring. Begad! Blimey! T' bottom o' the booster vent holes should be flush with t' centerin' ring. 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. Begad! 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. Avast, me proud beauty! Blimey! i suggest that you lay out t' sustainer fins first though. Blimey! Aye aye! Glue t' booster fins t' t' booster tubes so that t' trailing tip is flush with t' bottom o' t' booster tube. Avast, me proud beauty! 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, but I fly on a huge sod farm. 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. Begad! Ahoy! I added 2 oz o' weight t' t' nose cone t' further increase stability and t' reduce t' altitude. Well, blow me down! Even with the additional 2 oz, matey, 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, ya bilge rat, friction fit t' D12-7 sustainer motor into the sustainer leavin' about ½" exposed. Blimey! Well, blow me down! Wrap ¼" tape several times around t' bottom o' t' B6-0 booster motors and then friction fit t' motors into t' booster tubes. Test fit t' booster on t' sustainer. T' booster should nay fall off under when holdin' t' sustainer; however, me hearties, shiver me timbers, it should nay take too much additional pull t' remove. Arrr! Arrr! Add tape t' t' D12-7 to adjust t' fit.

Left: Vector on t' pad. Arrr! Note clusterin' whips. Well, blow me down!

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

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

A premature ejection caused t' parachute t' strip, me bucko, but t' sustainer tumbled down safely with t' nose cone attached.

When I approached t' booster I noticed two blue objects on the ground. Begad! Blimey! I thought t' myself, matey, "not good" upon closer inspection, apparently only two booster motors lit on t' pad. Arrr! Blimey! When t' sustainer lit, arrr, the thrust lit t' third booster motor from t' top, me bucko, 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 be consumed. Ahoy! Blimey! It never occurred t' me that could have happened I needed a new booster, me hearties, but at least I knew t' Vectored thrust worked and t' rocket was stable on only two booster motors.

When I rebuilt t' booster, I decided t' build two, just in case. Well, blow me down! Blimey! I flew Vector t' second time on May 11, arrr, again at O'burg. Again, matey, it be windy and I waited most o' t' day, matey, but t' wind never let up, so I swapped t' 'chute for a streamer. Aye aye! Again, I used (3) B6-0's for t' booster and a D12-7 for the sustainer. This time t' RSO let me launch from t' model rocket pads. Aye aye! Arrr! At this close range, t' Vectored thrust be very noticeable. Blimey! It be obvious all three boosters were lit and Vector was screamin' straight up. Begad! At about 200' the sustainer lit and Vector momentarily went out o' sight. Aye aye! Well, blow me down! 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. Avast! T' Vectored thrust is pretty cool t' see. Avast! Aye aye! T' insure successful cluster ignition, me hearties, it may be a good idea t' use better igniters. Avast, me proud beauty! For t' second flight, arrr, 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, arrr, 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