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G Superroc R&D

"Development Of A High-Scoring G Superroc By Use Of Optimized Engine Choice, Conventional Design, And Conventional Construction Methods."

2007 R&D at NARAM-49
Second Place

Southern Neutron Team
George Gassaway, Ed LaCroix, Terrill Willard, & Ryan Woebkenberg


This project was created as a necessity due to the choice of G Superroc at NARAM-49. We had theorized that the best way to go would not be with some exotic fabrication methods. Especially since the rules or interpretations of what was and was not allowed were not specific enough to trust from one month to the next, to the day the event was actually flown. Instead, we figured that the best way would be to go with conventional construction methods, with a very careful choice of engine thrust profiles. The first idea was to use two F10's (one on F10 and two E6's). But at the time F10's were not Contest certified. The next best option was to use something like a G12 reload (93 n-sec) and two E7 reloads (30 N-sec). But since the G12 reload did not have a delay and ejection charge, a model would have to be a bit more complicated, with some type of electronic ejection. That was somewhat more complex to get into at the time, as our team had a Launch Crue Regional coming up in November, so simpler approaches were attempted first, to get some real flying experience to compare with what we expected.

First Test - Oct 21, 2006      Near Childersburg, Alabama

Model used nearly all BT-80, plus a BT-60 upper section. Power was on a single G40 engine. This was the first time that we know a maximum length G Superroc model was flown.

Tony Williams with model
George with model
Starting to veer left

The model boosted faster than expected, and the body started to bend lightly to one side. It continued to bend and veer more and more to one side, finally ripping apart. We knew that a G40 would not be ideal for the event but were surprised that a mostly BT-80 model was not strong enough.

Second and Third Model Tests - November, 2006     Launch Crue Regional Holland, Indiana

Ryan Woebkenberg flew a short BT-60 model that was highly reinforced, on a G40. The reinforcement was by use of full length tube couplers, a design by Jim Stum that had been proven to work.

Ryan with reinforced BT-60 on G40
Ryan with BT-70 model (Three E9's)

Flight one flew fine, but did not close the track. The reflight also held up, but the shock cord failed, causing it to crash and be DQ'ed. Ryan flew a Back-up George sent, all BT-80, using three E9's. It worked successfully, and won the Team Division.

By Fall, we had heard that the Apogee F10's and E6 expendables had been submitted to get their Contest Certification restored. Expecting that they would be, we decided to drop the idea of a G12 and tow E7 model in favor of Two F10's or one F10 and two E6's.

Fourth Model - March 2007    Phoenix, Arizona

Ed LaCroix and George Gassaway built a prototype for the engine and airframe type we thought would be best (George was visiting for a week, including doing one of the SSS Regional meets). Maximum length (450 cm, about 14.75 feet) of BT-60, powered by one F10 and two E6's.

34" BT-60 sections
with tube joiners
F10 and two E6's prepped
Ready for launch
Ed with model

The model was test flown privately, not at a launch so as not to give away the secrets of the design approach, especially the engine power. It flew great. Boosted vertically, with very little weathercocking at all, very notable for an 8 second burn. Here is a Video of the G Superroc Test Flight. Take note that the delay on the F10 (an OLD F10) was very long, the model went into a "backslider" type of glide for a few seconds before ejection.

That test confirmed what we had theorized back in August 2006 when the event was announced for NARAM-46. By using one F10 and two E6's, it was like having one "G20" engine with an 8 second burn, at the maximum allowed 160 Newton-Seconds.

Fifth Model - April 2007, Birmingham Alabama

George made use of an old "F Superroc Duration" model built in 1980 (yellow with black fins) to try out an all black powder Maximum length G Superroc, Two E9's and two D12's. Extra BT-80 sections were added to help make it to be near maximum length. It flew very nicely. This was not a design approach considered to be capable of winning, it was done partly from curiosity and partly because the clustered main body already existed.

George before launch

Sixth and Seventh Models - July 2007    Pheonix, Arizona

Ed Lacriox built two more models.One was a BT-55 odle powered by an F10 and two E6's. This was intnded to be a "windy weather" model that we might fly shorter than maximum length. Ed and Terrill test flew it. At about 5 seconds into the boost, it suddenly bent and shredded.

BT-55 model During Assembly
BT-55 model after shred

Ed also built another all-BT-60 model, refined by having two F10 engines merged more cleanly into the BT-60 airframe thna the Fourth model which had two E6's and one F10. Tiem ran out ot test fly it.

Two F10 model during assembly
Two F10 model completed

NARAM-49 - July 2007    Kalamazoo, Michigan                          

We prepped and flew the Two F10 modle Ed built in July. We used the BRB HPR Pad, which eaisly tilts over for loading. Ed and Terrill brought a two-piece rail, 6 feet each, which with a joiner made for a 12 foot rail.

Ed & Terrill
George & Ed
Terrill, Ed, & George Loading model
Ed hooking up the Two F10 Cluster
Photo sequence: liftoff, climb, and bending just before shred.
Unfortunately, about halfway up, it started to bend left, and shredded. Also, one of the two F10's had a cato. We did not know whether the cato caused the shred or if the shred was before the cato. We were given a reflight. So, we went back to the prototype built in March, using two E6's and one F10 (modle #4). However, we were shaken by the shred of the two F10 model, as structurally both were the same. So, we removed the original tube joiners and replaced them with longer tube joiners to make the model stiffer, and also a bit heaver which reduced the velocity at cost of altitude. We had other backup models, but this was the only model left that could use the "160 N-sec G20" engine combination (in this case, one F10 and two E6's).

2nd Flight
3rd (winning) Flight
Terrill and Ed after
the last flight.
Terrill, George, & Ed
The whole winning model
The reflight using the March model flew great. But, despite four trackers, only one saw it, so the flight was a lost track. So officially under the rules, we still got to do flight one over. But time was getting tight, we might not have had time to fly two more times, so the third flight of the day was critical. Fortunately, it was tracked, and went on to easily win Team Division.

So, the engine power we theorized a year before proved out and won. So, all the time and effort we put into it was worth it. Plus, the R&D that had been done involving preparing for the event as useful in becoming a NARAM R&D project as well. Below is a summary from the report, a link for downloading the whole report as a PDF file.

The win in G Superroc, plus second in R&D, helped us win the NARAM Champion Team Trophy, and helped assure that nobody passed us so that we also won the Team National Championship for the 2006-2007 season.

Report Summary:

Our objective was to develop a highly competitive G Superroc model, without using composite fabrication, special construction, or special design tricks.

We realized that winning Superroc models are almost always maximum length, so a highly competitive G class model probably needed to be maximum length, at 450 CM (or 14.76 feet) tall.

We first built and flew a maximum length G Superroc, and quickly found out some of the problems associated with building and fly a nearly 15 foot tall rocket powered by a G engine. When that model failed, we had to work up two less-than ideal models to compete with at a Novembers regionalcontest, and get some more practical in-the-field experience at an actual contest.

Having obtained more experience, we set about to build a highly competitive model, of maximum length, which would require less structural strength than the other models that were being flown. We realized that the optimum engine choice seemed to be a cluster of long burn low thrust engines, either two F10's or one F10 and two E6's. Those choices also are rated at 160 N-sec, giving full total impulse for flying the event. For practical purposes, like using a 160 N-sec "G20" engine.

By using one of those two choices, the model would fly slower and have less structural flight loads than with any other viable G engine choice. That is the key to obtaining good flight performance out of paper/cardboard G Superrocs, reducing the flight loads so they do not have to be as strong as with other engines in the 80.01 to 160 N-sec class.

An all-BT-60 model of 450 CM was built and tested, successfully flying on an F10 and two E6's.

Refinements were made to that design, to reduce drag of the lower section with the engines and fins.

In addition to flight testing, some Rocksim simulations were run, based on some of the test models, to evaluate and compare other engine choices which had been considered. Those simulations show that higher thrust engines produce lower altitudes and often significantly higher flight loads than two F10's or one F10 and two E6's. Those simulations helped to confirm our conclusions.

We feel that we have a competitive design approach to use at NARAM-49.


Click here for a PDF Copy of the full G Superroc Report. (9.7 MB)

Click here for a NARAM-49 photo page.


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