Thrustline Aerospace Flux Probe is a "longneck"
straightforward rocket that looks like an arrow. In fact, a 13 year-old that
saw me fly it, said exactly that. Probably with some detail work, it would look
exactly like an arrow.
What makes the Flux Probe "longneck"?
It has a 0.734" diameter and is 36.75" long, giving it a 50:1 length
to diameter ratio.
I purchased it because I liked the looks of
the fins and perhaps because it did look like an arrow. It is my second
Thrustline kit, after the
The kit includes two 17" body tubes and
a 2.75" balsa nose cone to make up the 36.75" total length. There is
a 2" coupler to join the two body tubes, two thrust rings, a Kevlar
tether (36"), an elastic shockcord (36"), a 12" mylar parachute
AND a 2"x61" mylar streamer, and an eye-screw to attach
to the nose cone. There is a balsa sheet to cut out the four fins from and
single launch lug, which is cut in half to assemble.
The instructions are printed on 8 pages
(single-sided) of 8½ x 11" paper. There are color photos throughout
to assist in the assembly of the kit. There is also a fin template and tube
marking guide. The rocket is very easy to build and is probably not more than a
level 2 kit.
There are a couple of things that should be
pointed out in the build, otherwise, you are dealing with a very
straightforward model rocket with four fins and a nose cone.
tether is tied around one of the two thrust rings. This is done after a small
v-groove is cut into the thrust ring. This is a good technique because it
allows the thrust ring to fit nicely into the motor tube and prevents it from
showing (denting tube outward). This is usually less important if the motor
tube is smaller than the body tube, but in the case of the Flux Probe, the
motor tube IS the body tube.
The next step was a first for me. Not really
sure why the step is there, but it was described very well in the instructions.
That is to glue the second thrust ring onto the first to make a double-length
thrust ring with the Kevlar
sandwiched in-between. Perhaps Thrustline has determined that this protects the
The Flux Probe is not meant to be a person's
first rocket. Why not? Well, because in the next step a used motor casing is
needed! It is used to thread the Kevlar
back through and then the thrust ring assembly is glued and pushed into body
The 2" coupler makes the it easy to have
good alignment of the two body tubes. Thrustline does recommend rolling them on
a level surface to ensure they are straight.
The fins are cut out using the template. My
only complaint is that the template is regular notebook paper and it would be
nice to have it printed on cardstock. I find the notebook paper is too flexible
There is plenty of 3/32" balsa to cut
out the four fins. The instructions indicate which edges could be airfoiled,
but I chose not to. They are glued in place after using the wrap-around tube
The 1/4" elastic shock cord is tied to
and then attached to the eye-screw that has been installed into the balsa nose
cone. Then you choose (and I really like this) a parachute or a streamer. I
chose the streamer.
Thrustline does give finishing guidance
including using wood filler, priming, sanding, priming, sanding, then painting.
There are no decals provided with this kit.
I used my typical multiple coats of
Plastic-Kote Primer and sanding in-between. I then used Walmart Gloss Black
paint to finish it off (additional comments about Walmart
paint). I was going to add some prismatic paper on the fins, but just never
did (so far).
Overall, for CONSTRUCTION I
would rate this kit
½ points. The instructions are excellent. I personally don't mind
cutting out the fins myself, but would rather have a cardstock template verse a
notepaper one. A nice bonus to have both a parachute and a streamer provided.
The kit did not include any decals.
Thrustline recommends the B6-6 for the first
flight. They list the A8-5, B6-6 and C6-7 as recommended motors with altitudes
from 200 to 1000 feet.
Thrustline indicates the rocket should weigh
2.0 ounces. My rocket weighed in at 1.8 ounces. My CG was at 22" from the
Since this is a minimum-diameter rocket, the
motors are friction-fit with masking tape. Also, since this is a small
minimum-diameter rocket, it packing of the recovery system is difficult.
I decided to fly it for the first time on an
A8-5. After loading in two sheets (each tore in half) of wadding, struggling to
get the long elastic into the body tube and then sliding the rolled streamer on
top, it was ready to fly.
The flight was straight as an arrow. A8-5, no
way! The 5 is definitely too long of a delay. Perhaps I should have airfoiled
Also, the motor kicked out at the same time
as the nose cone ejected, then this rocket came in for a core-sample. Perhaps
this is why it is call a Flux Probe... probes into planets to take core samples
for analysis? Perhaps it was because the motor kicked out.
The second flight was on a C6-5. Didn't have
a C6-7, so thought it might eject early. However, after an straight liftoff it
had turned and ejected at apogee. The rocket fell fine (not in core-sample
position) until about 200 feet, then it lined up horizontally in the air and
fell the rest of the way. It too had kicked the motor out, but this time the
streamer was stuck exactly in half (the end had melted to the attachment
The third flight was on an A8-3 in our front
yard. Nice flight, could have used another second of delay. Motor kicked
(again) and it landed nicely. I had left the streamer stuck in half.
Fourth flight was on a B6-4 after unsticking
the streamer. Nice flight, but again needed extra on the delay. It recovered
fine, although I didn't see it land because it first bounced off our roof. No
damage. Oh, yeah, motor kicked out.
For FLIGHT/RECOVERY, I would
rate this rocket
points. The rocket is stable and will give you straight flights. I only
tested the streamer recovery which is all that I think the rocket needs. I'm
concerned that I could keep a motor from kicking out at ejection. I'm not new
at this, but I think the minimum diameter combined with the amount of stuff
Elastic and Streamer) that has to be stuffed in the top makes a lot of back
pressure. I would recommend wrapping tape around the bottom 1/4" of the
rocket body to the motor as well as the tape on the motor
I give the rocket an OVERALL rating of
½ points. It is a quick-to-build, steady performing rocket that is
good for small fields. The streamer or parachute would let the flier experiment
a bit. It does take some patience to get a nice finish with the balsa nose
cone, but then again, that how is was always done prior to plastic molds. I'm
going to produce a
Article on 18mm Longnecks and include this one. Watch for it.
Oh, I finally did get around to RockSIM'ing
it. Here are my results. Joe Policy's RockSIM shows it weighing 1.2 ounces, but
I think 1.8 (as mine did) to 2.0 (as Thrustline says) is closer after all is
said and done. The link to the RockSIM file above is mine. Joe's is in the
Click to see my 18mm Longneck comparison