Model Rocketry FAQ

This FAQ should answer most of your questions about Model Rocketry. See our other FAQ’s for more information. See our Engine page for an overview of the different types of hobby rocket motors.

Q. I have a child that is less than 9 years old. Is this too young for model rocketry?
A. Model rocket manufacturers all recommend adult supervision for young children (usually, those under 12). Many parents have had great success introducing these children to model rocketry.

Children under 10 or 11 do best in the hobby when a parent participates actively with them. Introduce them to simple, skill-level-1 kits with plastic fin units. Build yourself a rocket at the same time, then go out and fly them together.

Fly a range of motors. Go from 1/2A to A to B with a model to show kids the difference.

Q. What’s a good way to find other rocket enthusiasts in my area?
A. You just did. Come to one of our meetings or drop by a launch. We are always glad to see new people. Plus you will probably have a good time.

If you don’t live in the Tulsa, OK area, you can visit the NAR and/or Tripoli web sites. They have a list of local clubs.

Q. My flying field is so small I keep losing my rockets. What can I do?
A. Don’t get discouraged. Everyone loses rockets. It’s part of the hobby. There are ways to minimize this when you’re forced to fly in smaller fields, though. The following are some ideas:

Recovery Modifications:

  1. For smaller rockets, use a streamer instead of a parachute. This can be done with rockets of up to BT-50 body tube size and up to 18″ long. Be sure and check the rocket weight, though. If the model uses heavy plastic fins you might still want to use a parachute.
  2. Reef the chute lines to reduce the effective surface area. Tie or tape the shroud lines together 1/3 of the way from their end. This reduces the shroud lines to 2/3 of their original length and prevents the chute from fully opening. The rocket will come down faster and drift less.
  3. Cut out the Estes or Quest logo from the center of the chute. This lets more air spill through the chute and reduces its drag. Be careful to cut out the whole logo. Cutting only a small hole (say, less than 2″ in diameter) can improve the chute’s stability and actually make it lift better and drift further.
  4. Use a smaller chute. Try cutting down an 18″ chute to a 15″ chute, or a 12″ chute to a 10″ chute.
  5. Use longer ejection delays. If a B6-4 ejects the parachute right at apogee, use a B6-6 to let the rocket come down a little before popping the chute. The less time the chute is open equals less drift. Take care in making the chutes and recovery attachments extra strong, though, as the descending model will put more strain on the recovery system than if it were to deploy at apogee.

Other Suggestions:

  1. Find a different field. If you fly alone, try and find a local rocket club (like us). The odds are the club will have found a better field in which to fly.
  2. Fly larger rockets. A Big Bertha on a B6-2 will drift a lot less than a Sky Hook or other small model on a B6-4 or B6-6. Larger models have more impressive liftoffs, as well. Larger diameter rockets don’t fly as high and come down faster than the really small ones. The big ones are also easier to spot in high grass, weeds, trees, etc.
  3. Use smaller motors. If the recommended motors for a rocket are, for example, A8-3, B6-4 and C6-5 or C6-7, try it on A8-3’s first. If the model lands well within the recovery area you can then decide if the larger motors will allow the model to be retrieved.
  4. Launch rockets at a slight angle into the wind. The rockets will weathercock (turn and fly into the wind) and deploy recovery systems up wind. If all goes well, they will land closer to the launch site.

Q. I’ve seen designations like BT-20, BT-50, BT-55. What the heck do the numbers mean on Estes body tubes? Is their any special meaning in these numbers?
A. According to long time rocketeer, Peter Allway:

The Estes tube numbering seems to have progressed like the numbering of steps in a BASIC program. The very first Estes Catalog had numbers unlike the BT-20..BT-50… etc. system they use now. Sometime in the early 60’s they gave numbers 10, 20, 30, 40, 50 to their tubes in order of size. 10, 20, and 30 were almost identical in diameter (though 10 could be coaxed to fit into 30) All were meant to hold 18 mm rocket engines. BT-10 was an ultra-light spiral-wound mylar, BT-20 was essentially as it is today, and BT-30 was a parallel wound heavy-duty tube.

BT-40 was also a parallel wound heavy tube that fit over BT-20. (Rather like Quest T-20, but thicker and parallel wound.) BT-50 was as it is today, as was BT-60. BT-5 came along later, I believe created for the top of the Aerobee 300, and numbered halfway between 0 and 10. BT-55 came along after BT-60 and was numbered to fit in. PST-65 egg tubing came after the much larger BT-70 (originally used just for the Sprite tail ring) BT-100 and BT-101 first appeared in the 1/70 scale Saturn IB. BT-80 was created for the Saturn V.

It is interesting to note that two standard High Power Rocket diameters, 2.6″ and 4″ began as scale model components. Estes also created BT-3 for the Saturn IB, and BT-51 for the tanks. BT-52 was produced for the BT-60 Semi-Scale Saturn V, and this tube still appears as a hook-retaining sleeve on some Estes D engine mounts. The sleeves are still correct for a 1/242 Saturn V. Many BT-5 clone kits still use the length for an Aerobee 300.

Q. Is there any way I can buy model rocket kits, parts and engines at less than full retail?
A. A potential source for a large discount, if you are buying several hundred dollars worth of parts at one time, is America’s Hobby Center. They offer discounts of up to 40% off of Estes’ list price on orders of over $400.

There are several other mail order sources that sell at discount. Some of the smaller manufacturers/suppliers of model rocketry kits and supplies can sometimes offer a substantial bargain. Shop around. There are bargains to be found.

If you do a fair amount of flying, Estes sells a 24-pack of engines called the Flight Pack. It comes with 6 A8-3, 6 B6-4, 6 C6-5, 6 C6-7, recovery wadding and igniters. It generally retails between $32-36, which is less than the list price of the materials included. This can also be purchased at an additional discount from some mail order houses. Estes also sells ‘bulk packs’ of 24 A8-2 or B6-4 or C6-5 motors.

Quest motors have been recommended by some people. At the present time, they retail at less than the Estes equivalents. They can also be purchased direct from Quest ‘bagged’ in quantities of 10 or more. ‘A’ motors can get to less than $1 ea. when bought 50 or more at a time. ‘C’ motors get down to around $1.25.

You might also investigate your local club, if one is located convenient to you. Clubs sometimes arrange discounts with local hobby merchants. Several clubs also have at least one member selling parts and supplies at discount, mostly to the club members.

Q. Is it safe to use my old rocket engines from years ago?
A. I have properly stored engines from 1972 and 1975 that work just fine. But, if you suspect a set of motors may be bad, fire one by burying it in the ground pointing up with just the nozzle showing and use your launch system to ignite it as usual. Note: be sure and stand at least 15-20 feet away from the motor when you fire it.

Black powder motors tend to suffer reliability problems when they are temperature cycled. If you expose them to heat, by storing them in the attic, on your car’s dashboard, or in your metal range box in the hot sun on the launch field, you may have problems. These engines expand with the heat, but when they cool down, the propellant can separate from the cardboard casing inside. This causes the propellant to burn faster due to burning on the side. This generates more pressure than the motor was designed for which results in what we in the hobby call a “cato” or catastrophic failure.

Storing black powder motors in a damp basement can also cause problems when the humidity causes the compressed clay nozzle to soften and blow out when ignited. If you must store your motors in a damp/humid area, put them in a zip lock plastic bag, along with a silica gel packet if you have some.

Q. How can I tell the age of my Estes motors?
A. Estes uses a date code on their rocket motors. It’s of the form XXYZZ (example, 25T9) where the first number is the day of the month of manufacture, the letter is a code indicating year of manufacture, and the last number is the month (1 = January, 12 = December). Date codes run progressively through the alphabet, as follows:

T 1989
U 1990
V 1991
W 1992
X 1993
Y 1994
Z 1995
A 1996 – Estes cycled back to the beginning of the alphabet

In the early 70’s, Estes motors had the actual date stamped on them.

Q. Are the Aerotech composite motors the same size as Estes/MRC/Quest motors?
A. Aerotech makes the following ‘standard’ retail motors in -4 and -7 second delays. The first two motors are the same size as Estes A-C motors. The next two are the same size as Estes D motors. There are some other 24mm motors that are available from Aerotech that are longer than Estes D motors. Some of these ‘non-standard’ Aerotech 24mm motors are listed after the four ‘standard’ ones.

Motor Size Power Same Size As
D21 18x70mm 20NS Estes/Quest/MRC A-C
E25 18x70mm 22NS Estes/Quest/MRC A-C
E15 24x70mm 40NS Estes D motor
E30 24x70mm 40NS Estes D motor
F32 24x124mm 80NS Non-standard size
F44 24x101mm 70NS Non-standard size
G42 24x144mm 90NS Non-standard size
G55 24x177mm 125NS Non-standard size

Aerotech makes and sells reloadable motor casings and reloads in sizes from 18, 24, 29 mm and up. The 18mm is the size of an Estes C motor. The 24mm is the size of an Estes D or Aerotech E motor. The 29mm is the size of an Aerotech G motor.

Q. Can I use Aerotech or other composite motors in my Estes rockets?
A. Yes and no. Aerotech and Apogee Components make 18mm and 24mm composite motors. Composite motors have 2 to 3 times the power of comparably size BP motors (black powder motors). Balsa-finned 18mm powered models can start to loose body parts in quantity when launched with a D21 or E25 if they were not built strongly. The ejection charges seem to be hotter, as well. (At least in my experience.) The same holds true for Aerotech 24mm motors. Care should be taken before launching a 24mm-based model on an E15, let alone an E30. The Estes Saturn V flies well on E15’s. E30’s tend to shred all but the strongest D models, though. If I plan to use E’s in an Estes model, I make it a point to reinforce the motor mount, especially for EM-2060, EM-2070 and EM-5080 mounts. You also want to use an engine block (a 2050 adapter ring works great) in addition to the metal clip. It also would not be a bad idea to reinforce fin/body tube joints. Five minute epoxy fillets work great. Generous cyano fillets also seem to work well. White glued fins don’t seem to take E15/E30 launches with consistent success. Many modelers also recommend that stronger 24mm motor tubing, such as that from LOC or Aerotech, be used for models flying with composite motors. The stronger tubing holds up better to the ejection charges of the composites.

Q. Will my Estes launch system work with Aerotech composite motors?
A. The classic Estes, Quest and MRC 6 volt launch systems will not reliably ignite the Copperhead (TM) igniters that come with Aerotech motors, and Estes Solar Igniters (TM) will not ignite a composite motor. These motors need 12 volt systems for reliable ignition.

Q. Can I use Aerotech composite motors as boosters in my multi-stage rockets?
A. Basically, no. Black powder booster motors will not ignite composite motors. Therefore, you cannot use a composite upper stage in a traditional multi-stage, black powder rocket. Also, there are no composite booster motors currently in production. They all have delays (4 seconds being the shortest current delay from Aerotech, for example) or are plugged. Typically, you cannot (and should not) use these as boosters in standard black-powder multi-staged rockets.

If you want to use composite motors in multi-stage models then you have to use other methods of igniting the upper stage (whether black powder or composite) than are used with black-powder-only rockets. One method is to electronically ignite the upper stage motor using a mercury switch to complete an electrical connection to a capacitor at first stage burn-out. This, in turn, sets off a flash bulb/thermalite fuse combo (or electric match) which ignites the upper stage motor. Another method is to ignite lengths of thermalite fuse at the time the booster is ignited. The length of fuse determines the delay before the upper stage is ignited. The NCR High Power technical reports on staging composite motors is applicable to multi-staged, composite motor powered model rockets as well. However, thermalite and electric matches are regulated by the BATFE and require a license to purchase.

Portions of the FAQ were paraphrased from the RMR Newsgroup FAQ.