How to Build a Multistage Model Rocket

To build a multistage model rocket, start from a manufacturer-designed two- or three-stage kit, fly only the certified commercial motor combinations its instructions list (a zero-delay booster such as an Estes B6-0 beneath a long-delay sustainer such as a C6-7), then weigh the finished airframe and simulate it in OpenRocket until the full stack and the sustainer alone each hold at least one caliber of stability margin. Size the launch field to the total installed impulse of every stage combined rather than the top motor. Under the National Association of Rocketry's Model Rocket Safety Code, a B6-0 plus a C6-7 is 15 newton-seconds, which requires a site 500 feet across. Fly it the first time at a club launch, where a range safety officer inspects the stack before it reaches the pad.

Two people reach that flight from opposite directions. One buys the kit and follows the printed motor list. The other draws an airframe, picks two motors that look compatible, and works out the rest afterward. That second route fails in a predictable place.

Three starting points, one flight

The difference is not skill. It is how much of the review someone else already did and signed.

| Starting point | Who proved the staging works | Motor pairing comes from | What you still have to prove | |---|---|---|---| | Manufacturer kit | Estes, before printing the instructions | The instruction sheet | That you built to the drawing and weighed it | | A kit you modified | Nobody, once mass or length changed | Void, the list assumed stock mass | Stability in both configurations, from measured mass | | Scratch design | You | Your own analysis against motor data sheets | All of the above, plus interface geometry and venting |

Estes catalogs two staged kits for a first attempt. The Mongoose (#2092) is a Skill Level 1 two-stage, 26.5 inches long, 2.3 ounces (65 grams) finished, projected to 1,600 feet on a C6-7. The Comanche-3 (#7245) is an expert-level three-stage, 41 inches, about 2.5 ounces, listed at 2,250 feet with a D12-0 first stage. Fly the Mongoose first, single-stage on an A8-3 before staging it. A first flight tests your gluing.

Why matching stages by motor letter fails

The designation looks like a specification. It is a bracket plus two measurements. The letter gives an impulse range in which each letter doubles the last: a B delivers up to 5 newton-seconds, a C up to 10, a D up to 20. The number after the letter is average thrust in newtons. The number after the dash is the delay in seconds before the ejection charge fires.

Watch what that does inside one family. Estes lists the C6-5 for a Mongoose flown single-stage and the C6-7 for the same airframe's upper stage. Same impulse, same 6-newton average thrust, two seconds apart, because a staged flight coasts longer before apogee and a short delay pops the parachute while the rocket is still climbing. The C6-0 shares that designation too, with no delay element and no ejection charge at all. Load a C6-7 where a C6-0 belongs and you get no staging plus an ejection charge fired into the stage above it.

Thrust separates them further. A C6 and a C11 both carry 10 newton-seconds. The C6 averages 6 newtons across a 1.6-second burn; the C11 averages 11 newtons across 0.8 seconds, peaking at 22.1 newtons against the C6's 15.3, so they leave the rod at different speeds. What governs the pairing is measured liftoff mass, the stability of each configuration, the booster's zero delay, and the combination the manufacturer tested.

Certified motors, and nothing you made yourself

The safety code puts this in one sentence: use only certified, commercially made model rocket motors, and do not tamper with them or use them for anything the manufacturer did not recommend. The NAR Standards and Testing Committee publishes the certified list, updated online and printed twice a year in Sport Rocketry. If a motor is not on it, no range safety officer will let it fly.

Searches for staged rockets tend to drift into fireworks territory. Do not follow. ATF's exemption at 27 CFR 555.141 covers motors holding no more than 62.5 grams of propellant, and exempts them from explosives licensing only. That is not authorization to fly something you mixed. State fire codes adopting NFPA 1122 are written around certified commercial motors. Drilling a delay or taping a nozzle voids the certification the whole code rests on.

Simulate both configurations, then weigh what you built

OpenRocket calculates stability margin as the distance between center of gravity and center of pressure divided by the body's reference diameter, expressed in calibers. Its documentation gives at least 1 caliber as the commonly recommended minimum, and above roughly 2 calibers the rocket weathercocks hard into wind. A staged design needs that check twice, because it is two rockets. Simulate the full stack leaving the rod, then the sustainer alone after separation, a shorter airframe with different fins and a different center of gravity.

Then weigh the thing. Estes lists 2.3 ounces for the Mongoose, and that describes the kit rather than your model, which also carries paint, glue fillets and tape. Put the finished rocket on a kitchen scale that reads grams, enter that number, and re-run. OpenRocket warns that its component analysis is static stability at one operating point, so plot the margin across the whole flight instead of reading one figure and stopping.

Every permit packet contains one blank box with stage fright: the number nobody measured because measuring it felt optional. I submitted a laundry conversion without the disconnect location, and it came back stamped. Measured mass is that box. A simulation run on a guessed weight is a drawing, and a drawing is not an approval.

Size the field to the whole stack, not the top motor

The Model Rocket Safety Code sizes the launch site by installed total impulse, meaning every motor you load, added together.

• A Mongoose flown single-stage on a C6-5 is 10 newton-seconds, inside the 5.01 to 10.00 band, needing a site 400 feet across.
• Staged on a B6-0 and a C6-7 it is 15 newton-seconds, in the 10.01 to 20.00 band, requiring 500 feet.
• A Comanche-3 on D12-0, C6-0 and C6-7 totals 40 newton-seconds, in the 20.01 to 40.00 band, requiring 1,000 feet.

Swapping that D12-0 for the smaller C11-0 gives 30 newton-seconds and buys nothing: same band, same 1,000 feet, roughly three American football fields end to end, cleared, with no dry grass near the pad.

The rest of the code applies at once. The rocket stays under 1,500 grams at liftoff, 125 grams of propellant and 320 newton-seconds total, with the rod within 30 degrees of vertical. Spectators stand at least 15 feet back for D motors or smaller and 30 feet for larger, though at a club launch the range safety officer sets that line. Wind at the field must be 20 miles per hour or less.

That last limit is measured at the field, not from a window. The heat outside mine has pressed the afternoon flat, a stillness that reads as perfect launch weather from a cool room. It is not information. Twenty miles per hour is a ceiling rather than a target.

Recovery drift decides how much field you actually need

Some arithmetic worth keeping: 10 miles per hour is about 14.7 feet per second, and a model rocket under parachute descends at roughly 11 to 15 feet per second. At those numbers it drifts about one foot sideways for every foot of altitude lost. Deploy at 1,600 feet in a 10 mph wind and expect a walk near 1,600 feet, more than three times the 500-foot minimum site that same flight requires. At the code's 20 mph ceiling, double it.

This is why the Comanche-3 carries dual streamers rather than parachutes from 2,250 feet, and why its spent boosters tumble instead of descending under canopy. Streamers drop faster and drift less. Estes offers three ways to shorten the walk: a spill hole cut in the canopy, which is permanent; shroud lines reefed with tape, which is reversible; or a streamer. Plan for two recovery points on a two-stage flight, three on a Comanche-3.

The stage interface

Classic Estes staging is direct. The booster motor's forward end is taped to the nozzle of the sustainer motor with a single layer of cellophane tape. When the booster's propellant is nearly gone, the top of the grain fractures and throws burning particles up into the sustainer nozzle. The tape holds the stages mated long enough for that to happen, then the sustainer's own flame melts it and the booster falls away. Cellophane rather than masking tape, because it melts at a lower temperature.

Masking tape has a different job, wrapped around each casing so the friction fit in its tube is genuinely tight. Check one thing before every staged flight: the nose cone should pull out more easily than the motor. Reverse that and the ejection charge blows the motor out the back with the parachute still packed.

Gap staging, where the motors do not touch, needs vent holes in the outer tube and the motor mount so booster gas escapes instead of pressurizing the space between stages. Without them the upper stage separates unlit.

Present it to a range safety officer

The National Association of Rocketry, founded in 1957, has more than 8,000 members and roughly 200 affiliated sections. The procedure at one of them is an intake counter with a launch rod at the end. You fill out a flight card, carry the rocket to safety check-in, and an officer inspects structural integrity, recovery system, motor retention, motor certification, and center of gravity against center of pressure. The range safety officer holds final authority over whether the model flies. Rejected means correct it and present it again, a resubmittal rather than a verdict.

Estes prints "suitable for ages 10 and older, with adult supervision for those under 12" on its standard motors, and that is the limit governing a black-powder two-stage. The under-18 restrictions people worry about, on reloadable motors, G motors and hybrids, belong to high power rocketry, reachable at 14 through NAR Junior High Power Certification. Sections expect minors to be accompanied, so read the club's visitor page before driving out.

Frequently asked questions

Can I legally build my own rocket?

Yes, and no federal permit is required. Under 14 CFR 101.22, a Class 1 model rocket carries no more than 125 grams of propellant, weighs under 1,500 grams including propellant, and uses paper, wood or breakable plastic with no substantial metal parts. Class 1 flights need no FAA notification.

Is it legal to make model rocket engines?

Not within model rocketry as the safety code defines it. The NAR Model Rocket Safety Code permits only certified, commercially made motors and forbids tampering. ATF exempts motors under 62.5 grams of propellant from explosives licensing, but that exemption covers licensing alone. State fire codes and club rules still require certified motors.

Are model rockets hard to build?

A single-stage kit is not. Estes rates the two-stage Mongoose as Skill Level 1, buildable in an afternoon with glue, sandpaper and paint. Staging raises the difficulty in preparation rather than construction: motor taping, friction fit, stability in two configurations, and a field large enough for the recovery walk.

Which Estes multistage rockets can I buy?

Estes catalogs the two-stage Mongoose (#2092, 26.5 inches, 2.3 ounces, Skill Level 1, 1,600 feet on a C6-7) and the three-stage Comanche-3 (#7245, 41 inches, about 2.5 ounces, expert level, 2,250 feet on a D12-0 first stage). Stock varies by retailer, so confirm availability before buying motors.

Which motors go in a two-stage model rocket?

The booster takes a zero-delay motor with no ejection charge, such as an Estes B6-0 or C6-0. The sustainer takes a long-delay motor, such as A8-5, B6-6 or C6-7. Use the exact combination printed in your kit's instructions, since the delay must cover a staged flight's longer coast.

Where can I launch a model rocket with someone supervising?

At a NAR section launch. The National Association of Rocketry has roughly 200 affiliated sections across the United States, each running sport launches with a range safety officer who inspects every rocket and holds final authority over whether it flies. Find your nearest section through the NAR club locator.