Slow lift-off, with a nice thick column of white smoke

Estes Motors - E9-4

  • Part Number (PN): 05761
  • Qty per pack: 3 motors
  • Size: 24mm Single use
  • Burn Time: 3.1 sec
  • Total Impulse: 28.5 Newton-seconds
  • Motor Length: 95 mm
  • Max Thrust: 19.5 Newtons
  • Total Mass: 64.1 g
  • Propellant Mass: 35.8 g
  • Manufactured by: Estes
  • $25.67
    Product is in Stock (10+)

    The E9-4 is a motors for lightweight rockets. It uses black powder propellant, so it is easy to ignite, and it has that classic sound that you love when an Estes motor takes off. Great for clustering!
    Required to ship HAZMAT. More Info.
    Estes Black Powder Motors

    Estes Industries makes a variety of different motors and sizes. The ones shown here are Black Powder propellant. Black powder is also called gun powder, and has only three ingredients: charcoal, potasium nitrate, and sulfur. The advantage of black powder propellant is that it is cheaper compared to more exotic propellants. The downside is that it doesn't create a lot of energy per kilogram of fuel. The easy way to tell a black powder motor from other motors, is that it comes in a paper casing. That is one reason it is so inexpensive compared to other fuels.

    There are different size black powder motors, as shown in the picture below. For reference, the typical model rocket engine that comes with most starter sets, is the 18mm diameter X 70mm long variety (shown 2nd from the left). If you want more power, you'd probably select a bigger motor, and if you have a small launch field, you might want to choose a motor with less power.

    Do You Need Help Choosing A Rocket Motor?

    Don't panic! We're here to help you.

    1. First off, take a look at your kit. Are there recommendations on the packaging?
    2. If you purchased the kit from us, or if you purchased a kit that we also sell, take a look at the recommendations on the kit's page. It's near the bottom.
    3. If your field is limited and surrounded by trees and buildings, choose a motor with a lower letter and number to limit altitude and increase your chance of recovery.

    If you're still unsure about which motor to use, don't hesitate to call us at 719-535-9335 and ask for our recommendations. We're warm and friendly, and don't bite (that's a promise).

    >What is a "Single-Use" Motor and Why Should I Use One?

    The motors listed on this page are all "Single Use," which means they can only be used once and then the entire thing, casing and all, is discarded. We also offer "reloadable motors" in which the casing can be cleaned out and used over and over.

    What are the advantages of single-use motors?

    1. They are simple and reliable. Just put the motor into the rocket and launch it!
    2. They're readily available and, in an emergency, you can pick some brands up at local hobby shops.
    3. Fastest turn-around times between flights of the same rocket means you can get a ton of flights done in the same day!
    4. If you lose your rocket due to wind, extreme altitude or other, you're not out the investment of the much more expensive reloadable casing.
    5. Safer to use by younger children, as the propellant and ejection charge are all sealed within the casing.

    What is the disadvantage of single-use motors?

    1. Single-use motors cost a little more per-flight than reloadable.
    2. Larger single use motors, particularly with E class or higher, you often have to pay a HAZMAT fee, which can cause shipping to be upwards of $45. This is because only so much propellant can be in a continuous chunk before there is an assumed risk. Any motors that require the fee are marked.

    You have to weigh the advantages versus the extra cost. We believe that there are a lot of cases where it makes sense to use them, which is why we carry so many different ones.

    Flight Characteristics of These Motors:
    From a building standpoint, this model is quite easy. It uses the traditional construction techniques you are familiar with from building smaller model rockets. And the instructions are absolutely phenomenal; there are lots of excellent illustrations that clarify the text.

    Note: While the illustrations are superb, we still recommend actually reading the written portion of the instructions. You'll pick up a lot of new building tips that can be used on other rockets.

    13mm diameter "Mini-motors" (these are designated by the "T" at the end of the motor name). These motors fit into the Apogee 13mm diameter Airframe Tube (Part Number 10062).


    First off, this motor is a "mini" size, which means it is 13mm in diameter. It is intended for relatively small rocket kits. It will work in the Apogee SR-72 Darkbird, and the Texas Twister kits. The 1/2A motor won't loft either of these models very high, because it doesn't have a lot of thrust. This could be an advantage for the first flight of both models; since you don't want either of them to go very high on the first launch. Otherwise, they could be caught by a gust of wind and drift away. You want to be able to get them back so you can fly them again, don't you?

    Another use for this motor is when you want to video tape, or photograph the descent of the models. Since they don't go so high, you'll have a much better chance of being able to capture an image of the model in flight. For both the Texas Twister, and the SR-72 Darkbird, which have unique recovery features, this is the motor you'd want to use.

    The 1/2A3-2T motor is a quick burning motor. Since it is small, it doesn't make much of a roar on lift-off. It is more of a pfffffsss sound. But that OK, isn't it. Some times, when you have small children that have never seen a launch before, you don't want to scare them the first time with a loud roaring motor like the D12. So this could be used to acclimate the kids and get them used to seeing a rocket take off. Then you can start launching those bigger rocket motors that make a lot more noise.


    This motor is the same size as the 1/2A3-2T listed previously. But it has almost twice the propellant mass, and burns much much longer than the 1/2A variety. So it will push the rocket significantly higher into the air. How much higher? That is difficult to guess at. I recommend that you run Rocksim flight simulations to see the altitude difference.

    What do all the letters and numbers in the the motor name mean?

    Lets take an example so you can see how to read the charts. As an example, we'll look at the "1/2A3-2T" motor. 

    Breaking it down, we have four bits of information. "1/2A," "3," "2," and "T"

    Power ClassificationThe first letter, "1/2A," in our example, is the power level classification of the motor.  The "1/2" power band, as the chart to the right shows, is greater than .625 Newton-seconds of Total Impulse, and less than 1.25 Newton-Seconds. The maximum power doubles from one letter to the next. So a "B" motor can have twice the power of a "A" motor; which means it will fly approximately twice as high.

    Remember, think of power as the size of the fuel tank. The tank doesn't have to be totally full. So An "E" motor isn't required to have the maximum of 40 N-s of total power to still be classified as an "E". It just has to have greater than 20 N-s but less than 40 N-s. This gives us the power-bands (shown as the colors in the chart to the right).

    The first number after the power letter is the average thrust level of the rocket measured in Newtons, equivalent to 0.225 pounds of force. That means in our example, the motor has an average thrust of 3 Newtons during the entire burn time. If you were driving a car, you could relate average thrust to the amount of pressure you push on the accelerator pedal. The harder you push, the higher the average thrust of the motor, and hence the higher you'll accelerate the rocket. If you want to go fast, choose a high thrust motor. If you want to get good economy (longer travel distance), choose a lower average thrust motor. 

    For example, a B6 and a B4 would have the same amount of fuel in the tank. But the B6 burns it faster, and hence the rocket will reach a higher speed. The B4 motor burns the fuel slower, and like in your automobile, you'll get more distance out of the fuel that is burne

    The number after the dash is the length of time in which the "delay" charge burns before it allows the ejection charge, which deploys your parachute, to go off. Delay allows time for the rocket to coast and slow down so the parachute doesn't rip out of the tube at ejection. In our example, the rocket would coast for 2 seconds before deployment.

    Most single-use motors give a hard number for the delay, and you will need to purchase the appropriate one for your kit. Some loadable, larger single use or reloadable motors will often have a maximum delay that, with a specially designed tool, you can use to shorten the delay to what is best for your rocket. Look at the "Max Delay" statistic for that particular motor.  If it is an N/A, or not listed, you cannot adjust the delay.

    For black powder motors, the letter after the delay time is meaningless. Estes put the "T" designation to refer to "tiny." When Estes first produced the "T" size motors, they only had two sizes. At this point in time, the "T" just causes confusion, because a letter is used on composite and high-power motors to designate the type of propellant and the color of the flame produced by the motor. Since these are black powder motors, a letter isn't really needed. The "T" size motor are sometimes referred to as Estes mini-motors.

    Engine Diameter and Length

    Unfortunately, the engine diameter and length are not included in the type code printed on the side of the rocket. So before you can pick an engine from the charts, you have to refer back to the rocket kit itself, and see which engine diameter it can use. Do that first. Most kits can accept different length motors, so that is not an issue. The most important thing when selecting a rocket engine is the diameter, and then the "type" designation.

    How to use the Sortable Table Below:

    Click the "Select Comparison Columns" button to hide or show information. Click the headers to sort up or down. Click the subheader to filter the table to include just the information you want.

    Not All Data Shown. Expand your browser or select options above.

    Motor Comparison: Estes 24mm Propellant for none casings.
    Motor P/N Manuf & Type/ Casing Delay
    Color Burn Time Tot. Imp.
    Max Thrst
    Init. Mass
    Prop. Mass
    Price Buy Now!
    05761 Estes Single Use N/A -- 3.1 28.5 19.5 95 64.1 35.8
    (HAZ)3 pack
    05762 Estes Single Use N/A -- 3.1 28.5 19.5 95 64.8 35.8
    (HAZ)3 pack
    05763 Estes Single Use N/A -- 3.1 28.5 19.5 95 64.9 35.8
    (HAZ)3 pack
    05764 Estes Single Use N/A -- 0.8 8.8 21.7 70 34.5 12.0
    3 pack
    05765 Estes Single Use N/A -- 0.8 9.0 21.7 70 35.7 12.0
    2 pack
    05766 Estes Single Use N/A -- 0.8 9.0 21.7 70 35.5 12.0
    2 pack
    05767 Estes Single Use N/A -- 0.8 9.0 21.7 70 35.7 12.0
    3 pack
    05780 Estes Single Use N/A -- 1.7 16.8 29.7 70 39.2 21.1
    2 pack
    05781 Estes Single Use N/A -- 1.7 16.8 29.7 70 41.4 21.1
    2 pack
    05782 Estes Single Use N/A -- 1.7 16.8 29.7 70 45.2 21.1
    2 pack
    05783 Estes Single Use N/A -- 1.7 16.8 29.7 70 44.9 21.1
    2 pack
    05784 Estes Single Use N/A -- 2.4 27.2 33.3 95 52.6 35.9
    (HAZ)3 pack
    05785 Estes Single Use N/A -- 2.4 27.2 33.3 95 58.5 35.9
    (HAZ)3 pack
    05786 Estes Single Use N/A -- 2.4 27.2 33.3 95 59.9 35.9
    (HAZ)3 pack
    05787 Estes Single Use N/A -- 2.4 27.2 33.3 95 57.9 35.9
    (HAZ)3 pack
    Sorry... We do NOT ship rocket engines outside the USA.
    Please be aware that typical shipping transit times for motors are 1-2 weeks.
    • Propellant Type descriptions are listed below on this page. Click here to jump down now.

    • N/A: Non-adjustable delay. Single Use motors are sold with a variety of delays built-in.

    Note: These motors (HAZ) are shipped with a HAZMAT fee of $28 on top of the standard UPS/FedEx ground shipping costs. (Learn More about HAZMAT Fees). These motors are non-returnable due to shipping regulations.

    Frequently Asked Questions about the Estes Motors - E9-4
    Q:Why don't you ship rocket motors to countries outside the USA?
    A: There are too many shipping regulations. We're a small company, and we don't have the manpower to track the regulations for each country in the world. So to keep our prices as low as possible, we only ship to USA customers.

    Q:Will the Aerotech First Fire Jr.™ igniters work in these motors?
    A: NO. They are too big to fit into the nozzle hole. They are better for bigger size motors. The Estes Sonic or the Quest Q2G2 are best for replacing any lost or fizzled igniters.

    Q:Can you ship this item to me by this weekend?
    A: All motors (including kits that contain rocket motors) must be shipped by surface transportation (truck). While we usually ship this item the same day the order comes in, you should plan extra time for the postal service to deliver them via third class mail (Parcel Select).

    To expedite your order, you can request that the order be split, and the motors ship separately from the rest. This will incur a fee of $6 for standard motor shipping (not hazmat) to cover the additional cost of two shipments.

    Q:How do you find the Maximum Weight a rocket motor can lift?
    A: Click Here to read the article that explains how "Manufacturer's Recommend Lift-Off Weight" is determined.

    Q:How is maximum lift-off weight determined?
    A: The maximum recommended lift-off weight for each delay depends on the size of the rocket, its drag coefficient, launch angle, and the wind conditions at launch. We recommend running a RockSim computer simulation for each rocket design and launch conditions to select the proper motor delay. For help selecting the correct delay time, see Apogee Technical Publication #28. For additional information on maximum lift-off weight, see our FREE newsletter article on this subject. Click here to download Issue #214.

    Learn how to select rocket motors
    Q:I need help selecting motors. What should I do? Can you teach me how to select them myself?
    A: Watch this YouTube video - How to Select Model Rocket Engines

    We encourage you to learn the proper motor selection technique. Please watch our YouTube video that will walk you step-by-step through the process

    Reviews for the Estes Motors - E9-4

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