ESTES Model # 9720


During the mid-1950’s, the public concerns over nuclear fallout due to US and Russian testing was reaching a fevered pitch. To that end, President Eisenhower announced to the US on August 22, 1958, the US would ban further nuclear testing on or before October 31 of the same year. US scientists, wanting to gather as much data as possible, responded with Hardtack Series of tests. Scientists where interested in many scientific areas, but primary interest lay in the effects of radioactivity from underwater and above ground detonation.

The Hardtack Nuclear Testing Program consisted of 35 detonations in the Pacific Proving Grounds during the period of April-August 1958. Scientists, at the time, were chiefly concerned about damage to the ozone layer and possible effects of long-range radioactive fallout and determined that scientific measurements of the earth’s upper atmosphere (aeronomy) would help clarify what, if any, damage had occurred.

Single and two stage Doorknob rockets were developed using Lacrosse and Thiokol solid propellent motors and could launch an instrument laden sounding rocket to approximately 50 miles in altitude and capture radioactive data for analysis. Early results of this upper atmosphere data suggested little to no damage to the ozone layer was measured during the nuclear testing and water detonations probably produced enough ozone to replace what little might have been lost due to above ground testing.

The Estes 1:5.3 scale model Doorknob is big and impressive. Simple to build and fun to fly, this kit will be big hit in both the sport and scale rocket categories. This kit has two sets of decals available for those who want to turn this scale model into a sports model.

Additional Information

  • Length: 26.9″
  • Diameter: 3″
  • Weight: 10 oz.
  • Altitude: 1100′
  • Recovery: 18″ Parachute
  • Recommended Motors:
    • F15-4, F15-6, E16-4


Photo Gallery

Build History

  • 06/18/2020 – Purchased Estes Doorknob from Jon Rocket for $35.19 (Retail $39.99).
  • 07/07/2020 – Took measurements of components and recorded on page68 Book#4. Took pictures of package and components. Beveled leading edge of fins. Using green spacer at aft end of motor mount tube, glued solid centering ring and then removed spacer. Using fin as a spacer, glued slotted centering ring to motor mount tube. Glued green spacer on forward side of slotted centering ring.
  • 07/08/2020 – Glued motor mount assembly into body tube. Filleted rear centering ring joint. Glued launch lug 1/2″ and 10″ from aft end.
  • 07/10/2020 – Epoxied fins to body tube. Filleted fin joints
  • 07/11/2020 – Filleted forward centering ring joint. Cut out shock cord mount and glued shock cord to it. Glued inside forward end of body tube at least 2″. Placed clay into nose cone and tamped it in place.
  • 07/28/2021 – Spray painted with Flat red primer.
  • 02/28/2023 – Spray painted model with Rust-o-leum #328373 High Gloss White.
  • 04/28/2024 – Masked model for application of blue paint.
  • 04/29/2024 – Spray painted model with Rjust-oleum #327892 Gloss Brilliant Blue.
  • 04/30/2024 – Applied water slide and self-adhesive foil decals using instructions as guide. This completes construction of Ested #9720 Doorknob model rocket. Took pictures of finished model rocket.