Richard Nakka's Experimental Rocketry Web Site

Xi Series of Rocket Launches

<EM> Xi</EM><EM> Xi</EM><EM> Xi</EM>

  • Introduction
  • Basic Description
  • Avionics
  • Recovery System
  • Rocket Motors
  • Drawings
  • Flights Summary
  • Launch Reports
  • Introduction

    Xi is my newest rocket project, which began in the late summer of 2017. After many successful flights of both the Zeta and DS rockets, it was felt that a rocket with a larger payload capacity was needed. The design of the Xi rocket was based on both the positive and negative experiences gained from the Zeta and DS series of flights. The objective was to incorporate the better features of the two predecessors in a larger size rocket that would allow for greater payload and for accommodating larger rocket motors.

    Basic Description

    The Xi rocket is largely of aluminum construction. The airframe is made of thin-walled (0.035 inch/0.89mm) aerospace grade aluminum tubing, of 3 inch (76mm) diameter for the forward section, and of 2.5 inch (64mm) for the aft section that houses the motor. A tapered coupler, machined from 6061 aluminum, joins the two body sections of different diameter. The coupler additionally serves to transfer thrust load from the motor to the rocket airframe. The four fins are fabricated of high-strength 2024-T3 sheet aluminum, bonded in place through slots cut into the body tube. The original conical nosecone (which houses the GPS transmitter) was machined from a single piece of Delrin thermoplastic. This was later replaced with a lightweight conical nosecone 3D printed using PLA plastic. In anticipation of higher speed flights, a 3D printed tangent-ogive nosecone was made and was first flown on Flight Xi-27. The avionics (recovery electronics) are housed within an Av-bay compartment which also serves as a coupler between aft and forward body sections. Additional payload can be accommodated in the Aft body section, which also houses an aft-facing video camera (not used for all flights).

    In addition to the nosecone, a number of Xi rocket parts are 3D printed, such as parachute piston (replacing earlier versions made of delrin or aluminum) and boattail (used on some flights). In all cases, PLA filament is used to produce the parts. Load testing has demonstrated that 3D printed PLA parts have appreciable strength, combined with excellent stiffness and surface hardness, well suited to rocketry applications. STL files for some of the 3D printed parts are given below.


    Based on overall positive experience with the Raven, this unit was chosen as the primary flight computer. The Raven measures and records flight data based on accelerometer and barometric readings throughout the entire flight. The Raven also activates main and backup pyro charges at apogee, and fires a pyro charge at a pre-determined altitude to release the parachute. Post-flight downloading of the Raven data provides altitude, axial and lateral acceleration, and velocity, as well as details regarding pyro charge activation. To ensure high reliability of safe recovery, triple redundancy is utilized. In addition to the Raven as the primary system for both apogee separation and parachute deployment, two additional flight computers are used as backup. The Eggtimer (Classic) and the BREO flight computer. For initial Xi flights the same backup Timer used on both Zeta and DS was used as the sole backup.

    The Raven, EggTimer and BREO are each separately powered by a 9V lithium primary cell battery. The main reason for choosing this battery is its excellent cold-weather performance. Recovery of the rocket after landing is greatly facilitated by use of a Big Red Bee (BRB) BRB900 GPS telemetry system. This system, also flown in the Zeta and DS rockets, consists of an on-board 250mw transmitter operating at 900 Mhz spectrum (no license required), which transmits GPS coordinates of the rocket throughout the flight and after landing. The signal is picked up by a matching receiver. The receiver has an LCD display showing the GPS coordinates. After landing, the GPS coordinates are entered into my Garmin hand-held GPS unit. The Garmin displays the distance to the downed rocket and direction, which makes tracking and recovery of the rocket a breeze.

    The BRB unit is mounted inside the nosecone, housed in a protective styrofoam shell. This shell additionally provides thermal insulation, a requirement for winter launches.

    Av-bay avionics, showing Raven and Eggtimer
    Av-bay avionics, showing Timer, control panel and 6G inertial switch
    Av-bay avionics, side view
    Av-bay avionics, side view
    Av-bay assembly, showing pyro charges and smoke canister
    Close-up of aft end of Avbay
    Big Red Bee GPS transmitter with styrofoam shell (opened)
    Big Red Bee GPS transmitter with styrofoam shell (closed)

    Recovery System

    Dual-deployment is used for recovery in order to minimize down-range drift of the rocket.The method is very similar to that of the DS rocket. At apogee, a pyro charge is fired which separates the rocket into two sections. The two sections, connected by a tether, then free-fall in a tumbling fashion, at a relatively slow velocity, typically around 70 feet/sec. (21 m/s). When a predetermined altitude is reached (typically 700 feet, or 215m.), a pyro charge is triggered by the flight computer which blows off the Av-bay compartment. The momentum pulls the recovery parachute out of the forward airframe. The pyro charges typically employ between 1 and 2 grams of Crimson Powder, contained within a sealed polyethylene tube.

    The Av-bay is secured to the airframe with two joints featuring nylon shear screws. The aft joint, which separates at the apogee event, is secured with three #4-40 nylon screws. The forward joint, which separates at the parachute deployment event is secured with six #6-32 flush-head nylon screws. The parachute originally used for recovery is the same as that used for Zeta flights, a 36" Fruity-Chutes semi-ellipsoidal chute. This was later replaced, starting at Xi-27, with a larger 40" chute. Descent rate under parachute is typically 20 feet/sec. (6 m/s).

    As mentioned, a primary and dual-backup system is employed for both the critical primary recovery event (separation at apogee) and parachute deployment event. The Raven flight computer fires a pyro charge at apogee. The Eggtimer and BREO likewise each fire a separate pyro charge at apogee. Parachute deployment has a single backup, the Eggtimer, which fires a separate pyro charge at an altitude of 500 feet (150m).

    Rocket motors

    It is expected that the Impulser-X motor will be used for most initial flights. Plans are in the works for flights powered by the new Helios-XX "I-class" motor powered by ANCP, which has a similar total impulse as Impulser-X. Another motor that is slated to loft the Xi rocket is the SSJ-F motor, a "J-class" motor that is the flight version of the SSJ motor that was used for static testing back in 2006-2007 timeframe. As a longer term goal, the Xi rocket will be utilized for flight testing of future APCP based rocket motors.


    Impulser-X rocket motor
    SSJ-F rocket motor (top) next to Impulser
    Rocket for Flight Xi-1
    Rocket for Flight Xi-2
    Cutaway view of Xi rocket
    AeroLab drawing of Xi rocket for Flight Xi-1


    Drawing ofXi rocket
    Aft section
    Av-bay body
    Av-bay body ring
    Parachute Piston (delrin)
    Parachute Piston (aluminum)
    Smoke Canister
    Electrical schematic of Xi backup timer
    Parts list for Xi backup timer

    STL files (3D printed parts)

    Conical nosecone
    Tangent-ogive nosecone
    Parachute piston
    Forward launch rail button
    Aft launch rail button
    C100-camera bracket
    CanPark Xtreme UHD camera bracket
    Aft-facing mirror fairing

    Flights Summary

            Nominal   Barometric Range    
    Flight       Impulse   Apogee      
    no. Launch Date Motor Propellant (N-s) Class ft. (m.)  [1] ft. (m.) Payload  [2] Note
    Xi-1 Nov.12, 2017 Impulser KNSB-S.1 356 I 1711 (521) 506 (154) Ra, SC, BRB, ABT, ET Maiden flight Xi rocket
    Xi-2 Dec.17, 2017 Impulser-X KNDX 449 I 2525 (769) 1266 (386) Ra, SC, BRB, ABT, ET, MC  
    Xi-3 Jan.7, 2018 Impulser-X KNDX 452 I 2959 (902) 1925 (587) Ra, SC, BRB, ABT, ET  
    Xi-4 Feb.19, 2018 Impulser-X KNDX 453 I 2591 (790) 413 (126) Ra, SC, BRB, ABT, ET, MC  
    Xi-5 Apr.7, 2018 Impulser-X KNDX 449 I 2478 (755) 1127 (344) Ra, SC, BRB, ABT, ET, MC, BR  
    Xi-6 Aug.15, 2018 Impulser KNSB 350 I 1833 (559) 500 (152) Ra, SC, BRB, ABT, ET, BR  
    Xi-7 Sept.12, 2018 Impulser-XX KNDX 559 I 3805 (1160) 1189 (362) Ra, SC, BRB, ET, BR, GY First flight with Impulser-XX motor
    Xi-8 Oct.21, 2018 Impulser-XX KNDX 547 I 3822 (1165) 673 (205) Ra, SC, BRB, ET, BR, GY  
    Xi-9 Nov.17, 2018 NTM-12 KNDX 354 I 1248 (380) 375 (114) Ra, BRB, ET, BR First flight with nozzleless motor
    Xi-10 Jan.5, 2019 Impulser-XX KNDX 544 I 3829 (1167) 1075 (328) Ra, SC, BRB, ET, BR  
    Xi-11 Feb.16, 2019 JEM KNDX 645 J 3901 (1189) 2224 (678) Ra, SC, BRB, ET, BR First flight with JEM motor
    Xi-12 June 6, 2019 JEM KNDX 463 I 3507 (1069) 339 (103) Ra, SC, BRB, ET, BR  
    Xi-13 Aug. 16, 2019 JEM KNDX 586 I 4584 (1397) 1952 (595) Ra, SC, BRB, ET, BR  
    Xi-14 Sept.28, 2019 JEM KNDX 610 I 3989 (1216) 1178 (359) Ra, SC, BRB, ET, BR, mC Auxilliary chute mounted camera
    Xi-15 Dec.22, 2019 JEM KNDX 614 I 3933 (1199) 1962 (598) Ra, SC, BRB, ET, BR  
    Xi-16 Feb.16, 2020 Impulser-XX KNDX 504 I 3338 (1018) 1552 (473) Ra, SC, BRB, ET, BR  
    Xi-17 Mar.14, 2020 APM-C KNPSB 460 I 2978 (908) 2253 (688) Ra, SC, BRB, ET, BR First flight with KNPSB propellant
    Xi-18 June 20, 2020 Impulser-B KNSB/KNPSB 423 I 2448 (746) 1374 (419) Ra, SC, BRB, ET, BR, SL First flight of Impulser-B; Test of strobe lamp
    Xi-19 Aug. 29, 2020 APM-C.2 KNPSB 482 I 3271 (997) 856 (261) Ra, SC, BRB, ET, BR, mC First flight of APM-C.2 motor
    Xi-20 Oct.10, 2020 APM-D.1 APX-N1.0 469 I 2949 (899) 1325 (404) Ra, SC, BRB, ET, BR First-ever flight powered by APCP
    Xi-21 Nov.28, 2020 APM-G KNPSB 687 J 4471 (1362) 3521 (1073) Ra, SC, BRB, ET, BR First flight of finned APM-G motor
    Xi-22 Feb.20, 2021 APM-D.1 APX-N1.0 493 I 2106 (642) 221 (67) Ra, SC, BRB, ET, BR, MC Liftoff-initiated smoke charge
    Xi-23 Mar.20, 2021 Loki 54 KNSB 436 I 2165 (660) 1095 (333) Ra, SC, BRB, ET, BR, MC Loki 54 is a commercial HPR motor
    Xi-24 June 26, 2021 APM-C.3 KNPSB 482 I 2766 (843) 287 (88) Ra, SC, BRB, ET, BR, MC  
    Xi-25 Aug.14, 2021 APM-E.2 AXP-AP2.4 505 I 2830 (863) 725 (221) Ra, SC, BRB, ET, BR, MC First flight of epoxy-based APCP.
    Xi-26 Sept.18, 2021 APM-G KNPSB 449 I 266 (81) 264 ( 80) Ra, SC, BRB, ET, BR, MC Motor CATO shortly  after liftoff
    Xi-27 Dec.11, 2021 APM-E.3 AXP-AP2.4 682 J 3601 (1098) 2101 (640) Ra, SC, BRB, ET, BR, MC  
    Xi-28 Mar.26, 2022 APM-C.4 KNPSB 593 I 3061 (933) 1783 (544) Ra, SC, BRB, ET, BR, MC  
    Xi-29 July 29, 2022 Impulser KNSB 395 I 1968 (600) 574 (175) Ra, SC, BRB, ET, BR, MC Impulser motor stretched to increase capacity.
    Xi-30 Aug.13, 2022 APM-E.6 AXP-AP4.1 689 J 4866 (1483) 481 (147) Ra, SC, BRB, ET, BR Highest apogee of any Xi, Zeta or DS flight
    Xi-31 Nov.19, 2022 APM-E.12 AXP-AP6.1 645 J 3536 (1078) 2618 (798) Ra, SC, BRB, BR, BR, MC  
    Xi-32 Dec.3, 2022 APM-E.14 AXP-AP4.7 690 J 3806 (1160) 484 (148) Ra, SC, BRB, BR, BR, MC Drogue chute deployment at apogee
    Xi-33 Jan.14, 2023 APM-E.14 AXP-AP4.7 690 J 3783 (1153) 122 (37) Ra, SC, BRB, BR, BR, MC  
    Xi-34 Mar.25, 2023 APM-E.14 AXP-AP4.7 721 J 3926 (1197) 1781 (543) Ra, SC, BRB, BR, BR, MC Successful drogue chute deployment
    Xi-35 June 3, 2023 APM-J.2 AXP-AP7.2 842 J 5020 (1530) 103 (32) Ra, SC, BRB, BR, BR, MC Highest impulse motor and apogee to date
    Xi-36 Aug. 26, 2023 JEM KNDX 593 J 1233 (376) 816 (249) Ra4, Ra, BR, SC, BRB, MC Motor bulkhead suffered burn through
    Xi-37 Jan. 27, 2024 APM-E.14 AXP-AP4.7 685 J 3970 (1210)) 797 (243) Ra4, Ra, BR, SC, BRB, MC  
    [1] Barometric altitude per Raven, corrected for base temperature
    [2] Payload definitions:
    Ra = Raven3 flight computer
    Ra4 = Raven4 flight computer
    MC = mini camcorder (on-board)
    mC = micro camcorder (out-board)
    SC = Smoke Charge
    SL = Strobe Lamp
    BRB = BRB900 GPS transmitter
    ABT = Apogee Backup Timer
    ET = Eggtimer flight computer
    BR = BREO-N flight computer
    GY = Gyro sensor module

    Launch Reports