# Air-Launch Experiment Using Suspended Rail Launcher for Rockoon

^{1}

^{2}

^{3}

^{4}

^{5}

^{*}

## Abstract

**:**

## 1. Introduction

_{2}O propellant is suitable for a high-altitude rockoon, because N

_{2}O can be stored in liquid state at the temperature of the atmosphere, preventing the heat conduction through the tank wall. The tank pressure decreases as the propellant is cooled by the atmosphere. The lower limit is 0.7 MPa, that is, the saturation pressure at the air temperature at 20 km of altitude. It is too low for self-pressurized feeding; therefore, a small battery-powered turbopump is also under development at CIT. The recent progress in low-cost hybrid rocket propulsion will accelerate the long-lasting development of rockoon systems because the non-combustible nature of hybrid rockets provides a significant advantage in terms of safety, with respect to the balloon or launcher accidentally falling. However, the aforementioned issues related to the attitude of the launcher have never been addressed.

## 2. Experiment

## 3. Experimental Results

#### 3.1. Attitude Controller Unit Test

#### 3.2. Air-Launch Trajectory

#### 3.3. Launcher Attitude

## 4. Discussion

#### 4.1. Double Pendulum Model

#### 4.2. Elevation Angle Dynamics

#### 4.3. Parameter Study

## 5. Conclusions

- The azimuth angles of the impact points were within the range of $8\xb0\text{}$ with respect to the target azimuth angle.
- The fluctuation of the elevation angle was observed due to the thrust misalignment and friction force between the rocket and rail. The launcher elevation angle should be determined considering these effects for accurate trajectory predictions.

- Rail lubrication is necessary to minimize variation in the friction coefficient.
- Thrust misalignment is the most significant cause of elevation fluctuation and also causes azimuthal error.
- There is a tradeoff between the leaving velocity and variations in the elevation angle and its rate when the rocket leaves the rail. The optimum length should be selected to minimize the trajectory error.

## Supplementary Materials

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## Nomenclature

$\omega $ | angular velocity of gyroscope wheels |

$\theta $ | tilted angle of gyroscope wheel axis |

${I}_{\mathrm{d}}$ | moment of inertia of the gyroscope rotor assembly |

${I}_{\mathrm{L}}$ | moment of inertia of the launcher |

$L$ | vertical component of the change in angular momentum of each gyroscope wheel |

$\Omega $ | increase in the rotation speed of gyroscope |

$M$ | torque generated by CMG |

$l$ | length of crane wire above the hook |

${l}_{1}$ | length of wire under the hook |

${l}_{2}$ | distance between the top and the center of gravity of the rod |

${f}_{1}$, ${f}_{2}$ | eigenfrequencies of the 1st and 2nd modes |

${\omega}_{1}$, ${\omega}_{2}$ | angular eigenfrequencies of the 1st and 2nd modes |

${\theta}_{1},{\theta}_{2}$ | fluctuation angles from the equilibrium attitude |

$m$ | mass of rod |

$I$ | moment of inertia of rod |

$\epsilon $ | target elevation angle |

$\delta $ | thrust misalignment angle |

${m}_{\mathrm{r}}$ | mass of rocket |

${I}_{\mathrm{r}}$ | moment of inertia of rocket |

$F,\text{}F$ | friction force vector, and its magnitude |

$T,\text{}T$ | thrust force vector, and its magnitude |

$D$ | D’Alembert’s inertial force vector |

${a}_{\mathrm{r}}$ | acceleration of rocket |

$\mu $ | friction coefficient |

${I}_{\mathrm{c}}$ | combined moment of inertia |

$x,y$ | horizontal and vertical locations of center of gravity (CG) |

${r}_{\mathrm{T}}$ | location vectors of the engine nozzle from combined center of gravity (CCG). |

${r}_{\mathrm{R}}$ | location vectors CG of the rocket from CCG. |

## References

- Inatani, Y.; Ohtsuka, H. SS-520 Nano satellite launcher and its flight result. In Proceedings of the 32nd Annual AIAA/USU Conference on Small Satellites, Logan, UT, USA, 4–9 August 2018; p. SSC18-IX–03. [Google Scholar]
- Ito, T.; Yamamoto, T.; Nakamura, T.; Habu, H.; Ohtsuka, H. Sounding rocket SS-520 as a CubeSat launch vehicle. Acta Astronaut.
**2020**, 170, 206–223. [Google Scholar] [CrossRef] - Sarigul-Klijn, N.; Sarigul-Klijn, M.; Noel, C. Air-launching earth to orbit: Effects of launch conditions and vehicle aerodynamics. J. Spacecr. Rocket.
**2005**, 42, 569–572. [Google Scholar] [CrossRef] - Okninski, A.; Raurell, D.S.; Mitre, A.R. Feasibility of a low-cost sounding rockoon platform. Acta Astronaut.
**2016**, 127, 335–344. [Google Scholar] [CrossRef] - Kelly, J.W.; Rogers, C.E.; Brierly, G.T.; Martin, J.C.; Murphy, M.G. Motivation for air-launch: Past, present, and future. In Proceedings of the AIAA SPACE and Astronautics Forum and Exposition, Orlando, FL, USA, 12–14 September 2017; p. AIAA 2017-5231. [Google Scholar]
- Ketsdever, A.D.; Young, M.P.; Mossman, J.B.; Pancotti, A.P. Overview of advanced concepts for space access. J. Spacecr. Rocket.
**2010**, 47, 238–250. [Google Scholar] [CrossRef] - Itokawa, H. The Japanese Sounding Rockets. J. Jet Propuls.
**1957**, 27. [Google Scholar] [CrossRef] - JP Aerospace Rockoons. Available online: http://www.jpaerospace.com/rockoons.html (accessed on 10 January 2021).
- Strange, M. In Flight Launch Vehicle. Available online: https://scholarworks.calstate.edu/downloads/2n49t2733 (accessed on 10 January 2021).
- Dougherty, K. Upper atmospheric research at Woomera: The Australian-built sounding rockets. Acta Astronaut.
**2006**, 59, 54–67. [Google Scholar] [CrossRef] - Johnson, I.; Roberson, R.; Truitt, C.; Waldock, J.; Northway, P.; Pfaff, M.; Winglee, R. Development of a Rockoon Launch Platform and a Sulfur Fuel Pulsed Plasma Thruster CubeSAT. In Proceedings of the AIAA/USU Conference on Small Satellites, Logan, UT, USA, 4–7 August 2014; pp. 1–8. [Google Scholar]
- Gómez, B.U.; Illescas, A.N.; Moreno, D.P.; Reina, A.R.; Raurell, D.S. LEEM Rockoon project: Developing a high altitude platform. In Proceedings of the International Astronautical Congress, IAC, Jerusalem, Israel, 12–16 October 2015; Volume 11, pp. 8922–8930. [Google Scholar]
- Inatani, Y.; Akiba, R.; Hinada, M.; Nagatomo, M. Atmospheric reentry flight test of winged space vehicle. In Proceedings of the AlAA 4th International Aerospace Planes Conference, Orlando, FL, USA, 1–4 December 1992. [Google Scholar]
- Yuji, S.; Kanazawa, T.; Yasuhiro, S.; Takahashi, Y.; Yoshida, K.; Taguchi, M. Dynamic Modeling and Experimental Verification of the Pointing Technology in Balloon-Borne Telescope System for Optical Remote Sensing of Planets. Trans. Jpn. Soc. Aeronaut. Space Sci. Space Technol. Jpn.
**2009**, 7, Pd_23–Pd_28. [Google Scholar] [CrossRef] [Green Version] - Shoji, Y.; Kitamura, K.; Yamada, K. A Low-Cost Azimuthal Control Method for Stratospheric Balloon Gondolas. Trans. Jpn. Soc. Aeronaut. Sp. Sci. Aerosp. Technol. Jpn.
**2018**, 16, 644–650. [Google Scholar] [CrossRef] - Kassarian, E.; Sanfedino, F.; Alazard, D.; Evain, H.; Montel, J. Modeling and stability of balloon-borne gondolas with coupled pendulum-torsion dynamics. Aerosp. Sci. Technol.
**2021**, 112, 106607. [Google Scholar] [CrossRef] - Shoyama, T.; Wada, Y.; Matsui, T. Conceptual Study on Low-Melting-Point Thermoplastic Fuel/N
_{2}O Hybrid Rockoon. J. Spacecr. Rocket.**2021**, in press. [Google Scholar] [CrossRef] - Gemignani, M.; Marcuccio, S. Dynamic characterization of a high-altitude balloon during a flight campaign for the detection of ISM radio background in the stratosphere. Aerospace
**2021**, 8, 21. [Google Scholar] [CrossRef] - Wikipedia Friction. Available online: https://en.wikipedia.org/wiki/Friction (accessed on 17 June 2021).

**Figure 6.**Double pendulum model of the suspended launcher. When the launcher is settled at the equilibrium state, ${\theta}_{1}={\theta}_{2}=0$.

**Figure 8.**Double pendulum model of the suspended launcher with moving rocket. Red and blue arrows are acting on the launcher and rocket, respectively. The misalignment angle $\delta $ is highly exaggerated.

Before Ignition | After Ignition | |||||
---|---|---|---|---|---|---|

Mass (launcher + rocket) | $m$ | kg | 14.0 | 12.8 | ||

Moment of inertia | $I$ | kg m^{2} | 4.67 | 2.96 | ||

Actual | Adjusted | Actual | Adjusted | |||

Length of the wire | ${l}_{1}$ | m | 0.357 | 0.950 | 0.357 | 0.950 |

Distance of the CG | ${l}_{2}$ | m | 0.483 | $\leftarrow $ | 0.378 | $\leftarrow $ |

1st mode frequency | ${\omega}_{1}$ | Hz | 0.43 | 0.38 | 0.46 | 0.40 |

Mode shape | ${\mathsf{\Theta}}_{1}/{\mathsf{\Theta}}_{2}$ | - | 0.49 | 0.60 | 0.47 | 0.61 |

2nd mode frequency | ${\omega}_{2}$ | Hz | 1.16 | 0.81 | 1.15 | 0.82 |

Mode shape | ${\mathsf{\Theta}}_{1}/{\mathsf{\Theta}}_{2}$ | - | −2.78 | −0.84 | −2.25 | −0.65 |

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. |

© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Shoyama, T.; Banno, A.; Furuta, Y.; Kurata, N.; Ode, D.; Wada, Y.; Matsui, T.
Air-Launch Experiment Using Suspended Rail Launcher for Rockoon. *Aerospace* **2021**, *8*, 289.
https://doi.org/10.3390/aerospace8100289

**AMA Style**

Shoyama T, Banno A, Furuta Y, Kurata N, Ode D, Wada Y, Matsui T.
Air-Launch Experiment Using Suspended Rail Launcher for Rockoon. *Aerospace*. 2021; 8(10):289.
https://doi.org/10.3390/aerospace8100289

**Chicago/Turabian Style**

Shoyama, Tadayoshi, Ayana Banno, Yousuke Furuta, Noboru Kurata, Daisuke Ode, Yutaka Wada, and Takafumi Matsui.
2021. "Air-Launch Experiment Using Suspended Rail Launcher for Rockoon" *Aerospace* 8, no. 10: 289.
https://doi.org/10.3390/aerospace8100289