Effect of Water and Humidity on Hypergolic Propellant Ignition Delay
improves MMH ignition delay time and water concentration shows no effect
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- I. Introduction
| improves MMH ignition delay time and water concentration shows no effect. Nomenclature c* = characteristic velocity IDT = ignition delay time I sp = specific impulse MMH = monomethylhydrazine NTO = dinitrogen tetroxide PTFE = polytetrafluoroethylene RFNA = red fuming nitric acid RH = relative humidity TEAB = triethylamine borane WFNA = white fuming nitric acid 𝜖 = expansion area ratio = density I. Introduction n American rocketry, monomethylhydrazine (MMH) and dinitrogen tetraoxide (NTO) are the paradigm of success for storable, hypergolic, liquid bi-propellants. The equilibrium specific impulse (I sp ), 330 s assuming a 1000 psia chamber pressure perfectly expanded with an area ratio of 50, and ignition delay time (IDT), typically on the order of 3 ms, of this propellant combination sets it apart from almost all other storable propellants The combination is 1 Research Assistant, Aeronautical & Astronautical Engineering, 500 Allison Rd, West Lafayette, IN 47907, AIAA Student Member 2 Doctoral Candidate, Mechanical Engineering, 500 Allison Rd, West Lafayette, IN 47907, AIAA Student Member 3 Associate Professor, Aeronautical & Astronautical Engineering, 500 Allison Rd, West Lafayette, IN 47907, AIAA Senior Member I Downloaded by PURDUE UNIVERSITY on July 21, 2017 | http://arc.aiaa.org | DOI: 10.2514/6.2015-3867 st AIAA/SAE/ASEE Joint Propulsion Conference July 27-29, 2015, Orlando, FL AIAA 2015-3867 Copyright © 2015 by Purdue University. Published by the American Institute of Aeronautics and Astronautics, Inc, with permission. AIAA Propulsion and Energy Forum American Institute of Aeronautics and Astronautics 2 commonly used for attitude control thrusters which must precisely and rapidly reorient the vehicle. These types of engines seek to minimize the time spent on each engine firing to improve the orientation accuracy of the vehicle. The impressive performance of MMH and NTO explains why this combination has been used for over 50 years. Unfortunately, these propellants are both known to be toxic even at low concentrations ( 1 ppm) in air. MMH is a known carcinogen and NTO will immediately attack the lungs and throat when inhaled. The toxicity of these propellants significantly affects the development and operating costs of any spacecraft that uses them. However, the performance of these propellants has generally outweighed the consequences of handling them for half of a century. Although some less-toxic hypergolic propellants have been suggested, the authors cannot find any history of these propellants being used in spacecraft. In the s, researchers at the China Lake Naval Air Warfare Center – Weapons Division were considering nontoxic hypergolic miscible fuels to provide ignition with rocket grade hydrogen peroxide. These researchers successfully created a mixture of methanol and manganese (II) acetate tetrahydrate, called Block 0, which provided favorable hypergolicity and I sp . However, the development of Block 0 stopped in the early s due to its aging issues (particularly if mixed in a humid air environment) and the requirement for greater than 95 % by weight hydrogen peroxide for low ignition delay and high I sp 2 Recently, researchers at Purdue University have studied less-toxic hypergolic fuels since the mid-1990s. 2 In the past 5 years, Ramachandran et al. extensively tested amine-boranes to determine fuel candidates with low IDT when reacting with white fuming nitric acid (WFNA). 3 Many of the amine boranes tested are solid and Pfeil et al. considered using ethylenediamine bisborane as a hypergolic hybrid fuel additive One of the fuels considered by Ramachandran et al., triethylamine borane (TEAB), is liquid and has an IDT within 1 ms of the IDT of MMH/NTO. 3 Ground testing of hypergolic propellants can be affected by the ambient humidity of each test. MMH and WFNA are known to be hygroscopic, but this property has not yet been determined for TEAB. 5,6 The goal of this research is to measure the change in IDT and ignition intensity of TEAB with WFNA due to varying ambient humidity and oxidizer water concentration levels and to compare the results obtained with TEAB directly to results for MMH. The results of research characterizing TEAB and MMH can be used to further understand the critical reactions that occur in the few milliseconds before ignition. Learning more about the fundamental mechanisms in TEAB and MMH reactions with WFNA can help explain what makes certain propellants good hypergolic candidates. Currently, TEAB seems to be a viable hypergolic fuel and further research into the effects of water and humidity on TEAB is a steppingstone towards finding a less-toxic bipropellant system to replace MMH and NTO. Download 0.9 Mb. Share with your friends:
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