The reciprocating chemical muscle (RCM) is a mechanism that takes advantage of the superior
energy density of
chemical reactions
A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking ...
. It is a regenerative device that converts chemical energy into motion through a direct noncombustive chemical reaction.
Function
RCM is capable of generating
autonomic wing beating from a chemical energy source. It can also be used to provide a small amount of electricity to the onboard control systems. It further helps in differential lift enhancement on the wings to achieve roll, pitch, and hence, steered flight. The RCM technique is particularly useful in the manufacturing of insect-like
micro air vehicle
A micro air vehicle (MAV), or micro aerial vehicle, is a class of miniature UAVs that has a size restriction and may be autonomous. Modern craft can be as small as 5 centimeters. Development is driven by commercial, research, government, and mil ...
s. The first generation of RCMs was large and had a reciprocating frequency around 10 Hz. The later generations
[http://angel-strike.com/entomopter/RCM-Generations.jpg ] developed were very much smaller and lighter. Also, the reciprocating frequency of this generation RCM was as high as 60 Hz. The reciprocating chemical muscle was invented by Prof.
Robert C. Michelson of the
Georgia Tech Research Institute and implemented up through its fourth generation by Nino Amarena of ETS Laboratories.
Benefits
Particular benefits of the RCM are:
*It requires no ignition source (thereby allowing it to work in explosive atmospheres).
*It is independent of external oxidant (thereby allowing it to operate under water or in oxygen-free environments such as the lower atmosphere of the planet
Mars
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...
).
*It
thermoelectrically generates electrical energy from its own exothermic metabolism.
*It converts chemical potential energy directly into
kinetic energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acc ...
with greater
energy density than batteries.
[Michelson, R.C., ''Novel Approaches to Miniature Flight Platforms,'' Proceedings of the Institute of Mechanical Engineers, Vol. 218 Part G: Journal of Aerospace Engineering, Special Issue Paper 2004, pp. 363–373 https://journals.sagepub.com/doi/10.1243/0954410042794911]
Mechanism
The reciprocating chemical muscle uses various
monopropellant
Monopropellants are propellants consisting of chemicals that release energy through exothermic chemical decomposition. The molecular bond energy of the monopropellant is released usually through use of a catalyst. This can be contrasted with bipro ...
s in the presence of specific
catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
s to create gas from a liquid without
combustion
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combus ...
.
[Colozza, A., Michelson, R.C., ''et al.'', ''Planetary Exploration Using Biomimetics – An Entomopter for Flight on Mars,']
Phase II Final Report (see chapter on fuels)
NASA Institute for Advanced Concepts Project NAS5-98051, October 2002.
abstract
/ref> This gas is used to drive reciprocating opposing cylinders (in the fourth-generation device) to produce sufficient motion (throw) with sufficient force and frequency
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
to allow flapping-wing flight. As of 2004, the RCM had been demonstrated in the Georgia Tech Research Institute laboratory to achieve sufficient throw, force, and frequency for operation of a 50-gram entomopter while using high concentration (> 90%) hydrogen peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%â ...
in the presence of a proprietary catalyst developed by ETS Laboratories.[Michelson, R.C., Naqvi, M.A., ''Extraterrestrial Flight (Entomopter-based Mars Surveyor),'' von Karman Institute for Fluid Dynamics RTO/AVT Lecture Series on Low Reynolds Number Aerodynamics on Aircraft Including Applications in Emerging UAV Technology, Brussels Belgium, 24–28 November 2003]
Specific uses
The reciprocating chemical muscle was developed as a drive mechanism for the flapping wings of the entomopter. The RCM reuses energy many times before releasing it into its surroundings.[Michelson, R.C., 'Neurotechnology for Biomimetic Robots,'' , The MIT Press, September 2002, pp. 481 – 509, (chapter author)] First, it converts mainly heat energy into flapping-wing motion in the entomopter. Then, heat is scavenged for thermoelectric
The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when ...
generation in support of ancillary systems. Waste gas from the chemical decomposition of the fuel is then used to create a frequency modulated continuous wave
Continuous-wave radar (CW radar) is a type of radar system where a known stable frequency continuous wave radio energy is transmitted and then received from any reflecting objects. Individual objects can be detected using the Doppler effect, whi ...
acoustic ranging signal that is Doppler insensitive (used for obstacle avoidance). Waste gas is then passed through an ejector to entrain external atmospheric gases to increase mass flow and decrease waste gas temperature so that lower-temperature components can be used downstream. Some waste gas is diverted into gas bearings for rotational and linear moving components. Finally, remaining waste gas is vectored into the wings where it is used for circulation-controlled lift augmentation ( Coanda effect). Any remaining gas can be used for vectored thrust
Thrust vectoring, also known as thrust vector control (TVC), is the ability of an aircraft, rocket, or other vehicle to manipulate the direction of the thrust from its engine(s) or motor(s) to control the attitude or angular velocity of the v ...
, but if the gas budgets are correctly designed, there should be no extra gas beyond the circulation control points. The features of the RCM are tailored to the entomopter to conserve energy.
References
{{reflist
External links
Robert C. Michelson: Entomopter Project
* "Reciprocating Chemical Muscle (RCM) and Method for Using Same", U.S. Patent No. 6,446,909, September 10, 2002
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