Beyond the obvious military uses for an Entomopter, several NASA Research Centers have noted its unique ability to fly on the planet Mars. Fixed wing aerial Mars rovers would have to fly at over 250 MPH just to stay aloft in the rarefied Mars atmosphere. This makes landing on the rocky surface almost impossible, thereby precluding sample inspection/gathering. Also, the high speed flight means that dwell time on any particular area will be difficult-- a negative feature that is compounded by the fact that turns in the thin atmosphere will require enormous radii.
An Entomopter, on the other hand achieves abnormally high lift with rapidly flapping wings, and therefore allows the fuselage to move slowly in relation to the ground. The Reynolds number for flight on Mars is equivalent to that found at over 100,000 feet here on Earth. Nothing currently flies with any regularity at this altitude. However, the Reynolds number regime for the tiny Entomopter operating in Earth’s atmosphere is equivalent to a larger version (perhaps one meter wing span) operating in the Martian atmosphere. In addition, the gravity on Mars is only 37 percent of that on Earth, so an Entomopter-based Mars Flyer would benefit by proportionately reduced weight, even at its increased size on Mars. An Entomopter-based Mars Flyer holds promise of not only flying slowly over the Martian landscape, but being a multimode vehicle, could land, take samples/recharge/or communicate, and then take off to continue the survey mission. It even has the potential of returning to its launch point for refueling, downloading of data, or transferring of samples (See a streaming video animation of the Entomopter-based aerial Mars Surveyor mission). GTRI has received NASA/NIAC funding to explore the concept of an Entomopter-based Mars Flyer as an upcoming Mars micromission.
A reduced version of the Reciprocating Chemical Muscle was used to obtain empirical data to validate the concept’s ability to develop the power necessary to fly at a reasonable weight. This second generation unit has since been further reduced in sized to produce a muscle capable of reciprocation rates in excess of 60 Hz. This latter unit will be reduced by a factor of 2.5 for the actual terrestrial Entomopter to be constructed. Work toward this goal has been conducted under a grant from the U.S. Air Force (see reduced size versions of the Reciprocating Chemical Muscle second, third, and fourth generations)
Demonstration of a “milli-scaled” Entomopter was the highest rated project for internal funding by the Georgia Tech Research Institute during the 1998 fiscal year. Applications for patents on the various components of Michelson’s research have been submitted with the first having been granted for the overall Entomopter concept on July 4, 2000 and another being granted for the propulsion system September 10, 2002.
Presently, work is progressing to develop the wings for the Mars Entomopter. Stereolithography and Fused Deposition Modeling techniques have allowed Michelson’s design team to create intricate wing structures directly from computer models. Careful attention is being paid to material selection. Resilience, stiffness in opposite planes, chemical compatibility, and ease of bonding are but a few of the points to be considered in choosing wing materials. Wings have been grown in our stereolithography machines as well as ABS wing stiffening structures produced using Fused Deposition Modeling (FDM) methods with, and without interstitial materials. The interstitial material has been placed over the flexible wing structure to demonstrate that micro-channel ribs can be produced to create a wing that can distribute gas to portions of the wing for active flow control to increase lift and produce attitude control moments. Later wing designs are greatly simplified with a single “spar channel” encased in a composite thin wing.
For more information, you may want to read some research papers discussing Entomopter research. Under Phase I of the DARPA Mesomachines for Military Applications program, the Entomopter (or “Mesoscaled Aerial Robot” (MAR)) was defined for a particular misson space. A simulation was constructed to model aerodynamics, thermodynamics, and muscle chemistry to the first order, and was used to predict performance as a function of variables such as weight, wing parameters, and dynamics. A CAD model allowed a full-scale stereolithographic 3D model to be constructed. Methods for in-flight stability and control, navigation, altimetry, and obstacle avoidance were designed and demonstrated in hardware. A rubber band-driven nonresonant flying model was also constructed using wing flapping kinematics of the actual MAR. X-wing flapping flight tests can be viewed here (warning! 5.2 MB movie). Under Georgia Tech IRAD, a second and third generation reciprocating chemical muscle were designed, built, and demonstrated. Although the third generation muscle actuator is still 2X larger than necessary for the operational MAR, its internal porting and components are at about the correct scale, thereby establishing the fact that it can produce the proper power, motion, and frequency to allow MAR flight as predicted by our models.
The full scale terrestrial Entomopter (15 cm wing span) is shown here as a kinematically functional stereolithographic model incorporating major flight structures, reciprocating chemical muscle, fuel storage, and obstacle avoidance projection ports (below). The inset at the above link is an elastically-powered model in flight.
The kinematics of the X-wing flapping Entomopter were first studied in a mechanical analog system. (Here is “the real thing”).
to insect-like aerial robotic flight:
Robert C. Michelson Principal Research Engineer, Emeritus Georgia Tech Research Institute Aerospace, Transportation & Advanced Systems Laboratory (ATAS-CCRF) 7220 Richardson Road Smyrna, Georgia 30080 U.S.A. firstname.lastname@example.org