Oral Presentation Only

The Adler Planetarium Altitude Control System for Flight Control and Stability of HAB Missions

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Abstract

Background

The Adler Altitude Control System(ACS) is a flight control system for latex HAB missions designed to allowcontrolled venting of helium. In the absence on any mechanism to vent helium atypical latex HAB will rise at a constant rate until it reaches burst altitude.Flight times “at altitude” are well under an hour and involve a constantlychanging altitude. The Adler ACS was developed to maintain extended flight timeat altitude for imaging and to expand the scientific research potential forlatex HAB missions. An unexpected, but extremely important, side benefit hasbeen dramatically improved stability of the HAB platform for imagingexperiments.

 

Mechanicaland Software Design

The Adler ACS is a self-containedventing mechanism inserted into the nozzle of the balloon after filling (Fig.1). It consists of a number of key components including a stopper, an actuator,a Teensy based controller, and a pressure sensor housed in a PVC enclosure.Most mechanical components are custom designed and 3D printed. The unit ispre-programmed with a mission profile describing the desired sequence ofoperations. A typical example might be to retract an actuator at a chosenaltitude opening to allow lift gas to vent, followed by closing the vent whenneutral buoyancy has been detected. After a chosen time based on missionrequirements, the actuator opens the vent to begin descent. With outsidetemperatures reaching below -50C for extended periods during flight, a majorchallenge has been maintaining operational temperatures. By using lithiumthionyl chloride batteries, an outer insulation layer and a nichrome wireheated wrap functional temperature can be maintained.

 

FlightResults

The Adler ACS has been flown onnearly a dozen test flights to date with a variety of flight profiles. Atypical “venting over the top” mission profile opens the vent at 60,000ft andallows helium to escape continuously from then on.

One observed benefit of achieving neutralbuoyancy in our test flights has been to dampen - indeed nearly eliminate -swaying, rotation and instability. An ascending HAB moves with the wind. Ittherefore experiences no forces from horizontal airflow. At typical ascentspeeds (~5m/s), however, it experiences vertical airflow with forces equal tothe buoyancy. Since a latex HAB is far from rigid, it wobbles and deforms underthe influence of the vertical airflow. The power delivered to oscillatory modesis proportional to the third power of the vertical velocity, while theamplitude of motion scales as the 3/2 power. By lowering the ascent/descentspeed we have achieved angular velocities as low as a few×0.1°/sec for extendedperiods of time (Fig. 2). Payloads flown on latex balloons are notoriouslyunstable. Thanks to the stability achieved with this system, we have been ableto perform relatively long exposure nighttime Earth imaging for light pollutionresearch.

Keywords: Altitude Control, flight control, venting

How to Cite:

Tarr, C., Gyuk, G., Garcia, J. & Walczak, K. J., (2019) “The Adler Planetarium Altitude Control System for Flight Control and Stability of HAB Missions”, Academic High Altitude Conference 2019(1). doi: https://doi.org/10.31274/ahac.244