Desert Tests of Altitude Control and Sample Collection System

Artist Concept of Montgolfiere
Ground Sample Collection System

Solar Montgolfiere Stratospheric and Altitude Control Testing

Solar-heated hot air balloons, or solar Montgolfieres, can provide buoyancy for payloads at any planet near the sun (<10 AU). Tests on Earth have, in fact, confirmed this simple principle. With a recent novel, JPL-developed, radio-controlled winch, the balloon volume, and thus buoyancy, can now be varied to provide precise altitude changes and can actually provide controlled landings at Mars and altitude controllability at Venus, Jupiter, and Saturn. Solar-heated hot air balloons are the only viable means to fly balloons at the primarily hydrogen planets of Jupiter and Saturn. Where others have failed, however, JPL has recently found a simple winching mechanism that allows the top of the balloon to be pulled down, thus reducing the volume and buoyancy of the balloon. To date, this buoyancy-varying technique has only been confirmed at low altitudes, although it may eventually be confirmed for low-pressure (high altitude) deployment and operation, which is the anticipated deployment condition for Mars, Jupiter, and Saturn. The novel buoyancy control mechanism would allow balloons to make multiple controlled ground-sampling and testing runs over long distances on Mars, especially in the constant sunlight of a long polar summer. It could also allow very long duration flights of balloons on Jupiter and Saturn that can fly just above the lower water/ammonia clouds and survive the nights (~5 hours) by climbing very high before sunset.

A series of hundreds of low altitude deployments of non-altitude-controlled Montgolfieres occurred as part of the JPL balloon test program during 1997-1998. In these tests, packed Montgolfieres were dropped from tall buildings at JPL, and from commercial hot air balloons. All testing showed that as long as an opening device was present in the bottom of the Montgolfiere, then the balloon would fill and heat very quickly.

These tests were followed by a series of high altitude tests simulating entry into the Mars atmosphere. A series of tests has recently been conducted in which stowed solar Montgolfiere balloons have been carried into the Earth's stratosphere by a helium tow balloon. The Montgolfiere balloons are typically deployed at 32-36 km altitude, where the Earth's temperature and pressure are similar to Mars (210 K and 0.006 bar). Of the flights thus far conducted, four have deployed successfully, showing that this type of technology is indeed feasible.