Descent probe or lander power is a key resource for planetary exploration, and is a particular challenge where solar power is difficult to utilize efficiently and alternative power sources are expensive, risky, or complex.
Short duration, battery-powered probes have successfully landed and returned data from the surfaces of cloud-shrouded Venus.
Atmospheric entry probes, such as those for gas giant planets, pose a different problem – the need for high power (up to kilowatts) for short durations. Each of these planetary and mission environments have extremes of temperature, pressure, or other factors, but have dense atmospheres.
Surface pressure on Venus and Titan (and other planets with atmospheres and solid surfaces, and at the bottom of lakes and oceans) is relatively constant, with well-characterized lapse rates and scale heights. Atmospheric density profiles of gas giant planets are known or modeled. Unspooling power systems take advantage of dense atmospheres, utilizing drag forces or buoyant forces to generate electrical power, and in some mission profiles have significant net advantages in mass, cost, power, total energy, and complexity over conventional sources.
Researchers will use drag-using ripcord unspooling power system for descent probes into planets with atmospheres, focusing on an example case of a Saturn Probe.
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Yeah, the Galileo probe was ill-conceived in many ways.
a yoyo like power generation? ok but why not make a Palloon? half balloon and half parachute, or a inflatable parachute. parachute at high speeds and balloon at low speeds to gently descend to the surface. inflate more gas and fly away again.
Like the idea of counter rotating parasails to create electricity. Genius!
I fundamentally object to spending years getting their, and then being content with five minutes operating time. Atmospheric probes should be built to fly in those atmospheres, not fall through them.
It has to be hot to have positive buoyancy in gas giant atmospheres; Hydrogen doesn’t float in hydrogen!
A nuclear battery has huge energy, but not huge power.
Radioisotopes are what you need to give you 50W for 20 years, but doesn’t help with giving you 5 kW for 5 minutes.
They could also put the heat sheilding and related on a long tether, and use that weight for generation.
Though a better option could be a something like a drone. Have props at the top (counter rotating, for example) that take in a large chunk of energy during decent, that allow the probe to charge up and then hover for a few moments and dial in the best landing site. Follow that by turning into long term generators.
Or shoot I don’t know we could… just use better batteries for space exploration.
If only there was some web site that tracked future-y stuff. We could all read articles and complain about missing orders of magnitude and confusion over nameplate capacity.
https://www.nextbigfuture.com/2009/10/liquid-nuclear-battery-that-could-have.html
And in every atmosphere (other than Earth’s) there is no fire hazard for having a balloon filled with Hydrogen and Hydrogen has positive buoyancy.
Turbines are heavy, and require a minimum atmospheric density. Parachutes attached to a winch, as suggested here, would work better.
But maybe a hybrid design is possible, where you use two sets of 2-3 parasails, attached such that each set would rotate in opposite directions.
I looked this up just the other day. Your hydrogen would need to be pretty hot to maintain buoyancy (depending on altitude):
https://en.wikipedia.org/wiki/File:Structure_of_Jovian_atmosphere.png
(On 2nd look, between about -100 and ~300-400 km altitude, it might work. 0 altitude is defined at 1 bar.)
A plane might work better, but it has power-to-weight limitations.
If its going through an atmosphere, why not attach two small wind turbines to create electricity, opposing rotation. That way could also have a basic clutch brake on each. That way to also manuever it, could put the brakes on one to help manuever it. Definately could have worded those last sentences better. Hope you get the just of it.
“Atmospheric entry probes, such as those for gas giant planets, pose a different problem – the need for high power (up to kilowatts) for short durations. ”
There’s no reason to settle for short duration. A nuclear powered probe could loiter in the atmosphere of a gas giant for years, as either a hot hydrogen dirigible using the reactor waste heat, or a sail plane with a small propeller.