NASA engineer Michael Paul presented a novel idea where existing technology could be used to make longer-duration missions to Venus in a seminar called “An Air-Breathing Metal-Combustion Power Plant for Venus in situ Exploration”.
To recap the history of Venus exploration, very few probes have ever been able to explore its atmosphere or surface for long.
Not surprising, considering that the atmospheric pressure on Venus is 92 times what it is here on Earth at sea level.
Not to mention the fact that Venus is also the hottest planet in the Solar System – with average surface temperatures of 737 K (462 °C; 863.6 °F).
Hence why those few probes that actually explored the atmosphere and surface in detail – like the Soviet-era Venera probes and landers and NASA’s Pioneer Venus multiprobe – were only able to return data for a matter of hours.
All other missions to Venus have either taken the form of orbiters or consisted of spacecraft conducting flybys while en route to other destinations.
Having worked in the fields of space exploration and aerospace engineering for 20 years, Michael Paul is well-versed in the challenges of mounting missions to other planets.
The flagship mission to Titan was the subject of Paul’s work since joining Penn Sate’s Applied Research Laboratory in 2009.
During his time there, he became a NASA Innovative Advanced Concepts Program (NIAC) Fellow for his co-creation of the Titan Submarine.
For this mission, which will explore the methane lakes of Titan, Paul helped to develop underwater power systems that would provide energy for planetary landers that can’t see the Sun.
Having returned to JHUAPL, where he is now the Space Mission Formulation Lead, Paul continues to work on in-situ concepts that could enable missions to locations in the Solar System that present a challenge.
In-situ exploration, where local resources are relied upon for various purposes, presents numerous advantages over more traditional concepts, not the least of which is cost-effectiveness.
Consider mission that rely on Multi-Mission Radioisotope Thermoelectric Generators (MMRTG) – where radioactive elements like Plutonium-238 are used to generate electricity.
Whereas this type of power system – which was used by the Viking 1 and 2 landers (sent to Mars in 1979) and the more recent Curiosity rover – provides unparalleled energy density, the cost of such missions is prohibitive.
What’s more, in-situ missions could also function in places where conventional solar cells would not work. These include not only locations in the outer Solar System (i.e. Europa, Titan and Enceladus) but also places closer to home.
The South Pole-Aitken Basin, for example, is a permanently shadowed location on the Moon that NASA and other space agencies are interesting in exploring (and maybe colonizing) due to the abundance of water ice there.
But there’s also the surface Venus, where sunlight is in short supply because of the planet’s dense atmosphere. As Paul explained in the course of the seminar:
“What can you do with other power systems in places where the Sun just doesn’t shine?
Okay, so you want to get to the surface of Venus and last more than a couple of hours. And I think that in the last 10 or 15 years, all the missions that [were proposed] to the surface of Venus pretty much had a two-hour timeline.
And those were all proposed, none of those missions were actually flown. And that’s in line with the 2 hours that the Russian landers survived when they got there, to the surface of Venus.”
The solution to this problem, as Paul sees it, is to employ a Stored-Chemical Energy and Power System (SCEPS), also known as a Sterling engine. This proven technology relies on stored chemical energy to generate electricity, and is typically used in underwater systems.
But repurposed for Venus, it could provide a lander mission with a considerable amount of time (compared to previous Venus missions) with which to conduct surface studies.
For the power system Paul and his colleagues are envisioning, the Sterling engine would take solid-metal lithium (or possibly solid iodine), and then liquefy it with a pyrotechnic charge.
This resulting liquid would then be fed into another chamber where it would combined with an oxidant. This would produce heat and combustion, which would then be used to boil water, spin turbines, and generate electricity.
Such a system is typically closed and produces no exhaust, which makes it very useful for underwater systems that cannot compromise their buoyancy. On Venus, such a system would allow for electrical production without short-lived batteries, an expensive nuclear fuel cell, and could function in a low solar-energy environment.
An added benefit for such a craft operating on Venus is that the oxidizer would be provided locally, thus removing the need for a heavy component.
By simply letting in outside CO2 – which Venus’ atmosphere has in abundance – and combining with the system’s liquefied lithium (or iodine), the SCEPS system could provide sustained energy for a period of days.
Paul and his colleagues were able to test their concept, and found that it was capable of producing sustained heat that was both controllable and tunable.
Further help came from the Glenn Research Center’s COMPASS lab, were engineers from multiple disciplines performs integrated vehicle systems analyses.
From all of this, a mission concept known as the Advanced Lithium Venus Explorer (ALIVE) was developed.
Paul and his team finally envision a mission where a lander would reach the surface of Venus and study it for 5 to 10 days.
All told, that’s an operational window of between 120 and 240 hours – in other words, 60 to 120 times as long as previous missions.
From a purely technological standpoint, this not a new idea. But in terms of space exploration, it has never been done before. Granted, there are still many tests which would need to be conducted before any a mission to Venus can be planned.
Space exploration is always a challenge. Whenever ideas come along that make it possible to peak into more environments, and on a budget to boot, it is time to start researching and developing them!
News source: Universe Today. The content is edited for length and style purposes.
Figure legend: This Knowridge.com image is credited to NASA.