Effect of heat from future Titan landers Options

[lilmac]

We know that heat from the Huygens lander vaporized methane, suggesting the craft had landed in a damp area. Might radiant heat pose problems for observations and measurements from future landers? Could we have a scenario where for instance cameras are affected by "steaming" methane? Unlikely? Far-fetched?

[Explorer1]

Depends on where the power source is, how hot it gets, etc. Legs would work, like on Phoenix, but there the exhaust turned out to have some serendipitous effects (a free excavation, no digging necessary).

[rlorenz]

We know that heat from the Huygens lander vaporized methane, suggesting the craft had landed in a damp area. Might radiant heat pose problems for observations and measurements from future landers? Could we have a scenario where for instance cameras are affected by "steaming" methane? Unlikely? Far-fetched?

Note that methane was not substantially evaporated by the Huygens probe body itself, but by the (deliberately) heated GCMS inlet that was embedded in the ground. However, the highest power density dumped into the surface was the DISR lamp, which put out about 20W onto a small patch of ground. There was no steaming (or even shimmering) detected, although some methane may have condensed on the camera baffle - one of the hundreds of images post-impact shows a feature that can be modeled as a 4mm methane drop about 11cm in front of the lens. Or it could have been a big, wierd, cosmic ray hit.

Rest assured that designers of future missions are alert to such effects. Note that Titan is nothing special in this regard - all
landers introduce perturbations to their environment (Phoenix, Pathfinder and Viking all report winds/temperatures being perturbed from some directions). These effects can be studied and mitigated using modern tools such as Computational Fluid Dynamics.

[Phil Stooke]

This came up with Viking in the early days of site selection. Carl Sagan asked the Site Selection team if the spacecraft would heat the surface, but an analysis (possibly by Hugh Kiefer, but I don't have my notes with me) showed it would cool the surface more by shadowing than heat it by thermal radiation.

Phil

[Tom Dahl]

Regarding the Viking landers, an additional serious concern was a short-term one: within the first hour or so after landing, would the three hydrazine monopropellant Terminal Descent Engines radiate enough heat to harm the spacecraft, or alter (e.g., sterilize) the local surface? The prominent gold-plated aluminum shields which wrap around the sides of the TDEs were added to reduce the transfer of thermal energy, along with a layer of min-K insulation bonded to the exterior of the thrust chamber. The rhodium plating on the nozzles and bottom of the aft dome, along with their very fine surface finish, also reduce radiant energy.

[lilmac]

Note that methane was not substantially evaporated by the Huygens probe body itself, but by the (deliberately) heated GCMS inlet that was embedded in the ground. However, the highest power density dumped into the surface was the DISR lamp, which put out about 20W onto a small patch of ground. There was no steaming (or even shimmering) detected, although some methane may have condensed on the camera baffle - one of the hundreds of images post-impact shows a feature that can be modeled as a 4mm methane drop about 11cm in front of the lens. Or it could have been a big, wierd, cosmic ray hit.

Rest assured that designers of future missions are alert to such effects. Note that Titan is nothing special in this regard - all
landers introduce perturbations to their environment (Phoenix, Pathfinder and Viking all report winds/temperatures being perturbed from some directions). These effects can be studied and mitigated using modern tools such as Computational Fluid Dynamics.

Thank you very much. This and others are very informative. I really hope Titan MARE gets approved. The excitement on Europa is justified but we are not ready technologically speaking to explore the subsurface ocean in situ. Witness the difficulties we have in reaching Lake Vostok. Titan on the other hand, can be satisfactorily explored - today.

[Greenish]

I have wondered for some time about this effect with regard to ice in shadowed craters on the moon. If the only reason that ice has accrued over very long timescales is because it is shadowed and therefore at very low temperature, would a rover that attempted to characterize it or retrieve it cause it to sublime due to radiant heat?

[Phil Stooke]

Good point, but the lunar ice rover would be very well insulated to keep itself as warm as possible, which will help this. Also we expect the ice to be mixed into regolith, not very much of it right at the surface.

Phil

[Greenish]

Thanks. Figured it had been considered, just didn't know if it was a deal-breaker.