Effect of heat from future Titan landers |
Effect of heat from future Titan landers |
Jun 26 2012, 02:36 AM
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#1
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Newbie Group: Members Posts: 6 Joined: 27-January 12 Member No.: 6325 |
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?
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Jun 26 2012, 06:50 AM
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#2
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Senior Member Group: Members Posts: 2082 Joined: 13-February 10 From: Ontario Member No.: 5221 |
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).
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Jun 26 2012, 08:39 PM
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#3
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Member Group: Members Posts: 610 Joined: 23-February 07 From: Occasionally in Columbia, MD Member No.: 1764 |
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. |
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Jun 27 2012, 12:01 AM
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#4
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Solar System Cartographer Group: Members Posts: 10151 Joined: 5-April 05 From: Canada Member No.: 227 |
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 -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Jun 27 2012, 12:23 PM
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#5
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Member Group: Members Posts: 101 Joined: 3-May 12 From: Massachusetts, USA Member No.: 6392 |
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.
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Jun 28 2012, 07:46 PM
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#6
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Newbie Group: Members Posts: 6 Joined: 27-January 12 Member No.: 6325 |
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. |
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Jul 1 2012, 05:23 PM
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#7
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Member Group: Members Posts: 219 Joined: 14-November 11 From: Washington, DC Member No.: 6237 |
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?
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Jul 1 2012, 07:19 PM
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#8
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Solar System Cartographer Group: Members Posts: 10151 Joined: 5-April 05 From: Canada Member No.: 227 |
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 -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Jul 2 2012, 01:36 AM
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#9
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Member Group: Members Posts: 219 Joined: 14-November 11 From: Washington, DC Member No.: 6237 |
Thanks. Figured it had been considered, just didn't know if it was a deal-breaker.
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