Future Venus Missions |
Future Venus Missions |
Jul 1 2005, 01:30 AM
Post
#1
|
|
Solar System Cartographer Group: Members Posts: 10256 Joined: 5-April 05 From: Canada Member No.: 227 |
Oh well, might as well start that new topic since it's already well advanced in the Juno area...
My perspective on landers is as follows. All the landers we've had so far were dropped blind onto an essentially unknown surface. Any future landers can be targeted for specific terrains. It really is not true that we have had representative landings. Even a descent image or two, a panoramic photo plus a bit of surface composition, from a simple Venera-class lander just updated a bit, would be useful if we could put several down at well chosen targets. My choices would be: Examples of the main plains units (smooth, fractured, ridged) tesserae high elevation radar-bright tesserae large fresh lava flow unit ('fluctus') crater dark parabola crater ejecta outflow unit dunes area. And I have always assumed, rightly or wrongly, that it would be relatively easy to put these down, so they ought to be fairly inexpensive as planetary landers go. 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 PDF: 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) |
|
|
Guest_BruceMoomaw_* |
Jul 1 2005, 11:28 PM
Post
#2
|
Guests |
The main justification for simplifying a Venus lander is that it can enable you to launch more than one at one time. Larry Esposito's "SAGE" concept -- which, from what little I know about it, apparently DID have both an airlock and a GCMS atmospheric analyzer -- neverthless consisted of two or three landers on one mission.
|
|
|
Jul 7 2005, 02:39 PM
Post
#3
|
|
Member Group: Members Posts: 593 Joined: 20-April 05 Member No.: 279 |
Given that the surface is so hot and so highly pressured, why not take a leaf from the early explorers of the ocean bottoms? Dredge for rocks!
Picture a balloon flying in Venusian atmosphere at about the 32km level. This height is good since it's below the bulk of the cloud cover, giving you the ability to view the surface. Pressure is around 8bar and the temperature is around 200C. Not really a problem for well-designed electronics & balloon materials. Water doesn't automatically boil at this pressure/temp, so may be useful for radiators. A thin titanium wire, with a basic end effector, could be winched down from a balloon at this height to pick up suitable rocks for analysis back within the balloon. A wire some 1.32 mm across, tapering to around 1mm at the bottom, would in total mass about 160kg, and enable a load of about 20kg to be lifted, assuming some 5kg mass for a grabber/hardened camera, etc. 100kg of lift in a CO2 atmosphere could be provided with just under 8 cubic metres of H2 in the balloon, so the size of the bag could be really quite trivial. Andy G |
|
|
Jul 7 2005, 02:54 PM
Post
#4
|
|
Senior Member Group: Members Posts: 2488 Joined: 17-April 05 From: Glasgow, Scotland, UK Member No.: 239 |
As there are some fairly well-described outline designs for RTG-powered refrigerated landers, I find myself wondering whether the waste heat from the refrigeration system could be used to produce lift in a hot-air balloon. An almost mechanically inert (in terms of externals - obviously, there's pumps and whatnots beavering away inside!) lander could drift around the landscape, rising from time to time then falling once more. Think of a Galilean Thermomoter, and the way the glass spheres bob up and down...
You'd get: Multiple ground-truth sites Aerial imaging Meteorology And probably a few other goodies, too! -------------------- Remember: Time Flies like the wind - but Fruit Flies like bananas!
|
|
|
Jul 7 2005, 08:18 PM
Post
#5
|
|
Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
QUOTE (Bob Shaw @ Jul 7 2005, 07:54 AM) As there are some fairly well-described outline designs for RTG-powered refrigerated landers, I find myself wondering whether the waste heat from the refrigeration system could be used to produce lift in a hot-air balloon. An almost mechanically inert (in terms of externals - obviously, there's pumps and whatnots beavering away inside!) lander could drift around the landscape, rising from time to time then falling once more. Think of a Galilean Thermomoter, and the way the glass spheres bob up and down... You'd get: Multiple ground-truth sites Aerial imaging Meteorology And probably a few other goodies, too! It'd be great if it worked, but of course, the refrigeration scheme itself involves a lot of mass per payload mass. Venus permits a lot of buoyancy, potentially, especially if helium filled the balloon, but that margin could be eaten up with a nuclear-powered refrigerator + thermal insulation + ??? Also, heated CO2 would not give you much buoyancy compared to helium unless you really heated the hell out of it. Venus's high ambient temperature really works against that. To halve the density of CO2, you'd have to double the temperature, up to roughly 1000K! I'm no material scientist, but I guess you're talking about fewer and fewer possible balloon materials that will hold up as a strong, thin film when boosted to white heat! I think compressing and uncompressing helium (at thermal equilibrium with the outside) would provide a *lot* more lift with less mass. Although, I understand and admire you're looking for synergy between a design side-effect and a possible desirable feature. The synergy you get in design with Venus balloons is that the higher a balloon resides, the cooler the ambient temperature that must be withstood. If thermal inertia (passive!) can keep the system alive throughout a single exploratory drop, then we might have systems that can only tolerate the Venusian surface environment temporarily, but long enough for an arbitrary number of descents. The Veneras operated in this fashion. A balloon carrying a heat sink could reach thermal equilibrium at 40-100 C. Then the question is: How much time would be required in a surface stay to do useful science? For imagery, very little. To grab a sample, very little. It is possible, in times of favorable geometry, to work a single telemetry/command feedback loop with Earth-based controllers in just a few minutes. (Transmit an image, ask which rock/soil unit should be grabbed, and receive that command -- the AI for that is beyond MER, but not beyond reason.) If a ~45-minute surface stay is well within safe margins for thermal constraints, then that's not a bad MO. If descents could be managed at roughly the rate of one per day, then a lot of surface exploration could take place in a primary mission of two or three weeks. The whole scheme then could be to identify a swath across one line of latitude of Venus that contains several worthwhile terrain units that are, moreover, going to be in local daylight with a line-of-sight to Earth during a desired primary mission. The craft would control its horizontal motion by ascending into local winds, thereby deriving the horizontal motion. The heat sink would get well below top operating temperature, and then the craft would perform a dive to its target. It would take descent images and a single surface panorama, beam them to Earth, and autonomously perform surface science while awaiting a command from Earth identifying which surface patch to sample by arm. After about 20 minutes, the human-made decision would reach the craft, an arm would make a grab for the target, and then the craft would ascend again, and spend its time analyzing the sample up in the cool heights above. An exploration of terrains in the vicinity of 150 E, moving along the equator or 10 S -- could be a heck of a mission, with lots of geological and "remote" sensing of many terrains. Of course, if a pair of these things could be afforded, working at different latitudes but identical longitudes in the same time frame, then a very thorough exploration would result. |
|
|
Lo-Fi Version | Time is now: 31st October 2024 - 11:21 PM |
RULES AND GUIDELINES Please read the Forum Rules and Guidelines before posting. IMAGE COPYRIGHT |
OPINIONS AND MODERATION Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators. |
SUPPORT THE FORUM Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member. |