Hello again,

With the Martian airplane concept becoming sort of abandoned these days, I just wonder if a Martian CHOPPER was ever considered. With the capability of MRO I guess we do not need airborn instruments dedicated to imaging there. But: what about chemical measurements and "sniffing" for volatiles? Imagine something that could land at one spot found to be interesting on MRO photos and then take off and go sniffing for methane somewhere else? What do you think? Does it make any sense to you?

Regards,

Karol P.

Poland

I've changed the topic of the thread - you wrote it as if such a vehicle were already planned, not as if you were posing a question.

As for choppers on Mars.....I find it very hard to imagine them working....you've going to need such large blades, such high rotation, and such a small payload to get it off the ground. A balloon would make MUCH MUCH more sense to achieve the same thing and be much simpler to boot.

Doug

Helicopters on Titan, that's the thing. You use an RTG to generate electricity, or even a simple nuclear heater to power a Stirling engine to do the same, then you expend it in more-or-less one go, and autorotate to a landing. You wait a few days, then take off again. On Mars, Zubrin's in-situ fuelled baby aeroplane makes a lot of sense, too (perhaps more so on Titan - just bring an oxygen supply down to the surface with you and burn the air, or crack it out of water ice!). Or perhaps on Titan you could try an aerodyne, a semi-buoyant vehicle with an aerodynamic shape which flies by generating lift, then drifts down. Or...

Bob Shaw

Thank you for correcting me. I also thought the design would have to be modified to suit the thin Martian atmosphere. But on the other hand it is probably somewhat compensated by less gravity. I would imagine a small but well equipped payloayd attached to a fast spinning rotator. A balloon might get punctured at some point. But a RTG-powered chopper could make a significant number of lift-offs and landings followed by chemical measurements saving a lot of money on tons of landers to be placed in different areas... It is kind of neat to have the MERs able to MOVE But imagine something that could actually lift itself above the surface and FLY to sniff rocks tens of kilometers apart...

Variations on the hot air balloon theme make a lot more sense For Titan as you can use the heat from the RTG directly instead of losing about 90 percent of it in a highly inefficient electric generator. However I imagine any balloon would have to be quite large in the case of Mars due to the thin atmosphere, and a hot-air one would presumably require several times the volume of a hydrogen-filled one to provide the same lift.

Off the wall query: Would it be possible (on any planet) to use focussed sunlight plus greenhouse effect to power a hot air balloon? I am picturing a double skin balloon black on the inside with the outer membrane opaque to long wavelength IR, and a large but light parabolic reflector suspended beneath.

Oh - I've seen pdf's and ppt's showing Mars balloons that heat up in the morning - expand, take off - drift for the day then settle down again as it cools in the evening and have an analogy to 'drag chains' to park up overnight to do overnight obs of some sort.

Doug

Very interesting. How do people rate these ideas? Should they be taken seriously? I can't see any obvious reason why not. Using in-situ resources for both baloon-filling gas and power seems very appealing, almost too good to be true - but maybe it's just too good not to try?

Actually, balloons were not only considered. They were built by the French for the Russians but the mission ended up exploring the bottom of Earth's ocean. It it were not so, and if Mars Observer didn't fail, we would have remembered it as the first orbiter to relay data from a balloon dragging a "snake" on the surface:

"Mars Observer was also to support the acquisition of data from the Russian Mars 1994 mission through the use of the joint French-Russian-American Mars BALLOON Relay instrument."

http://nssdc.gsfc.nasa.gov/database/Master...og?sc=1992-063A

And:

"The design and utilization plans for the Mars Balloon guiderope are described with attention given to environmental and mission constraints. The guiderope is intended to enable the balloon to fly close to the Martian surface to sample the surface and near-surface atmosphere. The 'Snake' concept is described for this application which comprises overlapping cones that provide a smooth dragging surface as well as structural flexibility. A 'tail' segment of small diameter is attached to the Snake that stabilizes the guiderope with titanium shells and also serves as half of the required radar dipole antenna. A specific design is set forth for the Snake and Tail elements that provides dust-tolerant effectiveness without lubricant for the extreme conditions of the Martian surface. The resulting guiderope for the Mars 96 Balloon Mission is expected to render the exploratory mission effective."

http://adsabs.harvard.edu/abs/1992wadc.iafcY....L

The Mars 96 mission was supposed to have a balloon on board that Doug speaks of. According to this site http://barsoom.msss.com/mars_images/mars_r.../mer_index.html the balloon never made it to the payload. It wouldn't have made it to Mars anyway...


http://www.omnitron.net/radar/0mars.htm
http://www.springerlink.com/content/h60754884137p8k1/

Just yesterday I happened to see a photo of a flying machine for Mars. It was designed by Pioneer Astronomics and is called a "vertical takeoff flying machine".

http://www.geotimes.org/july06/feature_SpaceJetting.html





Click to view attachment

Just to be pedantic, it's often stated that Mars 96 ended up in the Pacific, but it actually came down in Bolivia or surrounding territories; several people at ESO observed it descend.

10 years may have blurred the details, but as I recall... The confusion over its final resting place is probably caused by the fact that NORAD announced it was tracking the spacecraft after it failed to leave Earth orbit, and, if I recall correctly, the US offered help to Australia if the spacecraft with its plutonium power supplies landed on their territory. They then announced that it had re-entered "safely" over the Pacific. It was later realized that NORAD had been tracking the final stage, and that Mars-96 itself had already detached and had re-entered the Earth atmosphere over the Andes. No-one offered Bolivia help with the clear-up though, and as far as I know, the debris has not been located.

It was a huge loss... the most massive interplanetary spacecraft ever launched; even exceeding Cassini's mass.

Really? I thought its propulsion system had to be used for part of the earth escape burn. It so, any mass allocated to this, is not part of the "spacecraft" but part of the LV and therefore it wasn't "big"

It was a great loss at the time, but putting it in perspective we can now fly far more advanced missions (and several of them) with a considerably lower mass budget. The lucky thing is agency-level interest in Mars was never allowed to wane (at least in NA) despite the meteoric ending for the mission. It may have given NASA and JPL more bragging rights in the end.

It's fascinating to speculate, but helicopters are completely at the mercy of air density. They really only are marginally flyable on Earth as a narrow rotating airfoil is extremely wasteful of lift. Energy inputs are hugely out of proportion to the lift provided. As for refilling CO2 canisters with each hop, when there is a CO2 pipeline on Mars that could be a reality. Or perhaps it is more like gassing up a bottle of party soda? I'd agree that anything other than balloons or ultra ultralight fixed airfoil craft is in the realm of the most remote and fanciful speculation for commuting about Mars.

In addition to carbon dioxide, I suspect that device relies heavily on smoke and mirrors.




Edit:

More on the "gashopper" from the Mars Society:

http://www.marssociety.org/news/2005/0730.asp

I think so... according to the IKI web pages, Launch mass was 6700 kg, of which 3000 kg fuel, and 550 kg instrumentation. NSSDC states that on-orbit dry mass was 3159 kg. Apparently the propulsion unit was to be jettisoned a few weeks after arrival at Mars; I don't know how massive this was - maybe this would tip the scales in Cassini's favour? (but then again Cassini has a not-detachable propulsion unit essential for Saturn orbital insertion)

Cassini: Orbiter alone: 2150 kg, Huygens: 350 kg, Fuel: 3132 kg. Total with launch adaptor: 5600 kg. The Wikipedia entry on Cassini (usual caveats re. Wikipedia apply!) states that the Phobos spacecraft were more massive too.

I'm happy to be corrected on this.

Top Trumps anyone?

Compared to fixed-wing and lighter-than-air craft, the big advantage to helicopters on earth is the maneuverability. Why would this be an advantage on Mars? Especially considering the extra overhead needed for a helicopter?

A prototype of a Mars autogyro (a sort of helicopter) was under study at ESA during the late nineties

I can't see any reason for doing this rather than a balloon but it seems that you can make a stab at building one in a simulator yourself.

A delayed thank you to doug, karolp and remcook for the info on the Mars 96 trailing balloon design. I hope something like this is tried again.

Theres not only one but several obstacles thaty I can see.
Even though there are some advantages to one helicopter such as the ability to land on a selected spot. It does not neccesarily apply for exploration on Mars.

Since the rotor would have very long blades they would hang down to quite a dergee.
(Ever seen the rotorblades of a really large helicopter? They droop downwards to quite a degree, for a martian helicopter that length need to be something like ten times longer.)

It will require a very smooth area where the heli lands and takes off, else any tip could hit a rock and there would be one premature end of mission. Again the very long rotorblades.

As for plain engineering, there are several problems. With very long blades the tips would be moving at one very high speed. Turning can be very slow caused a lot of intertia in the entire rotor. Not to mention the stress at the center and the drive mechanism.

Helicopters dont fly on higher elevations here on Earth, but aircrafts do. So some kind of aircraft are a better choice for several reasons. Flying winged craft in extremely thin air are a known technology and not something where it would be neccesary to invent the wheel again.

Yet another major disadvantage of UMSF helicopters in general is the fact that the rotary mechanism & its associated subsystems are extremely complex, obviously moving parts, and therefore reliability nightmares. For example, the Sikorsky S-70 requires a rotor head inspection every 10 flight hours, and there are often findings that must be corrected.

Bottom line is that even if a helo designed for Martian conditions was practical using current technology, I doubt that it would survive very long. (I'll forgo discussing the detrimental effects of Martian dust, but trust me: it'd be ugly. Just one example: Erosion of the leading edges of the rotor blades would begin immediately & thereby progressively reduce lift). The first choppers on Mars should probably be built by the Meridiani Colony branch of Sikorsky Interplanetary LLC circa 2400 AD so that they can receive the proper maintenance...

Airplanes fly by the laws of aerodynamics.
Helicopters fly by brute engineering force.
:-)

Or subcontract to MiL - theirs didn't need any maintenance at all, and ran on grain alcohol. Hic!


Bob Shaw

Long rotor blades can't move very fast since the blade tips will reach supersonic speed for part of the rotation. It is (barely) practicable to use supersonic propellers, but not supersonic rotors. The stability and control problems would be horrendous, not to mention the strain on the blades.

IMHO a martian helicopter or gyroplane is quite impracticable while a fixed-wing aircraft might just be feasible. It would have to fly quite fast though in such a thin atmosphere. The best solution would probably be a balloon or perhaps some kind of a hybrid which derives part of the lift aerodynamically when moving. Airships regularly did (and do) this.

tty

There is another variation on that I actually heard from a helo pilot:

"Helicopters can't really fly, they are simply so ugly that they are naturally repelled by the Earth"

tty

There's a tape out there by an ex pilot who did an after dinner speach....it's infamous and amazing....one section is something like this

"Helecopters are different - you put on phenomanal ammounts of power and it defies all known law - and lift off. It should of course screw itself into the ground. Once you've got it up in the air you grab hold of the stick and go crazy with the thing - then you hold it in one place and watch what the helecopter does....because if you want it to do that again....that's where you put the stick"



Doug

...yep. Back in the day when I worked avionics on HH-60s (including flight controls) it really seemed like no two choppers flew alike. I must have changed a dozen trim actuators (and many, many more stability augmentation computers) for no other reason than that the beast "didn't feel right"...

Point being that I really can't imagine UM helos on Mars or anywhere else. Not to knock those who propose this idea, though; it's a neat concept, and their capabilities would be tremendous with respect to exploratory applications. The sad fact is that copters require a lot of TLC to fly at all, so their survivability as remote platforms is quite limited indeed.

""Helicopters can't really fly, they are simply so ugly that they are naturally repelled by the Earth"

I LOVE it!

Gyros, though, make a certain amount of sense, especially those which can jump-start into the air. They offer most of the advantages of a helicopter but are much simpler in execution. They are also seriously silly vehicles - I once saw a friend take off *across* a runway, just for fun!


Bob Shaw

Gyroplanes have very limited altitude capability (the world record is only about 8,000 meters I think). I can't imagine one getting airborne on Mars, and certainly not across a runway!

tty

Yes, Mars *is* pretty much a worst-case scenario for whirling things - but Titan, now there's the place: high atmospheric pressure, low gravity, light winds...


Bob Shaw

Titan would of course be far more rotary-friendly than Mars, but again the complexity & consequent low reliability of rotary flight mechanisms seems to imply that balloons are a much better solution for UMSF applications.

The only real advantages helos have over balloons are speed & precision positioning (disregarding for a moment the vibration in choppers!). I think that a trade-off study between the two modes of travel for a mission to Mars or Titan would overwhelmingly favor balloons, if for no other reason than that a balloon is likely to survive far longer.

There's an even more simple design than helos and balloons, the tumbleweed rover! You can find more information here http://www.spacescience.com/headlines/y2001/ast17aug_1.htm

If this kind of "rover" works on Mars I think it will work on Titan too, with some modifications.

The worst case scenario for flying is Triton. Surface pressure is measured in micro-bars <1 bar approx 1 atmosphere>, not millibars, like Mars.

Triton has a REAL atmosphere. You can see limb hazes and the gyser-like plumes jet straight up some kilometers before making a right angle and blowing horizontally with the wind at altitude. But that's somewhere near the lower limit for anything you can call a "sensible atmosphere".

Mercury and the Moon have atmospheres, but they're collisionless gas molecules following parabolic trajectories through space between collisions with the surface. Exospheric atmospheres. I *think* some of the marginally spectroscopically detectable atmospheres on Europa, Ganymede, etc. are denser than exospheres so that there's molecular collisions above the surface, but they're not "real" atmospheres from a take-a-picture-and-see-it level like Triton's (and probably Pluto's)

Moved posts about Aerobraking at Triton

I just came across a photo of Zubrin's Gashopper under test:

Click to view attachment


Bob Shaw

So did someone else on page 1 of this thread.

Doug:

Flattery is the sincerest form of imitation!

Please zap the offending wossisname.



Bob Shaw

Looks like somebody forgot to forget the Mars airplane! LINK