[X] My Assistant

[ynyralmaen]

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"

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?

[Tom Ames]

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?

[Paolo]

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

[helvick]

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.

[ngunn]

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.

[Guest_Myran_*]

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.

[nprev]

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...

[edstrick]

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

[Bob Shaw]

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...

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


Bob Shaw

[tty]

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.

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

[tty]

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

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

[djellison]

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

[nprev]

...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.

[edstrick]

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

I LOVE it!

[Bob Shaw]

...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.

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