Air Transportation on Mars - Gravity's affect on Air travel on Mars

kbd512 · 2016-10-10 22:28:12

A quad rotor with low blade loading should work. It would only be suitable for transporting two astronauts in MCP suits. There would need to be a rover waiting for the crew on the ground. This vehicle would have no electric motors or internal combustion engines, would contain very little metal, and would not be particularly crashworthy. A MTOW of perhaps .75t (285kg on Mars) should be achievable. It'll be radically different from anything flown on Earth.

Some characteristics of this quad rotor would be as follows:

* airframe components (fuselage, wings, rotor blades) constructed of graphene composites
* unpressurized cabin
* fabric bungee seating
* four small CO2 expansion driven piston or turbine engines
* composite liquid CO2 tank
* graphene polymer battery to store electrical power required to heat the liquid CO2 to a gas and distribute it to the engines
* heating elements convert the CO2 to a gas and then rapidly expand it using a substantial temperature change to increase pressure
* operating ceiling no higher than 1000M AGL or so
* skid landing gear

Google "EHANG 184" for a visual on what this helicopter might look like. The major difference would be mounting the rotors above vs below the fuselage to give the pilots better downward visibility. Turn the EHANG 184 upside down and that's similar to what it'd look like.

Astronauts could quickly explore interesting finds on the surface from a better equipped base by sending small robotic rovers out ahead of the helicopters to reduce travel time. The astronauts would then fly out to meet the rovers if an interesting find was discovered. The rovers would replenish the helicopter's CO2 tank and recharge the battery. After retrieval of samples, the helicopter would then fly the astronauts and their samples back to base for analysis. You could cover a lot more ground that way than you could if you had to travel by rover. There would also be a lot less duplication of functionality between the base and its pressurized rover.

elderflower · 2016-10-11 03:11:04

My rotor was nearly as big as the Fairey Rotodyne's but would lift only 4kN or so. I expect a bit more could be had using a better blade design for the conditions. That means it would just about lift itself and a fuel tank. I assumed HTP tip jets would be used. I don't think noise would be an issue on Mars, but sending 12 metre blades would.

GW Johnson · 2016-10-11 17:09:59

I tried to indicate the extreme inefficiency experienced with supersonic propellers back in 1945, on both sides of the war. There was even a version of the F-84 that attempted this in the 1950's. None ever worked worth a damn. Not one.

If you do a rotor blade or propeller on Mars, its tip speed must remain under Mach 1 (locally), or you will not achieve the aerodynamics that you want. Noise isn't an issue, so Mach 0.9+ tip speed is sort-of feasible. There will be local shocks over the suction-side airfoil surface, so you will start losing effectiveness at tip speeds above 0.9 Mach with thin airfoils, 0.8 Mach with thick airfoils.

Aerodynamics is a real bitch, ain't it?

GW

SpaceNut · 2016-10-11 18:27:06

Did quick search on the quad rotor helicopter https://en.wikipedia.org/wiki/Quadcopter and while these links are related to the RC field of toy ( images )there is no reason that they can not be made to work on mars if we use light wieght materials.
If you think ultra light type flying machine, we see that these are keeping with quite a variety of shapes and sizes. I could see this type being used with an MCP suit....

kbd512 · 2016-10-11 19:45:53

The design I had in mind would use compressed gas driven turbines connected to three-bladed contra-rotating blades. This is basically the same concept as the Sagita Sherpa, but doesn't use an internal combustion engine. There are 24 relatively short blades to provide lift while keeping tip speed below .8 Mach. Instead of increasing the length of the blades, which is not particularly helpful for our application, we're increasing the number of blades providing lift.

kbd512 · 2016-10-23 02:53:33

I did some quick number crunching and determined that the first (compressed CO2 powered rotor craft) and second concept (electrically powered rotor craft) I introduced were infeasible because the rotor blade / wing loading would be too high to achieve lift on Mars. However, there is an alternative that should actually work.

I'll start with the power plant, work through why rotor blades of any reasonable length won't work (for lifting two humans into the air), and then propose an alternative that should actually work. The alternative uses electric lift fans.

Concept #1 would weigh 285 kg on Mars, but the rotor blades could never lift it off the ground without the rotor blades going supersonic.

Concept #2 would weigh 166 kg on Mars, but the rotor blades could never lift it off the ground because the blade loading is too high. The particulars of this concept are listed below:

We need LENR reactor cavities that can withstand the QuarkX LENR’s operating temperature of 1500C, so we’d probably use Tungsten or some sort of Tungsten alloy.

Tungsten Melting Point: 3422C
Tungsten Density: 19.25gm/cm^3

QuarkX Power Core Dimensions: 3mm D x 30mm (graphene thermionic power converter)
QuarkX Reactor Tube Dimensions: 1mm D x 30mm L; .2mm tube thickness
QuarkX Reactor Tube Volume: 33.93mm^3 or .03393cm^3
QuarkX Reactor Tube Mass: 0.6531525gm
QuarkX Reactor Tube Power Output: 100Wt
QuarkX Power Core Power Output: 30We

The Zigolo air-cooled electric motor is a power plant developed and flown on light aircraft and ultralight aircraft. It is optimized to rotate at 2500rpm, which is very close to the 2400rpm that JPL’s Mars Helicopter Scout (MHS) demonstrator was intended to operate at, but gearing is required to contra-rotate propellers and it’s likely that we’d also using gearing to reduce rotor blade tip speed to Mars local .8 Mach.

Zigolo Electric Motor Mass: 11kg
Zigolo Electric Motor Power Output: 75hp, 55.9275 kWe

Quad Rotor Helicopter Requirements:

Mass of 500kg or less, based on JPL calculations about how much mass an electric motor helicopter can lift on Mars before the mass of the helicopter causes the rotor blade tip speed to exceed Mars local .8 Mach. Blade tip speed has to stay at or below .8 Mach for optimal efficiency, so blades have to be relatively short.

Mars Mach 1 is approximately 244.2m/s (879.3km/h), so .8 Mach is 195.4m/s (703.44 km/h)

S = d/t (Speed = distance / time)

C = pi * D (Circumference = 3.14 * Diameter)

Assuming Each rotor has a diameter of 3m

C = 9.42m

S = 9.42m * 1250rpm

S = 11,775m/minute or 196.25m/second or 706.5km/h

Our quad rotor masses detailed below indicate that the vehicle weighs 438kg on Earth, 166kg on Mars, so each rotor blade has to lift 6.935kg into the Air.

Each rotor blade would have an area of approximately .375m^2. This equates to an individual blade loading of 18.5kg/m^2. Based on my rough understanding of wing loadings capable of producing lift on Mars, an electric helicopter capable of lifting 166kg is infeasible.

The JPL Mars Helicopter weighs 1kg and its electric motor consumes 220We to lift 1kg to a maximum height of 600M above the surface of Mars. By extrapolating what would be required to lift 500kg, the power requirement is 110kWe. However, the four electric motors require a total of 240kWe. The extra power is required since each electric motor is swinging two larger 3 bladed contra-rotating rotors.

A quick review of the mass of each major system component is required to determine if we can keep the total mass below 500kg. The crew is assumed to consist of two 90 kg astronauts wearing 27kg MCP suits. Although each electric motor requires 60kWe, reserve power factor of 1.5 pushes the power requirement of each LENR power pack to 90kWe.

Two MCP suited astronauts: 234kg
4 Zigolo Electric Motors: 44kg
4 90kWe LENR power packs: 40kg (mass includes reactor cores and power conversion)

That’s 318 kg just for the astronauts, power, and propulsion requirements. The total mass of the airframe has to stay at about 100kg or so, and approximately 5kg worth of gearing is required for each motor to drive the contra-rotating blades. The airframe structural weight is only achievable with advanced composites, but achievable nonetheless.

Concept #2 was within the practical mass limit for a helicopter operating on Mars, whereas Concept #1 was not, but individual rotor blade loading was too high to produce lift.

kbd512 · 2016-10-23 03:52:53

Concept #3 uses four lift fans.

One 40kWe lift fan .9m in diameter rotating at 50,000rpm should produce approximately 1.7kN of thrust at Mars sea level, thus a single fan would be sufficient to lift the quad rotor craft described in concept #2. However, need four lift fans and each fan would be a bit smaller than the .9m lift fan of NASA's MIRAGE.

SpaceNut · 2016-10-23 08:31:08

For those that are trying to follow...
http://aviation.stackexchange.com/quest … r-diameter

What limits the speed at which the rotor can rotate? As the blade tip speed gets faster, drag increases with the square of the speed. Increased drag means increased power required which means heavier engine and heavier gearbox. As speed moves to a high percentage of supersonic, turbulence and therefore drag increases enormously. The longer the blade, the lower the possible rotor RPM since the tip approaches supersonic speed more quickly.
Why not just increase the length? Because the blade becomes increasingly difficult (and expensive) to manufacture to handle the loads on the blade and the heavier they become requiring more robust and heavier rotors hub assemblies.
The inner part of the rotor also produces little lift since it is moving relatively slowly and since lift decreases with the square of the speed, the lift generated falls away rapidly as you move to the inside portion of the disc. As you increase the length of the blade, without being able to increase the speed of the disc as above, the area of the disc which is "useless", increases as a proportion of the overall disc size. Therefore, more power is needed to rotate the increasingly large useless area of the disc.

http://www.helistart.com/RotorBladeDesign.aspx

This ratio depends on the design of the aerofoil, and before we go on to discuss a number of types, we will first introduce the fineness ratio. This is the thickness of the airfoil as a percentage of the chord length. A blade with a good L/D performance has a fineness ratio of about 15%, with its maximum chamber being a quarter of the way back from the leading edge. A typical L/D value for a helicopter blade is 30:1.

http://www.helicycle.com/BJ/q13.htm

What was the blade width as that would change speed of rotation and force for lift....

elderflower · 2016-10-25 02:39:21

Back again.
I started with the Fairey Rotodyne rotor as this is the biggest tip jet machine that I know of, and I know it worked. Using a tip jet drive simplifies the machine enormously. I then adjusted for mass flow through the rotor disc and restricted the tip speed to M0.85. I was looking for something that would lift two suited men and emergency supplies for two or three days, and bring back some samples. I got about 4000 Newtons lift which means a total mass on Mars of about 1.5 Te including machine, fuel, crew and payload. Design improvements for the conditions might increase this, so we might have the ability to design a marginal machine capability at 7 mBars, but a practical device at 11 or 12 mBars in the bottom of Hellas. This would allow much more effective exploration from a fixed base.
It's my understanding that increasing the number of blades in the rotor disc only reduces the loading per blade and has little effect on the overall lift so I didn't adjust this.

kbd512 · 2016-10-26 15:12:16

Elderflower,

With lift fans, the Mach problem that limits rotor blade lengths goes away. You have to spin the fans significantly faster, but that's not a major problem. With four or more lift fans, two or even four place harriers are entirely possible. Moreover, it's possible using existing electric motor and battery technology. LENR's just make harriers a highly practical, fast, and inexpensive method of travel on Mars.

Who really wants to be jostled around in a rover when they can fly to their destination?

The most attractive feature of the electric harrier is its low mass. A rover that could carry humans equivalent distances would have to be much heavier. Perhaps we should just have a home base, four two seat harriers, and eight small robotic rovers that can dig pits for inflatable tents with porta-potties.

That's probably the most efficient way to explore Mars. It'd definitely be faster. If a rover finds something worth investigating further, you fly out to meet it. If not, you stay at your base until it does. If we put the base within walking distance of a good ice supply, we have a nice little setup. Perhaps two rovers can stay at the base to carry ice blocks for water resupply.

elderflower · 2016-10-27 11:20:05

The object here is the mobility, not so much the means. To have a base and explore a radius of just a few kilometres (maybe 3 days travel in a surface rover) is just not productive enough. To extend it you would need a rover/hab (much bigger and more massive) or an aircraft of some kind. A quadcopter device with ducted fans might work but I've never seen one as big as I have in mind. Rocket powered hoppers are the fallback, but they aren't going to be very efficient for moving men, equipment and samples over a couple of hundred kilometres.
LENRs have a long way to go to be reliably useable on Earth, never mind on Mars, so I think we should stick with a tank of chemicals for a power source for our initial concepts.

SpaceNut · 2016-10-27 18:55:10

I see that the Fairey Rotodyne is an Ingenious Blend of Airplane and Helicopter to which it just might be the correct design as we can not use the speed in the air flow path for lift and the helicopter does just that so that the plane blades just control forward motion rather than cause it to create lift from air density.

kbd512 · 2016-10-28 09:40:11

SpaceNut wrote:

I see that the Fairey Rotodyne is an Ingenious Blend of Airplane and Helicopter to which it just might be the correct design as we can not use the speed in the air flow path for lift and the helicopter does just that so that the plane blades just control forward motion rather than cause it to create lift from air density.

Lift fans aren't used for helicopters here on Earth, apart from UAV's, because they're not as power-efficient as helicopters within certain operating parameters. However, without a ridiculous number of rotors and motors I can't come up with a feasible powered flight solution for humans.

Aurora Flight Sciences is developing electric lift fans with money from DARPA. Their 70kWe model developed 430 pounds of thrust in testing using a 32" fan.

Lake Matthew Team - Cole · 2016-12-26 16:31:25

Mars Magnus Aerobot

orionblade wrote:

The whole dirigible idea is probably the best, since you could have a big clear envelope lined on the bottom with flexible solar cells...

kbd512 wrote:

A quad rotor with low blade loading should work.

You could say Ravindran et al. combined and extended those two ideas in their Mars Magnus Aerobot Preliminary Design.

It's a PV dirigible with rotors, and also a Magnus lift rotator. The design is interesting because of its high payload: Magnus lift is about 5x the lift of the dirigible hydrogen. Net net: at mean surface level their 70 kg design gives a total lift of 236 N, not counting lift from rotors. That's adequate for an instrument payload. Conceivably larger or teamed aerobots might serve as crew transports. One limitation: their design does not produce enough PV electrical power for continuous operation.

The design is an adaptation of the 1982 Magnus Spherical Airship.

Terraformer · 2016-12-26 17:44:06

How does using the Magnus effect compare with rotors?

Lake Matthew Team - Cole · 2016-12-26 18:22:25

Terraformer wrote:

How does using the Magnus effect compare with rotors?

Magnus effect gives greater lift. In comparison, the proposed JPL Mars copter is a kind of rotor, augmented. It would mass 1 kg and spin a counterrotating rotor pair having span of 1.1 m.

With the rotor spinning at 2400 rpm, the copter lifts only itself and a payload of, essentially, a GoPro camera board. Rotor tips approach 500 km/hr, so there's little freedom to increase rpm or blade length. Payload is maxed out.

kbd512 wrote:

...without a ridiculous number of rotors and motors I can't come up with a feasible powered flight solution for humans.

Given the very slight lift of JPL's example copter, I think kbd512 is probably right on that.

Last edited by Lake Matthew Team - Cole (2016-12-27 16:36:28)

SpaceNut · 2016-12-27 22:45:46

Lake Matthew Team - Cole, I really need to say thank you for posting to the many topics and welcome to NewMars. Thanks for the links Mars Magnus Aerobot posts as this was something I have not seen before.....

Lake Matthew Team - Cole · 2016-12-28 10:43:28

SpaceNut wrote:

Lake Matthew Team - Cole, I really need to say thank you for posting to the many topics and welcome to NewMars...

Well hi, and thanks for running things. Sane forum.

kbd512 · 2016-12-28 18:39:34

Lake Matthew Team - Cole,

If I understand correctly the 70kg (on Earth or Mars?) demonstrator produces 24kg of lift. However, it's a lighter-than-air vehicle, so the excess lift can be used to accelerate or change altitude. Is that correct? Any estimate on achievable flight speeds?

Lake Matthew Team - Cole · 2016-12-28 19:57:23

kbd512 wrote:

If I understand correctly the 70kg (on Earth or Mars?) demonstrator produces 24kg of lift. However, it's a lighter-than-air vehicle, so the excess lift can be used to accelerate or change altitude. Is that correct? Any estimate on achievable flight speeds?

Their example aerobot has 70 kg vehicle mass and 64 kg payload, on Mars at mean surface level. Ceiling +2 km, max speed 5 m/s.

Last edited by Lake Matthew Team - Cole (2016-12-28 20:12:08)

SpaceNut · 2016-12-28 21:18:28

The attachment points for the basket seem to be very weak in that they would rip the materials making up the balloon so why not continue the bridle around the top as well. The solar cells would appear to be the flexible plastic substrate design down around the 8 - 15% effiecency. I would think we would want to use the suns thermal energy to create lift from heating the balloon so why so much white surface as Black would make this possible.
Whats funny is there is a balloons on mars topic....
will look for it later....

Lake Matthew Team - Cole · 2016-12-28 22:26:49

Mars Magnus Aerobot

SpaceNut wrote:

The attachment points for the basket seem to be very weak...

It's not obvious from the conceptual illustrations that the balloon is attached. See the gap? Ravindran's drive train might be connecting across that gap via magnetic linkage.

SpaceNut wrote:

...why not continue the bridle around the top as well...

That would cause turbulence on the upper surface, killing lift.

SpaceNut wrote:

...use the suns thermal energy to create lift from heating the balloon...

It's a super-pressure balloon: constant volume and shape. Therefore heating doesn't increase lift. Conversely, constant volume makes constant-elevation travel much easier. Also the constant volume and shape hold the balloon's lower surface constantly close to the bodyshell. According to the original Ferguson patent, this reduces drag and improves maneuverability.

Void · 2016-12-29 19:56:42

Lake Matthew Team - Cole,

If you are still out there, and you wish to I would like to know where the low pressure and high pressure are exhibited on this flying machine when it is running on Mars or Earth.

In other words how does the machine get sucked up vertically or pushed up vertically through it's mechanical efforts?

I have looked through the internet, and it is still unclear to me.

Last edited by Void (2016-12-29 19:57:28)

Lake Matthew Team - Cole · 2016-12-29 20:50:55

Void wrote:

I would like to know where the low pressure and high pressure are exhibited on this flying machine when it is running on Mars or Earth.
In other words how does the machine get sucked up vertically or pushed up vertically through it's mechanical efforts?
I have looked through the internet, and it is still unclear to me.

Faster flow above the rotator results in downward flow deflection and corresponding upward Magnus force. La Wik.

Sketch_of_Magnus_effect_with_streamlines_and_turbulent_wake.svg

Void · 2016-12-29 21:25:35

Thank you.

So the friction of the surface of the spinning "Balloon" as the device travels forward, creates the lift as you describe.

Don't get upset if I ask a question that requires a negative answer, but here it is:
"Could the lift be increased by gripping the atmosphere on the upper portions of the balloon with electrostatic cling, and that electrostatic cling stimulation reduced/eliminated on the lower portion of the balloon?"

I can think of several ways to manipulate the electrostatic cling on the interior or exterior of the balloon, but for now let me suggest a commutator type situation with very thin bands of conductive material as part of the balloon structure.

Of course this will impose an unknown power burden, which likely will be additional to the original, but of course if it created more lift, that cost might be worth it.

Last edited by Void (2016-12-29 21:26:59)

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Re: Air Transportation on Mars - Gravity's affect on Air travel on Mars

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