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#51 2019-03-15 21:28:30

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 16,141

Re: Scouting Mars by Helicopter

The back wake and forward motion of a helicopter blade is accomplished by it angling with speed to change the force of uplift with regards to speed of the blades rotation. That is something that a regular fan blade does not do as its fixed. Its the size of that surface area that for mars which is increased. The blade creates the force by moving cubic feet per second or meters per second by the screw motion of the blade.

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#52 2019-03-16 06:49:45

kbd512
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Registered: 2015-01-02
Posts: 2,957

Re: Scouting Mars by Helicopter

tahanson43206,

The WhalePower website lists a number of published science articles between 2012 and now under the link entitled "Scholarly Articles".  That would be research performed by other people, rather than their own.

Then there is this little technology that DARPA / USAF / NASA funded:

FlexFoil Compliant Control Surfaces

Check out the section entitled "Active Surface Flow Control".

Why are these two technologies important?

The tubercles provide increased CL at increased angles of attack without a corresponding increase in CD.

The adaptive compliant surface technology from FlexSys provides a means to alter (increase or decrease) CL for individual blades independent of the others.  Amongst other things, NASA has created pressure transducers from Graphene and CNT materials so that a sensor can actively sense and adjust to pressure changes.  Why not try electrically adjustable airfoils?  Obviously the applications of those technologies require thorough testing to assure that the lift produced is consistent for the advancing and retreating blades.

This company seems to understand what must be done to optimize fixed pitch prop tips to reduce drag:

Prince Aircraft Company - The Prince P-Tip Propeller

Nature provides free science lessons for anyone willing to learn.  The engineering?  Well, that'll cost you a bit.  I think it's worth it, though.  I see this as a win-win for aviation in general, but also wind turbines and helicopter rotors in particular.  There's no downside to discovering the limits of what we can do with these technologies, especially in combination to control blade loading to reduce vibration from turbulence.

I want to know if CLα can be dynamically altered for different individual blades, dependent upon position.  Theoretically, we could produce blades with independently variable chord and camber lines to alter (deform) the suction and pressure surfaces.  Clα could even be varied across the airfoil's span to some degree to contend with gust loads, although that's more applicable to wind turbine blades.  FlexSys has already proven that this can be done many times per second to dampen flutter.  There should be at least three potential money-saving uses from merging these applications of aeroelastic surfaces and flow control aerodynamics.

Someone get that XF-84H out of the bone yard and let's take a second crack at it.

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#53 2019-03-16 10:59:57

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,643
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Re: Scouting Mars by Helicopter

Tahanson43206:

The physics of (low speed) incompressible fluid flow is vastly different from that in supersonic compressible flow.  Even the basic flow patterns are vastly different.  That's why the preferred shapes are different.

I am aware that the knobby whale fin leading edge took people by surprise as to its effectiveness,  but that's at a few-to-several meters per second in essentially-incompressible water flow.  It might work in helicopter rotors,  but only if you stay away from compressible high-subsonic flow,  and it has little-or-no potential at all in supersonic flow (those knobs shedding complicated shock waves). 

As to speed of sound and Mach number,  the formula for calculating speed of sound depends upon temperature and gas properties.  Mach number M = V/c,  where V is velocity and c is speed of sound.  c is not a constant.  Gas properties are,  but temperature is not.

For flow analysis by ideal gas models where the PV = RT equation of state applies,  c = (g gc R T)^0.5,  where g is the specific heat ratio for the gas (for Earthly air at ordinary temperatures,  use g = 1.40,  but for triatomic CO2 as Mars "air" use g = 1.33).  The gc is the gravity constant if your units of measure are not consistent (32.174 for US customary lbm mass units with lb force units,  9.8067 if you use German kgf force units with kg mass units,  and 1 if using SI kg mass units with Newtons).  R is the gas constant obtained by dividing the universal molar gas constant by the molecular weight of the gas (28.97 for Earthly air,  pretty close to CO2's 44 for Mars "air").  The temperature T is the absolute-scale temperature measurement:  deg K if metric,  deg R if US customary;  K = C + 273.15,  R = F + 459.67).

On Earth at T = 59 F = 15 C = 518.67 R,  using g = 1.40,  MW = 28.97,  univ Ru = 1545.4 ft-lb/lbmol-R,  I get R = 53.34 ft-lb/lbm-R, and c = 1116 ft/sec = 340.3 m/s for you metric guys. Up in the cold stratosphere at -70 F,  I get 967.3 ft/sec = 294.8 m/s.  Same as that right out of the standard atmosphere tables. 

On Mars at T = -40 F = -40 C = 419.67 R,  I get R = 35.1 ft-lb/lbm-R and c = 794.2 ft/sec = 242.1 m/s.  Up higher where it is much colder,  say -100 F = -73 C,  I get c = 735 3 ft/sec = 224 m/s.

On your typical subsonic airfoil,  even with a thin section,  you get into compressibility troubles and local shock formation at a Mach number in the 0.8 to 0.9 range.  You get some sort of bow shock formation and serious flow separation troubles at Mach 1.  The diamond or double-wedge shapes that work better at supersonic speeds are really crappy as airfoils when flown subsonically,  which is why supersonic fighter jets have such high takeoff and landing speeds,  even with airfoils that are a compromise of the two shape classes.

Consider this:  on every rotor or propeller,  there is a linear variation of rotational speed from max at the tip to zero at the centerline of the hub.  This rotational speed adds vectorially,  usually (but not always) at 90 degrees,  with the oncoming flight speed,  to produce the actual wind speed and direction-relative-to-chord-line at every station along the blade. 

This is where the blade twist distribution must come from,  as a compromise across the expected range of flight speeds,  and complicated by variable-pitch capability,  if present.

It is also where the local oncoming Mach number distribution along the blade comes from,  which varies quite strongly with oncoming flight speed as well as rpm.  How the blade responds to that Mach varies strongly with twist distribution,  pitch setting,  and the distribution of local airfoil shape and thickness along the blade.

My point is that there are no simple formulas to use to "run some quick numbers".  There's many linked formulas,  and they are not simple.  And they are dependent upon data that are distributions of numbers,  not just single umber items.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#54 2019-03-16 11:05:11

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,643
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Re: Scouting Mars by Helicopter

Kbd512: 

Yep,  they tried supersonic props on the XF-84H.  They didn't like the results.  No better performance,  dangerous levels of noise. 

The Russian let the tips of the props go slightly supersonic on the Bear bombers at redline max power.  It didn't help hardly at all to increase takeoff power,  and it cost a lot of fuel at the reduced efficiency. 

The noise could be heard inside a submerged submarine at periscope depth,  with Bear passing overhead at low altitude.  And they certainly did not cruise with supersonic tips,  that was just emergency takeoff power.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#55 2019-03-16 15:37:42

tahanson43206
Member
Registered: 2018-04-27
Posts: 1,052

Re: Scouting Mars by Helicopter

For kbd412 #52
For GW Johnson #53

Thanks to each of you for detailed reply for study!

For SpaceNut #51 Thanks for reminder about changing the angle of attack on the rearward stroke.  I had forgotten about that.

The fun part of this discussion is that it will be possible to find out if NASA's vacuum chamber experiments will prove successful on Mars.

For SpaceNut ... I note that the proposed Mars drone design features counter rotating props, which (I assume) deals with part of the back swing problem, by insuring there is a forward thrust in progress to compensate for lost thrust during the back swing.

One thing worth noting is that if the Mars concept proves successful, then high altitude flight on Earth should follow.  Amazon might be able to deliver oxygen bottles to Everest climbers, for example.

As a reminder, in the Analog story about climbing Mount Olympus, high altitude drones were included as a significant plot element.

Edit: For the record, I went back and read the entire topic, from the first post by SpaceNut ... not much has chanced in the several years since. The description of the helicopter and its planned performance are about the same, and the participants in the topic are the same, except for void, who has not appeared in this topic in recent times.

I did note that GW Johnson was skeptical in the beginning, and remains so through his most recent post.   I gather that this undertaking is truly bleeding edge engineering!  Still, for the design to have held steady over several years, while electronics have advanced to improve performance and capabilities, seems encouraging to me.  2020 is not that far off. 

(th)

Last edited by tahanson43206 (2019-03-16 19:44:08)

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#56 2019-03-17 10:04:42

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,643
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Re: Scouting Mars by Helicopter

Yep,  I'm an open-minded skeptic about most new technologies,  with emphasis on the "skeptic" part.  That is because,  over the decades,  I have seen so many news releases trumpeting "breakthroughs" that were not. 

A couple of examples I have heard with my own eyes and ears:  Nuclear fusion power plants have been "10 or 15 years away" since the late 1950's.  Scramjet engines have been ready to fly us anywhere so fast,  and only 10-15 years away,  since the early 1960's.  There's many more.

Marketing ballyhoo in a press release is simply not a measure of technological readiness-to-apply.  That is the real lesson here.

And yet new things really do get done.  Just not as many as the press releases would have you believe.  The Saturn-5 was one.  The nuclear submarine was another.  The Saturn-5 took just over a decade to go from a paper concept to launchable hardware,  under a budget-is-no-problem environment.

GW

Last edited by GW Johnson (2019-03-17 10:05:39)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#57 2019-03-25 10:47:12

elderflower
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Registered: 2016-06-19
Posts: 1,115

Re: Scouting Mars by Helicopter

I made a spreadsheet and studied an existing large helicopter rotor design's performance under Mars conditions. It would struggle to lift a couple of men. If somebody comes up with a practical supersonic rotor a large helicopter could function on Mars, without this we will be limited to very small light drone type machines. Useful with cameras or other light science apparatus, but will not provide the sort of logistic facility to which we are accustomed on earth.

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#58 2019-03-25 11:38:57

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,643
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Re: Scouting Mars by Helicopter

I see in some press releases that NASA plans to send some sort of helicopter drone to Mars with the 2020 mission.  They must have some reason to think it's going to work. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#59 2019-03-29 12:20:07

tahanson43206
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Registered: 2018-04-27
Posts: 1,052

Re: Scouting Mars by Helicopter

Adding to GW Johnson's post #58:

https://techcrunch.com/2019/03/28/mars- … yptr=yahoo

It appears that the test compensated for the difference in gravity by lifting the test article with a thread.

The elevation used for data collection was 2 inches.  More elevation was (said to have been) not needed.

I think odds of the device working on Mars are about 80%, if it could be delivered there instantaneously.  However, my estimate of the probability of the entire experiment succeeding is about 50%, taking into account launch risks, travel risks, landing risks, and experiment deployment risks.

(th)

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#60 2019-03-30 13:06:44

kbd512
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Registered: 2015-01-02
Posts: 2,957

Re: Scouting Mars by Helicopter

All,

NASA's Mars helicopter completes flight tests

I'm pretty sure it's going now.  It has 1,500 parts in it, though, meaning that's one complicated little machine.  If it makes 1 successful flight and returns its findings to the rover, I'll consider that to be an unqualified success and a boon to future robotic and human exploration missions.  Anything after that is just icing on the cake.

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#61 2019-03-30 19:54:42

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 16,141

Re: Scouting Mars by Helicopter

They could have even placed helium in any of the sealed legs to ofset the mass of the vehicle to simulate that mass which would be seen on mars as well as the lifting string on a crane style winch which is the oposite of what was used to lower the rovers to mars when using the skycrane.

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#62 2019-03-31 04:01:36

elderflower
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Registered: 2016-06-19
Posts: 1,115

Re: Scouting Mars by Helicopter

It lifted itself but how much payload could it manage. Maybe that was included as on board instruments. Can it fly fast enough to overcome Mars breezes? Can it get back into its housing on the rover to avoid exposure to dust devils and Martian storms.

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#63 2019-03-31 17:56:42

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 16,141

Re: Scouting Mars by Helicopter

I have created a new topic for further discusion within, Mars Co2 or other compressed Gas Hopper rocket

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#64 2019-04-03 18:49:13

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 16,141

Re: Scouting Mars by Helicopter

I believe this was in some topic Cold Gas thruster testing using Quadcopter?

quadcopterdrone580x330.jpeg

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#65 2019-04-03 18:56:33

tahanson43206
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Registered: 2018-04-27
Posts: 1,052

Re: Scouting Mars by Helicopter

For SpaceNut #64 ... Thanks for the link you provided ... I followed it until I found a live feed to Sarah's paper:

https://dspace.mit.edu/handle/1721.1/67069

The paper is (apparently) downloadable as a pdf.

(th)

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#66 2019-04-03 19:37:11

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 16,141

Re: Scouting Mars by Helicopter

I was thinking about this solar powered mass on the nasa helicopter.

Another could be an RF power transmission scheme for the craft to get power from in order to go the distance on a fixed path.

tahanson43206 wrote:

You can find it by entering the search string shown below, without spaces:

S e a r c h T e r m :  and  : D e s i g n C O 2 P i z z a D r o n e

Author: tahanson432

***
The suggestion of a supply of power to the drone is interesting as well, although I was imagining that battery power on board the vehicle would be sufficient for a round trip time of one hour.  Can you expand a bit on your idea of RF power supply for the vehicle, and how you would use it.

The helicopter would pickup the power from a platform via the legs much like the pad for charging a cellphone. This would remove mass for gaining a higher level of altitude and flight time as well. The platform pad would have solar panels and batteries to charge while the helo is in use. Once it re-lands on the pad it would begin recharging for rapid reuse.
Another part to this is the platform pads could be designed for the unit to bring to other locations and with modular build stay within the lift capacity of the helo. String the recharge stations to gain further and further distance of exploration around the base.

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#67 2019-04-03 22:10:29

SpaceNut
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#68 2019-06-08 18:26:05

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 16,141

Re: Scouting Mars by Helicopter

NASA is putting the finishing touches on its Mars helicopter

pia23151-16.jpg?quality=98&strip=all&w=782

The tiny copter will be affixed to the belly of the Mars 2020 rover during the flight to Mars and throughout the landing phase. Once the rover is on the surface, it will deploy the helicopter.

The helicopter doesn’t have any scientific objectives this time around, and it’s being sent to Mars simply as a testing and demonstration vehicle to provide scientists with information on flight within the thin atmosphere of Mars.

The helicopter’s sole instrument is a high-resolution camera that, NASA hopes, will capture some lovely shots of the Red Planet and relay them back to Earth.

In the future, helicopter-like vehicles may be a regular addition to Mars missions since they afford greater flexibility to relocate to new areas in short periods of time.

JPL Blog Post website

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#69 2019-07-21 09:11:58

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 16,141

Re: Scouting Mars by Helicopter

What might seem as off topic

SpaceNut wrote:

The physics equation is the same for both the moving vehicle being pelleted and the moving dust/sand doing the blasting....the difference is which number goes where in the equation...

Are Martian Dust Storms Dangerous?

NASA’s Viking landers clocked them at 100 km/h during dust storm season. Which is a thing on Mars. The landers sheltered enough from the big storms that they probably didn’t experience the greatest winds they’re capable of.

When the wind is above 65 km/h, it’s fast enough to pick up dust particles and carry them into the atmosphere encasing the planet in a huge, swirling, shroud.

not as slow as you had thought

That momentum comes from air particle density and their velocity. Sadly, the density of the atmosphere on Mars is a delicate 1% of what we’re used to. It’s got the velocity, but it just doesn’t have the density.

It’s the difference between getting hit by a garden hose and a firehose with the same nozzle speed. One would gets you soaked, the other can push you down the street and give you bruises.

To feel a slight breeze on Mars similar to Earth, you multiply the wind speed by 10. So, if the wind was going about 15 km/h here, you’d need to be hit by winds going about 150 km/h there to have the same experience.

ouch!!!

Sandblasting winds shift Mars' landscape

"In our study area, sand-moving wind occurs almost daily" throughout much of the year, "Winds on Mars can be strong and can reach hurricane speed (more than 120 kilometres per hour or 75 miles per hour),"

Understanding the characteristics of Mars' winds would allow scientists to make predictions about the rate of erosion of the landscape and about the martian climate, which is heavily influenced by dust in the atmosphere.

This is one of the cautions for using air flight on mars.

The base numbers are also there for the speed of a plane and for bouyancy of mars lift...

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#70 2019-07-21 22:02:46

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 16,141

Re: Scouting Mars by Helicopter

I was in a local walmart and spied the q wireless cell phone charging plate. What shocked me was how much energy went in versus what could be recieved for charging. The particular unit required 5 Volt at 2 amps (10w) and what it would create for the cell phones charging was 5 Volt but at 1 amp only 5 W .

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#71 2019-07-22 07:27:48

tahanson43206
Member
Registered: 2018-04-27
Posts: 1,052

Re: Scouting Mars by Helicopter

For SpaceNut .... re #70

Off Topic << grin >> ... Please consider moving this to the new topics topic I created.

That said, your post inspired me to investigate a bit, and I read a number of customer reviews of products that looked similar to the one you described.

Summing up ... there are a few rave reviews, but the majority of customer reviews were on the complaint or unhappy side of the ledger.

With regard to your specific observation ... I'm not an engineer but I've hung around with them, and (in this case), specifically electrical engineers in RF specialties.  My (somewhat) educated guess is that the system has to post voltage significantly to generate an RF signal that can propagate to the phone.

What is surprising is that the engineers of THIS product were (apparently) able to achieve 50% efficiency.  That is amazing!

Thanks for your interesting post!

(th)

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#72 2019-07-22 20:40:56

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 16,141

Re: Scouting Mars by Helicopter

The device needing to charge needs 2 Amps, when its near dead of power in the battery and that is why the 1 Amp does not work out so well. Converting DC to AC for RF signal and then back to DC is why there is so much loss that plus an AC signal is a 50% duty cycle sine or square wave shaped wave of energy that is transmitted. The larger the gap between the charging pad and the device means less energy will be transferred.

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