APOD: Ingenuity on Sol 39 (2021 Apr 03)

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APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by APOD Robot » Sat Apr 03, 2021 4:06 am

Image Ingenuity on Sol 39

Explanation: The Mars Ingenuity Helicopter, all four landing legs down, was captured here on sol 39 (March 30) slung beneath the belly of the Perseverance rover. The near ground level view is a mosaic of images from the WATSON camera on the rover's SHERLOC robotic arm. Near the center of the frame the experimental helicopter is suspended just a few centimeters above the martian surface. Tracks from Perseverance extend beyond the rover's wheels with the rim of Jezero crater visible about 2 kilometers in the distance. Ingenuity has a weight of 1.8 kilograms or 4 pounds on Earth. That corresponds to a weight of 0.68 kilograms or 1.5 pounds on Mars. With rotor blades spanning 1.2 meters it will attempt to make the first powered flight of an aircraft on another planet in the thin martian atmosphere, 1 percent as dense as Earth's, no earlier than sol 48 (April 8).

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Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by orin stepanek » Sat Apr 03, 2021 1:03 pm

PIA24449_1024.jpg
Beautiful! Like a mother standing over her child; Perseverance over ingenuity! :lol2:
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Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by Cousin Ricky » Sat Apr 03, 2021 2:31 pm

APOD Robot wrote:
Sat Apr 03, 2021 4:06 am
Ingenuity has a weight of 1.8 kilograms or 4 pounds on Earth. That corresponds to a weight of 0.68 kilograms or 1.5 pounds on Mars.
On Mars, Ingenuity will have a mass of 1.8 kilograms. Even your links make that clear. I don’t know that “weight in kilograms” has any meaning outside our informal usage in an earthbound context. Even on Earth, the ratio of kilogram to pound varies depending on location.

Perhaps we should teach the general public—at least those who are willing to go metric—about newtons?

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Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by Chris Peterson » Sat Apr 03, 2021 3:17 pm

Cousin Ricky wrote:
Sat Apr 03, 2021 2:31 pm
APOD Robot wrote:
Sat Apr 03, 2021 4:06 am
Ingenuity has a weight of 1.8 kilograms or 4 pounds on Earth. That corresponds to a weight of 0.68 kilograms or 1.5 pounds on Mars.
On Mars, Ingenuity will have a mass of 1.8 kilograms. Even your links make that clear. I don’t know that “weight in kilograms” has any meaning outside our informal usage in an earthbound context. Even on Earth, the ratio of kilogram to pound varies depending on location.

Perhaps we should teach the general public—at least those who are willing to go metric—about newtons?
"Weight" is formally defined as the force on a body due to gravity. In conventional scientific units, weight is given in newtons. It can certainly be expressed in pounds, but in that case the proper unit is "pounds-force". A mass of 1.8 kg corresponds to a Martian weight of 0.68 kg-force or 1.5 lbs-force.

On any non-uniform body, the gravitational field varies with location, so the conversion from mass to weight will vary. But the ratio of kg-force to lbs-force doesn't ever change.
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MottyGlix

Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by MottyGlix » Sat Apr 03, 2021 6:31 pm

Cousin Ricky is right. If this site is to be in any way educational, it must teach the difference between weight and mass. Certainly, the founders of the metric system had this in mind when they made separate units for mass and force. Using the ignorance of the masses as a justification for yourself using bad terminology is a very poor excuse.

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Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by Chris Peterson » Sat Apr 03, 2021 6:42 pm

MottyGlix wrote:
Sat Apr 03, 2021 6:31 pm
Cousin Ricky is right. If this site is to be in any way educational, it must teach the difference between weight and mass. Certainly, the founders of the metric system had this in mind when they made separate units for mass and force. Using the ignorance of the masses as a justification for yourself using bad terminology is a very poor excuse.
Non-metric (SI) systems also use different units for mass and force. The problem is less one of units than it is an actual understanding of how weight is different from mass. As you say. (It's one of the things I spend time on in the classroom. And no matter how often I go over it, people forget it. A problem caused, I think, by the simple reality that in almost all cases, the value for mass and for weight is the same. Maybe one day, when we've adapted to living off the Earth...)
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heehaw

Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by heehaw » Sat Apr 03, 2021 10:23 pm

Units! We should all switch to natural (nature's) units. Look at page 2 of this! https://henry.pha.jhu.edu/speedlimit2.pdf

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Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by VictorBorun » Sun Apr 04, 2021 6:05 pm

Our geocentric units long since got insufficiently precise. So what?
We never abandon them, just re-define in a more precise way.

Meter used to be 1 / 40 million of the Parisian meridian.
Gram used to be the mass of 1 cubic centermeter of water at the temperature near 0°C where the density peaks.
Second used to be 1 / 24 / 3600 of a mean solar day.

They all are re-defined now.

Mean gravity g at Earth surface in rotating reference system can be re-defined as precise as we need.
So we can well use a kilogram weight as a unit of force, 1 kg weight = 1 kg * g.

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Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by Chris Peterson » Sun Apr 04, 2021 6:13 pm

VictorBorun wrote:
Sun Apr 04, 2021 6:05 pm
Our geocentric units long since got insufficiently precise. So what?
We never abandon them, just re-define in a more precise way.

Meter used to be 1 / 40 million of the Parisian meridian.
Gram used to be the mass of 1 cubic centermeter of water at the temperature near 0°C where the density peaks.
Second used to be 1 / 24 / 3600 of a mean solar day.

They all are re-defined now.

Mean gravity g at Earth surface in rotating reference system can be re-defined as precise as we need.
So we can well use a kilogram weight as a unit of force, 1 kg weight = 1 kg * g.
A kilogram weight is a unit of force. By definition.
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Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by neufer » Sun Apr 04, 2021 11:31 pm

Click to play embedded YouTube video.
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Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by MarkBour » Mon Apr 05, 2021 8:32 am

Cousin Ricky wrote:
Sat Apr 03, 2021 2:31 pm
APOD Robot wrote:
Sat Apr 03, 2021 4:06 am
Ingenuity has a weight of 1.8 kilograms or 4 pounds on Earth. That corresponds to a weight of 0.68 kilograms or 1.5 pounds on Mars.
On Mars, Ingenuity will have a mass of 1.8 kilograms. Even your links make that clear. I don’t know that “weight in kilograms” has any meaning outside our informal usage in an earthbound context. Even on Earth, the ratio of kilogram to pound varies depending on location.

Perhaps we should teach the general public—at least those who are willing to go metric—about newtons?
Valid points. But I want to make sure that the relevance of the APOD's exact opposite emphasis is not lost on readers.
Note the end of the sentence in the APOD caption: "it will attempt to make the first powered flight of an aircraft on another planet in the thin martian atmosphere, 1 percent as dense as Earth's."

So, those blades are going to have to generate enough lift to get this vehicle airborne in an atmosphere that is hardly there. The one thing that is acting in its favor, is that it will only have to generate force to counteract 0.38 G (3.721 m/s2).

I'm pretty sure it will lift off and fly well, because I've great confidence in NASA's engineers to have everything figured out.
Today would have been a great day to have tried it. After all, the date of this APOD is 4 ... 3 ... 21 . [ :D ]
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Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by VictorBorun » Mon Apr 05, 2021 10:08 am

APOD Robot wrote:
Sat Apr 03, 2021 4:06 am
The Mars Ingenuity Helicopter, all four landing legs down.
At the first look it seems scary, the way the car is sitting down so the copter's legs almost scratch the ground.
At the second look you notice the shadow cast by the right background leg and know that there is in fact a gap.

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Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by Chris Peterson » Mon Apr 05, 2021 1:16 pm

MarkBour wrote:
Mon Apr 05, 2021 8:32 am
Cousin Ricky wrote:
Sat Apr 03, 2021 2:31 pm
APOD Robot wrote:
Sat Apr 03, 2021 4:06 am
Ingenuity has a weight of 1.8 kilograms or 4 pounds on Earth. That corresponds to a weight of 0.68 kilograms or 1.5 pounds on Mars.
On Mars, Ingenuity will have a mass of 1.8 kilograms. Even your links make that clear. I don’t know that “weight in kilograms” has any meaning outside our informal usage in an earthbound context. Even on Earth, the ratio of kilogram to pound varies depending on location.

Perhaps we should teach the general public—at least those who are willing to go metric—about newtons?
Valid points. But I want to make sure that the relevance of the APOD's exact opposite emphasis is not lost on readers.
Note the end of the sentence in the APOD caption: "it will attempt to make the first powered flight of an aircraft on another planet in the thin martian atmosphere, 1 percent as dense as Earth's."

So, those blades are going to have to generate enough lift to get this vehicle airborne in an atmosphere that is hardly there. The one thing that is acting in its favor, is that it will only have to generate force to counteract 0.38 G (3.721 m/s2).

I'm pretty sure it will lift off and fly well, because I've great confidence in NASA's engineers to have everything figured out.
Today would have been a great day to have tried it. After all, the date of this APOD is 4 ... 3 ... 21 . [ :D ]
Yes, it will make the first powered flight on another planet. But hardly the first powered flight in the martian atmosphere, given that this device and its prototypes were certainly tested extensively in a large chamber on Earth that duplicates the conditions it currently finds itself in.
Chris

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King_Nothing

Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by King_Nothing » Mon Apr 05, 2021 8:16 pm

Wouldn't you consider the decent stage (sky crane) controlled (powered) flight?

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Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by MarkBour » Tue Apr 06, 2021 8:44 pm

King_Nothing wrote:
Mon Apr 05, 2021 8:16 pm
Wouldn't you consider the decent stage (sky crane) controlled (powered) flight?
Or was it "falling with style"?

Click to play embedded YouTube video.

Seriously, though, you have a point. So technically, perhaps the APOD should say: first powered takeoff, controlled flight, and soft landing, using lift from the atmosphere (?)
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King_Nothing

Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by King_Nothing » Wed Apr 07, 2021 1:43 pm

MarkBour wrote:
Tue Apr 06, 2021 8:44 pm
King_Nothing wrote:
Mon Apr 05, 2021 8:16 pm
Wouldn't you consider the decent stage (sky crane) controlled (powered) flight?
Or was it "falling with style"?

Click to play embedded YouTube video.

Seriously, though, you have a point. So technically, perhaps the APOD should say: first powered takeoff, controlled flight, and soft landing, using lift from the atmosphere (?)
Your description would be more accurate I would think but, that was DEFINITELY falling with style!

I still think they should have landed the sky cranes, as opposed to crashing them. They have clearly demonstrated the ability to bring them to a controlled stop. I understand their thinking in just getting them as far away as possible but, you still run the risk of explosion debris which would would travel a lot farther under the (almost) non-existent atmosphere and lower gravity. The first one had considerably more fuel leftover than they thought it would after dropping Curiosity, so that (probably) wouldn't be a problem.

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Re: APOD: Ingenuity on Sol 39 (2021 Apr 03)

Post by MarkBour » Fri Apr 09, 2021 1:16 am

King_Nothing wrote:
Wed Apr 07, 2021 1:43 pm
I still think they should have landed the sky cranes, as opposed to crashing them. They have clearly demonstrated the ability to bring them to a controlled stop. I understand their thinking in just getting them as far away as possible but, you still run the risk of explosion debris which would would travel a lot farther under the (almost) non-existent atmosphere and lower gravity. The first one had considerably more fuel leftover than they thought it would after dropping Curiosity, so that (probably) wouldn't be a problem.
NASA is very good at thinking of ways to get something extra out of a mission, but maybe they didn't think along that line hard enough in this case. I think SpaceX would surely have tried to land them (but not on a drone ship :-) ) and even given them something to do when they got there.
Mark Goldfain