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The Mars Helicopter Is Online and Getting Ready to Fly

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Re: The Mars Helicopter Is Online and Getting Ready to Fly

#201

Post by thaumasiotes »

simcop2387 wrote: post #181
xadhominemx wrote: post #180

Earlier quoted context omitted.

Venus’s atmosphere is 100x denser than earth’s, so you could just seal the metal balloons at sea level pressure and it wouldn’t really make a difference. Or you could seal them in a vacuum on earth. Not sure why you would need to feel them in space.

Weight and volume. The air has weight so it'll cost more to launch. The volume would also make them more difficult to launch. Assembling or unfolding in space near earth would allow you to make them larger and inspect them before they leave for venus.

> Assembling or unfolding in space near earth would allow you to make them larger and inspect them before they leave for venus.

Don't we want them to be rigid spheres?

Re: The Mars Helicopter Is Online and Getting Ready to Fly

#202

Post by cosmonaughty »

dragonwriter wrote: post #187
cosmonaughty wrote: post #186

Earlier quoted context omitted.

The link I posted points to a YouTube video of a vacuum chamber reduced to "Martian" pressure. It should have been obvious that my question was rhetorical, and that I provided the answer. Watch the YouTube video and compare it to the AVR cartoons that NASA is giving for millions of dollars per day.

Your post was sneering at the idea of it being real, and I generally don't click on video links without a clear idea of what they are (because video is a low-information-0er-time, high-emotional-engagement medium, and experience has proven that it's almost never worth doing) and I'm even less likely to do so with the implied content from the rest of your post.

Well then might I suggest a video on the official NASA web site? https://www.nasa.gov/feature/jpl/mars-virtual-reality-softwa... There are much better video specimens of science experiments on YouTube.

Re: The Mars Helicopter Is Online and Getting Ready to Fly

#203

Post by cosmonaughty »

shawnz wrote: post #87
laydn wrote: post #25

Why is nobody worried about the helicopter crashing to the rover and possibly destroying a science instrument? How far will the helicopter be from the rover?

The helicopter is itself also a science instrument. How do they prevent any of the instruments from destroying each other? Careful planning, I would guess

Not really a scientific instrument...more of a stage prop.

Re: The Mars Helicopter Is Online and Getting Ready to Fly

#204

Post by zhoujianfu »

ChuckMcM wrote: post #150
julienchastang wrote: post #93

Fun fact: This is not the first time a space program has flown on another planet. The Soviets launched weather balloons on Venus during the Venera missions [1] [1] https://en.wikipedia.org/wiki/Vega_program#Balloon

And given the density of Venus' atmosphere, here is a fun thought experiment. It may be possible to make 'titanium' balloons for longer term operation. The would work by creating the balloon envelope on earth, have a sealing mechanism that you activated in orbit so they had vacuum inside. And then drop them into the atmosphere. Same idea a glass floats on fishing nets[1] except with titanium (so they can withstand th…

Does anybody have any thoughts on how feasible it would be to make a metal “vacuum sphere” that floated in earth’s atmosphere?

That’d be pretty cool!

How huge would it have to be? Would it have to be made of titanium? Aluminum? Stainless steel?

How good are those materials at withstanding a vacuum (or partial vacuum) if the diameter was say... 50m?

I feel like at some size it must work, as the volume of air displaced goes up with r^3 and the surface area of metal only goes up with r^2.

If people here can do the math, maybe I could build one in time for next burning man...!

Re: The Mars Helicopter Is Online and Getting Ready to Fly

#205

Post by cpgxiii »

NikolaeVarius wrote: post #145
tal8d wrote: post #114

Earlier quoted context omitted.

Not in python, maybe. Smartbombs have been doing the necessary image processing with much less processing power, on much less capable sensors, for a long time.

What. I dont understand how you can make this claim. Guided bombs are NOT using CV with optical cameras. They use lasers, GPS, and other non "fancy" techniques. I just don't get in what world you think military munitions are using CV for targeting bombs.

The other poster mentions analog techniques used in contrast-tracking TV-guided munitions like the Walleye, but digital "CV-like" image/contour matching methods were used on the original Tomahawk cruise missile and the Pershing 2 missile to provide terrain-matching navigation and target guidance. GPS was neither sufficiently complete or accurate for strategic weapons in the late 1970s/early 1980s.

In more modern weapons, imaging IR sensors are well-established for terminal guidance on missiles like LRASM, JASSM, or NSM to distinguish targets from clutter and identify specific target features (specific parts of a ship, for example). Of course "traditional" "IR-homing" SAMs and AAMs now use imaging sensors (often with multiple modes like IR+UV) to distinguish between the target and decoys/jammers. Even your basic shoulder-fired anti-tank missile like Javelin requires some amount of CV to identify and track a moving target.

Re: The Mars Helicopter Is Online and Getting Ready to Fly

#206

Post by cpgxiii »

layoutIfNeeded wrote: post #9

>One of the most significant obstacles for landing on Mars will continue to present problems for our heroic helicopter now that it is safely on the surface. The atmospheric pressure on the surface of Mars is only about 1% that of Earth. To put that in perspective, the summit of Mount Everest has only one-third the atmospheric pressure of sea level. While this is thought to be at (or sadly in some cases beyond) the li…

It should be clear that while Eurocopter and Aerospatiale before them liked showing off specific modified helicopters in the Himalayas (up to and including landing on Everest), none of them were capable of carrying a useful payload to that altitude. Helicopter altitude records are much like zoom-climb records in jet aircraft - yes, you can reach those altitudes, but not for long and not while doing anything else.

Re: The Mars Helicopter Is Online and Getting Ready to Fly

#207

Post by tryauuum »

zhoujianfu wrote: post #204
ChuckMcM wrote: post #150

Earlier quoted context omitted.

And given the density of Venus' atmosphere, here is a fun thought experiment. It may be possible to make 'titanium' balloons for longer term operation. The would work by creating the balloon envelope on earth, have a sealing mechanism that you activated in orbit so they had vacuum inside. And then drop them into the atmosphere. Same idea a glass floats on fishing nets[1] except with titanium (so they can withstand th…

Does anybody have any thoughts on how feasible it would be to make a metal “vacuum sphere” that floated in earth’s atmosphere? That’d be pretty cool! How huge would it have to be? Would it have to be made of titanium? Aluminum? Stainless steel? How good are those materials at withstanding a vacuum (or partial vacuum) if the diameter was say... 50m? I feel like at some size it must work, as the volume of air displaced…

reminded me of a mythbusters episode where they created a lead balloon

Re: The Mars Helicopter Is Online and Getting Ready to Fly

#208

Post by dotancohen »

jojobas wrote: post #174
dotancohen wrote: post #136

Earlier quoted context omitted.

By many definitions the Earth-Moon system is a dual planetary system. The moon has more that 1% the mass of the Earth, which is by far the largest primary-secondary "not a planet" system in the solar system. Only not-a-planet Pluto and Charon exceed it. Also, Isaac Asimov considered the system a dual-planet system as the Moon's path around the sun is at no point convex nor retrograde.

Earth-Moon centre of mass is inside Earth, so, it's obvious that the Moon is orbiting the Earth, not both orbiting something else. 1% is an arbitrary threshold and solar orbit is dependent on external circumstances rather than the Earth-Moon system itself.

  > Earth-Moon centre of mass is inside Earth, so, it's
  > obvious that the Moon is orbiting the Earth, not both
  > orbiting something else.
I used to agree with that school of thought, until I came up with a small thought experiment. Consider two bodies that are right on the planet-moon / dual-planet definition threshold. Intuitively, increasing the orbital distance between them would push them in the direction of which definition: planet-moon or dual-planet?

I'd tend to say that separating them further would tend more towards planet-moon. Yet doing so moves the system's center of mass outside the larger body, so would actually push the system into the dual-planet definition by that criterion.

Re: The Mars Helicopter Is Online and Getting Ready to Fly

#209

Post by ChuckMcM »

minitoar wrote: post #185
simcop2387 wrote: post #181

Earlier quoted context omitted.

Weight and volume. The air has weight so it'll cost more to launch. The volume would also make them more difficult to launch. Assembling or unfolding in space near earth would allow you to make them larger and inspect them before they leave for venus.

I could see reusing an empty fuel tank or something as a cute way of doing this.

Oh I like that idea! Tricky to get it through the deceleration phase into the atmosphere but it would have a lot of volume. You would want some way to detach the engines (less mass) after you slowed down while still sealing the tanks.

Re: The Mars Helicopter Is Online and Getting Ready to Fly

#210

Post by bagels »

zhoujianfu wrote: post #204
ChuckMcM wrote: post #150

Earlier quoted context omitted.

And given the density of Venus' atmosphere, here is a fun thought experiment. It may be possible to make 'titanium' balloons for longer term operation. The would work by creating the balloon envelope on earth, have a sealing mechanism that you activated in orbit so they had vacuum inside. And then drop them into the atmosphere. Same idea a glass floats on fishing nets[1] except with titanium (so they can withstand th…

Does anybody have any thoughts on how feasible it would be to make a metal “vacuum sphere” that floated in earth’s atmosphere? That’d be pretty cool! How huge would it have to be? Would it have to be made of titanium? Aluminum? Stainless steel? How good are those materials at withstanding a vacuum (or partial vacuum) if the diameter was say... 50m? I feel like at some size it must work, as the volume of air displaced…

Vacuum would be pretty difficult. The strength requirements literally outweigh the buoyancy.
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