For Questions That Don't Merit Their Own Thread

[Nuke]

21 hours ago, K^2 said:

As someone who once flew a DJI drone into a wing of a foam-body RC plane, can sort of confirm.  (I know that's technically all very different scenarios.)

id say that the drone control systems are so stronk that this is very unlikely. especially if you have a set coordinate system, say with a few tracking dots on the rover. drone control is so good they use swarms for displays during things like firework shows. 

but now that i think about it, just put a brushless motor in the center of the panel cluster, with an arm attached with some kind of wiper or brush. just give it a spin every now and again. the whole system could come in under a few grams. 

Edited January 21, 2023 by Nuke

[K^2]

1 hour ago, Nuke said:

id say that the drone control systems are so stronk that this is very unlikely. especially if you have a set coordinate system, say with a few tracking dots on the rover. drone control is so good they use swarms for displays during things like firework shows.

Mars has strong winds with very sudden gusts - low pressure means that wind speed variations take longer to dissipate, and harsh day/night cycle changes generate a lot of pressure gradients. The response to air shifting can only be so rapid. That isn't just a matter of precise measurement, but you are inherently limited by aerodynamics in how fast you can respond and correct your position. Anything close enough for the blade wash to start clearing sand is also a collision hazard.

I'm sure it might be a warranted risk in some situations, but it's not something that would likely be attempted if it can at all be avoided.

[kerbiloid]

When they start seriously exploring Mars, they will anyway need a marsocopter drone with attached broom - to broom the dust from Martian civilisation and visitors' artifacts.

Spoiler

Thus, it will just have a button "Pad brooming" mode.

Also useful for unexpected landing at custom place.

[kerbiloid]

It took 200k years.

https://www.youtube.com/@primitivetechnology9550/videos

[steve9728]

Today I drove our family to another city in my dad's car. I saw the dog killed by car on the highway first time which has the speed limit of 120km/h. As a rookie driver who hasn't driven more than 5000 km, I have a question: what would be the best way to deal with this situation where I was about to run a dog over on the highway?

[Gargamel]

1 hour ago, steve9728 said:

Today I drove our family to another city in my dad's car. I saw the dog killed by car on the highway first time which has the speed limit of 120km/h. As a rookie driver who hasn't driven more than 5000 km, I have a question: what would be the best way to deal with this situation where I was about to run a dog over on the highway?

If you can safely avoid hitting a small animal like a dog without causing a wreck with other cars, then do so.      But if the attempt to avoid the animal will cause you to hit another car or get hit yourself, then sorry doggy, you’re getting run over.    
 

.That’s a small animal.  I don’t know about your local, but some places have big animals.    Deer, moose, bear, camel, kangaroo, elephant, etc.   Those animals can easily kill people in a vehicle if they are hit at highway speed.    So in this case, let’s hope the people behind you are also paying attention when you slam on the brakes.    
 

Small animal: try not to hit, but it’s acceptable to do so if no other choice.    Big animal: Do your best to not hit these at speed.    200kg of meat entering the passenger compartment at 100kph is usually far worse than getting rear ended.   

[steve9728]

58 minutes ago, Gargamel said:

That’s a small animal.  I don’t know about your local, but some places have big animals.    Deer, moose, bear, camel, kangaroo, elephant, etc.   Those animals can easily kill people in a vehicle if they are hit at highway speed.    So in this case, let’s hope the people behind you are also paying attention when you slam on the brakes.

There're two kinds of highway in China, one is the 'Expressway', and one is the 'National Highway'. The good news is those big animals is really ‘rare' to hit in the expressway in China because there are many parts of those where viaducts will be built to take straight lines as possible. But the national highway... well, my stereotypical national highway is "don't be too surprised at what you hit." And one of my father's friends bragged at a gathering days ago that he almost hit a yak on the national highway in Tibet.

Guess the dog got ran over I saw was the farmer's dog near the highway. Lesson I learn this time is drive more carefully and more decisive at same time

Of course, there will something unexpected. This includes, but isn't limited to, the lorries taking pigs to the abattoir with their doors didn't lock completely, resulting in pigs running on the expressway almost once or twice a year.

Edited January 23, 2023 by steve9728

[JoeSchmuckatelli]

6 hours ago, steve9728 said:

situation where I was about to run a dog over on the highway

 

5 hours ago, Gargamel said:

Small animal: try not to hit, but it’s acceptable to do so if no other choice.    Big animal: Do your best to not hit these at speed.    200kg of meat entering the passenger compartment at 100kph is usually far worse than getting rear ended

This is really good advice - don't kill yourself or anyone else trying to save the dog.  Brake hard and hold your lane (if necessary) but any high speed evasive turning can result in a flip or worse accident.  Bye doggy is better than bye Dad! 

I had a near accident in Canada - flying around mountain roads when I came around a turn to find a herd of cattle being driven up the road filling both lanes. 

Stood on the break pedal and only at the last instant eased my truck into the oncoming lane to avoid a cow. Came to a halt with cattle on 3 sides of my truck.  Would have killed me and the cow. 

Rancher merely waved and kept driving the herd. 

You do what you can - but don't make a situation worse by panicking! 

[TheSaint]

When I was young. And dumb. One of the first accidents I was ever involved in I swerved to avoid a squirrel. There was ice on the road, spun out, ended up hitting the curb sideways at about 30 MPH. Minor damage, but the car was undrivable, had to be towed. Cop happened on the scene while the tow driver was hooking me up. When everything was explained to him, his only comment was, "You know, squirrels are not an endangered species."

So, yeah, what they said. If the animal isn't big enough to injure you, don't let it cause a crash. It sucks, but that's just how it is.

Edited January 23, 2023 by TheSaint

[kerbiloid]

A moose and squirrel rebel alliance.

A squirrel runs on the road, the driver turns the wheel, and the car gets into a moose in ambush.

[TheSaint]

1 hour ago, kerbiloid said:

A moose and squirrel rebel alliance.

[monophonic]

15 hours ago, Gargamel said:

If you can safely avoid hitting a small animal like a dog without causing a wreck with other cars, then do so.      But if the attempt to avoid the animal will cause you to hit another car or get hit yourself, then sorry doggy, you’re getting run over.    

.That’s a small animal.  I don’t know about your local, but some places have big animals.    Deer, moose, bear, camel, kangaroo, elephant, etc.   Those animals can easily kill people in a vehicle if they are hit at highway speed.    So in this case, let’s hope the people behind you are also paying attention when you slam on the brakes.    

Small animal: try not to hit, but it’s acceptable to do so if no other choice.    Big animal: Do your best to not hit these at speed.    200kg of meat entering the passenger compartment at 100kph is usually far worse than getting rear ended.   

 

10 hours ago, JoeSchmuckatelli said:

This is really good advice - don't kill yourself or anyone else trying to save the dog.  Brake hard and hold your lane (if necessary) but any high speed evasive turning can result in a flip or worse accident.  Bye doggy is better than bye Dad! 

<snip>

You do what you can - but don't make a situation worse by panicking! 

Very good advice there. To add, if you see a big animal e.g. elk crossing the road ahead you, slow down immediately. They travel in groups and chances are rest of the family will follow shortly. If you cannot help hitting the animal, try to aim for the rump. Not only is that side where the animal is making room for you to evade but any antlers are at the other end of it. Those can - and have - pierced windshields like armour piercing shot and cause even fatal injuries in otherwise survivable accidents. Unfortunately hooves exist on both ends of the animal. If the ditch is clear of rocks and trees it may be safer to go there than hit a big animal.

[mikegarrison]

I just saw a study from the University of Washington that says that the most deadly animal in North America is the deer. This is primarily due to fatal (to humans) car/deer collisions.

When I was a kid, I was in a car that hit a deer. Only fatality that time was the deer, although the car also did not come out very well.

[kerbiloid]

3 hours ago, monophonic said:

if you see a big animal e.g. elk crossing the road ahead you, slow down immediately.

+1

Spoiler

 

 

3 hours ago, mikegarrison said:

University of Washington that says that the most deadly animal in North America is the deer.

Spoiler

Yes. The arthropod deer. It's a documentary.

[K^2]

13 hours ago, mikegarrison said:

When I was a kid, I was in a car that hit a deer. Only fatality that time was the deer, although the car also did not come out very well.

I knew a guy whose car got hit by a deer. As in, he was just driving on the highway, and his car got t-boned by a deer that jumped out from the forest. The passenger door got a huge dent and was permanently jammed. The deer ran away back into the forest. The most comical part was that the car was a Geo Metro, and so it getting hit by the deer instead of the other way around just makes sense somehow.

[mikegarrison]

1 hour ago, K^2 said:

I knew a guy whose car got hit by a deer. As in, he was just driving on the highway, and his car got t-boned by a deer that jumped out from the forest. The passenger door got a huge dent and was permanently jammed. The deer ran away back into the forest. The most comical part was that the car was a Geo Metro, and so it getting hit by the deer instead of the other way around just makes sense somehow.

There was an incident in my family where our car was damaged while my mother was driving it, and she swears a large dog smashed into the car and then ran off. She also says a bystander told her "he does that all the time".

[Gargamel]

About 4 years ago I was working a really funky shift, 4pm-2am.   I worked in the suburbs and lived on a farm, so my commute would take my through the rural areas at night when the deer were most active on a country ‘highway’ doing about 70mph.  
 

Over the course of about 10 months I hit one deer with a minor abrasion to the headlight, was hit by two deer on different occasions, leaving small dents in both rear quarter panels, and ran over one snapping turtle.   That one took my bumper clean off and cosmetic damage to the undercarriage as I went over him.    I got of out the car, stared to walk I’ve to him, he spun around, hissed loudly at me and sprinted off into the trees.   I’m lucky I got him square on, if I had hit him with a tire I might of flipped the car.  

8 hours ago, mikegarrison said:

There was an incident in my family where our car was damaged while my mother was driving it, and she swears a large dog smashed into the car and then ran off. She also says a bystander told her "he does that all the time".

My old German shepherd hated school buses.   She broke her line once and was able to catch it and started attacking the tire.  

[sevenperforce]

On 1/24/2023 at 5:51 PM, mikegarrison said:

On 1/24/2023 at 4:13 PM, K^2 said:

I knew a guy whose car got hit by a deer. As in, he was just driving on the highway, and his car got t-boned by a deer that jumped out from the forest. The passenger door got a huge dent and was permanently jammed. The deer ran away back into the forest. The most comical part was that the car was a Geo Metro, and so it getting hit by the deer instead of the other way around just makes sense somehow.

There was an incident in my family where our car was damaged while my mother was driving it, and she swears a large dog smashed into the car and then ran off. She also says a bystander told her "he does that all the time".

The first time I ever had my kids in my new SUV, a bunch of deer were crossing the road so I slammed on the brakes. Came to a full stop just before I would have hit one. And then another one ran straight into the side of my car at full tilt.

[StrandedonEarth]

How much dV is needed to go from GEO (GSO) to lunar impact? Looking at the subway maps, it takes more dV to circularize in GEO from LEO than it does for a lunar intercept, but it doesn't list GEO-to-intercept. Just curious as to how much more it would take to move junk from the GEO 'graveyard' belt to a lunar intercept, so the scrap could be collected from the surface. I know it would probably be too widely scattered to be worthwhile; just spitballin' here. Probably easier to collect the stuff from the graveyard belt for salvage directly (I know there's little point to that at this time). I know there's practically infinite room there, but that's what they thought about LEO at first too. Given a few hundred years of GEO launches, it may start to feel crowded...

Edited February 3, 2023 by StrandedonEarth

[kerbiloid]

Spoiler

0.68 +0.14 + 0.68 + 1.72 = 3.22 km/s

GSO circularization = 1.42 km/s

[StrandedonEarth]

1 hour ago, kerbiloid said:

  Hide contents

0.68 +0.14 + 0.68 + 1.72 = 3.22 km/s

GSO circularization = 1.42 km/s

Thanks, that's a better dV map than the one I looked at. But I only asked for impact, and since it's 0.68km/s from GTO to lunar intercept, it would be less than that for GSO to intercept. Just not sure how much less. I guess I could figure it out with RSS...

Edited February 3, 2023 by StrandedonEarth

[sevenperforce]

On 2/3/2023 at 3:42 PM, StrandedonEarth said:

I only asked for impact, and since it's 0.68km/s from GTO to lunar intercept, it would be less than that for GSO to intercept. Just not sure how much less.

No, it would be considerably more. Oberth is your friend.

I haven't done the math, but it might actually be more efficient to burn from GSO to GTO and then burn from GTO to intercept.

[LHACK4142]

On 1/17/2023 at 2:38 PM, LHACK4142 said:

What's the name of the low-pitched droning aoaowowoaowoaowoaao-ish sound that some planes, especially military ones, make?

I found out that it's the aim-9 sidewinder.

 

[Gargamel]

Well, that’s not the plane, that’s an artificial  tone indicating the seeker head is searching.  Glad you found your answer though.   

[sevenperforce]

16 hours ago, sevenperforce said:

On 2/3/2023 at 3:42 PM, StrandedonEarth said:

I only asked for impact, and since it's 0.68km/s from GTO to lunar intercept, it would be less than that for GSO to intercept. Just not sure how much less.

No, it would be considerably more. Oberth is your friend.

I haven't done the math, but it might actually be more efficient to burn from GSO to GTO and then burn from GTO to intercept.

I just did the math, and while an Oberth gate maneuver (burning down into an eccentric orbit and then burning again at perigee to raise) isn't indicated, the burn you need is still pretty significant. In GEO, you're circling Earth at just under 3.1 km/s; you'll need to add another 1.05 km/s to raise your apogee to 384,000 km for a lunar intercept trajectory.

Granted, that's less than the 1.5 km/s disposal burn you'd need to do to lower your perigee into Earth's atmosphere. But still much more than end-of-life comsats have in their tanks.