Moon Cam

[dlorde]

Presently, the best use for such a device would be to land it right next to one of the Apollo landing sights. But I can't see spending that much money just to prove wrong a few morons who will claim that the whole thing is just part of the conspiracy anyway. Although, I don't doubt that such a venture will one day be inexpensive enough that, probably sooner than we think, some private company will send robots to explore the Apollo landing sites.

ISTR a sci-fi story where the Apollo landing sites were protected and preserved for posterity as the 'First Places Man Set Foot Beyond His Own Planet', or something. Sounded like a good idea to me - those footprints will last pretty much forever unless some prat in a sports buggy starts a long distance 'Round The LEMs' race...

 

[Varanid]

IANAA(stronaught) and correct me if I am wrong, but isn't there a big jump in the level of shenanigans necessary to reach the moon relative to reaching LEO? If I understand correctly, we can send stuff into LEO relatively "easily" and "cheaply". However, chucking something all the way to the moon requires some elbow grease.

Then, actually landing (carefully) on the moon?

Point being, while I will gladly watch the "earth channel" as seen from the moon, I doubt it is economically feasible anytime soon.

 

[HopDavid]

IANAA(stronaught) and correct me if I am wrong, but isn't there a big jump in the level of shenanigans necessary to reach the moon relative to reaching LEO? If I understand correctly, we can send stuff into LEO relatively "easily" and "cheaply". However, chucking something all the way to the moon requires some elbow grease.

Then, actually landing (carefully) on the moon?

Point being, while I will gladly watch the "earth channel" as seen from the moon, I doubt it is economically feasible anytime soon.

The metric commonly used is delta V, change in velocity. Usually measured in kilometers/second.

Earth to LEO: 9 to 10 km/s.
Earth to GEO: 13 to 14 km/s.
Earth to moon soft landing: 15 to 16 km/s.

The first impulse when comparing 10 km/s to 14 km/s is to think "That's only a 40% increase."

But need for propellant doesn't scale linearly with delta V, rather exponentially.
(mass propellant+dry mass)/(dry mass) = e^{(delta V/Vexhaust)}
One of the better chemical bipropellants is oxygen and hydrogen. Exhaust velocity is about 4.4 km/s.

e^(3/4.4) = about 2.

So each 3 km/sec added to the delta V budget is like a square on this chess board:

At first glance it may seem that vast amounts of propellant are the obstacle. Not so. Propellant is a small fraction of the vehicle expense.

A certain fraction of the vehicle must be rocket engines, fuel tanks, structure, etc. Once the delta V climbs so high that mass fraction becomes undoably small. To get around this we use expendable stages. Expendable is another word for disposable. If we threw away a 747 after each transcontinental trip, no one could afford plane tickets.

 

[Roboramma]

You're right.

Sometimes I'm an irritable old curmudgeon quick to assume someone's yanking my chain.

I owe Madalch an apology.

Thanks for that, and also for your contributions to this thread, it's very interesting to a space enthusiast like me.

 

[Blue Mountain]

A serious problem I'd have with the mooncam is it would be impossible to tell its output apart from a well programmed computer simulation. Especially when you count the cost of building a real camera capable of surviving the moon's temperature fluctuations and then getting it there versus writing a good computer program. You can write some really neat software for a couple million dollars.

 

[falkowsi]

"How do you grow pineapples under the ocean?"

Ask Spongebob.

 

[HopDavid]

A serious problem I'd have with the mooncam is it would be impossible to tell its output apart from a well programmed computer simulation. Especially when you count the cost of building a real camera capable of surviving the moon's temperature fluctuations and then getting it there versus writing a good computer program. You can write some really neat software for a couple million dollars.

A static cam would not draw my interest.

Binocular cams (for 3-D) on a rover? That's a different story. The urge to see what's over the next hill and behind that rock is more compelling. A moon rover could enjoy higher bandwidth and shorter light lag than the Martian rovers spirit and opportunity.

A proposed mission I was very excited about was Lunar Polar Volatiles Explorer. It was designed to study the possible ice sheets detected by Chandrayaan-1. However it didn't make it to the Decadal Survey recommendations . This rover was going to cost between 800 million and 1.1 billion dollars depending on whether it was solar/battery or whether it was nuclear powered. The nuclear powered version was expected to have a longer life span.

Can a Lunar rover be landed for less? It seems these teams think so. One team I'm particularly excited about is Moon Express. They've managed to design a more compact range finding radar and are working on software for an autonomous lander. An autonomous lander that works well would not only be a game changer for lunar exploration, but for NEO exploration as well.

 

[falkowsi]

Binocular cams (for 3-D) on a rover? That's a different story. The urge to see what's over the next hill and behind that rock is more compelling.

Another hill and another rock ? While a rover would be more interesting, it would also be a lot more expensive and complicated. A rover could get itself stuck for instance. Sending the images back to earth would also be more difficult from a moving platform.

 

[HopDavid]

Ask Spongebob.

I hadn't thought of that.

Plankton is my hero. U is for Uranium!

 

[HopDavid]

Another hill and another rock ? While a rover would be more interesting, it would also be a lot more expensive and complicated. A rover could get itself stuck for instance. Sending the images back to earth would also be more difficult from a moving platform.

Communication is doable as been demonstrated by the Mars Rovers.

Is it too difficult to do within reasonable budgets? Again, I will point to the Google Lunar X Prize:

"The Google Lunar X PRIZE is igniting a new era of lunar exploration by offering the largest international incentive prize of all time. A total of $30 million in prizes are available to the first privately funded teams to safely land a robot on the surface of the Moon and have that robot travel 500 meters over the lunar surface and send images and data back to the Earth. Teams must be at least 90% privately funded, though commercially reasonable sales to government customers are allowed without limit."

I would give better than even odds the prize will be won by one of these teams.

 

[falkowsi]

Communication is doable as been demonstrated by the Mars Rovers.

The Mars rovers had a fairly low data rate. Good enough for still pictures, but not really for a webcam. Relaying the signals through an orbiter is tricky because the moon's gravity field is too irregular to allow stable orbits.

The number of people that would pay for the webcam feed would probably not be enough to fund the mission, or at least not for very long.

 

[HopDavid]

The Mars rovers had a fairly low data rate. Good enough for still pictures, but not really for a webcam. Relaying the signals through an orbiter is tricky because the moon's gravity field is too irregular to allow stable orbits.

The number of people that would pay for the webcam feed would probably not be enough to fund the mission, or at least not for very long.

Signal strength goes with inverse square of distance. Weak signals fall to high signal to noise ratio. So bandwidth is also affected by inverse square. Thus high lunar bandwidth is much more doable than high Martian bandwidth.

The Lunar Reconnaissance Orbiter achieved 100Mbps.