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Pseudo-satellites: A cheap alternative to satellites is starting to take off

economist.com

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Re: Pseudo-satellites: A cheap alternative to satellites is starting to take off

#31

Post by pavel_lishin »

trhway wrote: post #30

one of the things that really can be resolved by technology here is re-fueling in air. You don't need solar panels and batteries if your drone hanging at 20km can be automatically supplied by refueling missions of another drone. Say 40kg of batteries would contain 14KWh, ie. equivalent of 1.5 liter of gas or with adjustment for the thermodynamic efficiency of a gas turbine - 4 liter. Thus 30kg (lets allocate 10kg for…

But if you can build a drone that can stay up nearly indefinitely, why bother refueling it?

Would it make more sense to perpetually spend money on fuel (and the fuel it takes to launch the fuel), or to spend more money up front to design a robust HARP that only comes down in case of severe fault, and is cheap enough that it's easier to just replace it?

Re: Pseudo-satellites: A cheap alternative to satellites is starting to take off

#33

Post by damian2000 »

electromagnetic wrote: post #11

I wonder what the lower weight limit is on these. The solar panels produce 1kw/kg the batteries store 350 watts per kg. The whole thing weighs 50kg and has a 23m wingspan. Training gliders weigh about 600kg, and they have a 41kw gas engine to self propel and have a wingspan of 18m (based on the one linked on the wikipedia article). Average weight is about 80kg for a male. So these can likely get 160-200kg airborne wi…

I agree, but hundreds of nuclear power sources hovering around the planet controlled by a single corporation ... sounds like the plot of a James Bond movie.

Re: Pseudo-satellites: A cheap alternative to satellites is starting to take off

#34

Post by rwallace »

nothiggs wrote: post #18

As for using it for military purposes - wouldn't any country it flies over that has the ability to detect it, just shoot it down?

If your enemy is a national government, yes. But we're at the stage now where national governments should know better than to get into fights with each other. Unless the recent idiocy between America and Russia gets out of hand, likely enemies in the near future are nonstate actors like ISIS who would have difficulty shooting down something at that altitude.

Re: Pseudo-satellites: A cheap alternative to satellites is starting to take off

#36

Post by ericd »

privong wrote: post #3
nlkndlk wrote: post #2

>That Arianespace, a French rival of SpaceX, announced on the same day that two satellites it had tried to launch to join the European Space Agency’s Galileo constellation (intended to rival America’s Global Positioning System), had entered a “non-nominal injection orbit”—in other words, gone wrong—shows just how difficult the commercialisation of space can be. >If spacecraft are so precarious, then perhaps investors…

> It is absolutely disgusting to suggest that, after we gutted NASA in order to make opportunities for private enterprise, we should just stop sending stuff to space altogether. I do not think that was the point of the article. Some things do not absolutely need to be beyond the atmosphere, they only need to be up high. In the past, the technology to keep things at what might be termed "moderate" altitudes has not be…

He may have a point - it's locally optimal to decrease the cost of applications, but it may be globally optimal to pay more for those applications to increase space launch volume and decrease the marginal cost of a launch.

Re: Pseudo-satellites: A cheap alternative to satellites is starting to take off

#37

Post by seanflyon »

dmd wrote: post #22
seanflyon wrote: post #20

Earlier quoted context omitted.

At 70,000 feet it would be expensive to shoot down and quite possibly difficult to detect.

Why would it be expensive to shoot down? Just send another one of these up after it, and crash into it. Why would it be difficult to detect? It's fairly hard to hide when your entire purpose is to transmit a signal.

> Just send another one of these up after it

I'm not sure if these move fast enough to chase each other down; I bet it takes a while to get up to elevation. Even if that works it's still the same cost to shoot down as it is to replace.

Re: Pseudo-satellites: A cheap alternative to satellites is starting to take off

#38

Post by th0br0 »

TeMPOraL wrote: post #25
tsotha wrote: post #21

Earlier quoted context omitted.

>Increasingly, it's people like Elon Musk, Sergey Brin, et al. - ones with enough resources to liberate themselves from the yoke of the greedy algorithm our economy is... Eh, what? SpaceX is profitable. And you can't get away from basing your space program on the economy, either because it determines your tax base or (potentially) because companies do space things for profit.

Let me clarify what I meant. Sure, SpaceX is profitable. It has to be. But Elon right now seems to be using the economy to pursue his own goals with Tesla and SpaceX, but those goals are not dictated by what is profitable. He had to amass some capital and then basically force the economy to accept his visions. Tesla Motors pretty much created the market for electric cars that don't suck. SpaceX and Tesla were not eco…

Wonderful comparisons; I might have to steal them from you at some point. Thanks!

Re: Pseudo-satellites: A cheap alternative to satellites is starting to take off

#39

Post by electromagnetic »

damian2000 wrote: post #33
electromagnetic wrote: post #11

I wonder what the lower weight limit is on these. The solar panels produce 1kw/kg the batteries store 350 watts per kg. The whole thing weighs 50kg and has a 23m wingspan. Training gliders weigh about 600kg, and they have a 41kw gas engine to self propel and have a wingspan of 18m (based on the one linked on the wikipedia article). Average weight is about 80kg for a male. So these can likely get 160-200kg airborne wi…

I agree, but hundreds of nuclear power sources hovering around the planet controlled by a single corporation ... sounds like the plot of a James Bond movie.

It definitely does! However, if one of these did go uncontrolled and break up, it's a kinetic impactor. The Uranium core should act like a DU penetrator if the craft disintegrated, meaning it should penetrate ~6 times its length.

The New Horizons craft had the largest space based RTG at about 50kg. The dimensions roughly 0.5m in diameter and over 1.1m long. This means it would end up roughly 6.6m underground, or about 20ft deep. As long as the craft are kept above abandoned land, I honestly don't see a problem with it.

As far as I see they'll be an inevitable choice in areas above 40 degrees latitude. If winter nights are too long to recharge batteries they'll never happen in those areas. I mean by their current proposal the whole UK is out of their market as well as Canada, Alaska and all of northern Europe.

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