Nibb31

The problem is that any atmosphere that is thick enough to provide bouyancy is also thick enough to produce drag (and extreme heat) at hypersonic speed. You can't have both high-bouyancy and low-drag, and a Star Destroyer sized blimp is going to have massive drag.

Iridium has been bought back and is about to launch their next generation constellation. In fact, it's scheduled to launch next month on Falcon 9.

By definition, low population areas only cover a small population, which makes it a niche market. If there are any drawbacks to it (price, terminal size, capabilities, data limits, etc...) it will remain in the niche, just like Iridium. As long as we don't have that marketing data, it's impossible to predict whether it will succeed or fail. Musk has a tradition of disregarding marketing realities. He has his own reality distortion field. In some cases it works, in most others it doesn't. Neither Tesla, not SolarCity have ever reported any profits. SpaceX was profitable for the first time in 2015, but depending how much it gets sidetracked by Musk's Mars hobby, and the impact AMOS-6 had on the schedule, that might not repeat in 2016.

I think the terminals are going to need too much power for IoT applications, or even for pocket-sized mobile devices. Remember the closest sat will be 1000km away. I think it will be fixed subscriber boxes with something like a DVB-T antenna.

Who was talking about Dragon? I was speaking in general terms of what we should be focusing on. NASA should be focusing on goals that are achievable rather than pipe dreams that are based on budgets that will never materialize. The actual hardware should be designed around these goals instead of endlessly repurposing heritage stuff.

There is a lot more in your 20€/month subscription than just network infrastructure. You need more than just a network to run a service.

The Moon is much more affordable. I would like to see a small outpost on the rim of Shackleton crater.

Personally, I'd rather see us actually achieving something that is affordable and sustainable, rather than chasing dreams of Mars that will always be 30 years away.

Oh, and if all that wasn't enough, Dragon doesn't have EVA capability. It also relies on GPS for navigation and TDRSS for comms, which makes it incapable of going beyond LEO. Sure, you could add all that BEO capability, but it would require a redesign of pretty much every onboard system. You'd be better off starting from scratch.

You would need new terminal equipment, and yes it would probably need to be more powerful than your current phone. A typical 3G phone can talk to a radio tower several kilometers away. This will need to transmit to a satellite several hundred kilometers away.

I doubt that 50 million users pay 250€/year in France. A large number of them pay much less than that. In my household, we have 4 subscriptions. I pay 2€/month for the kids (Free Mobile no data). My wife and I pay 9€/month for unlimited calls and 3GB of data, which is more than enough for most people when you have wifi at home. So that's a total of 66€/year per person. Yes, telecom prices are exceptionally cheap here, but my point is specifically that in other countries, mobile operators have a huge margin to reduce pricing if they need to compete against satellite operators, and they will. You can't assume that constellation networks will replace mobile coverage everywhere. SpaceX is going to have to fight head-on against a very strong industry that is strongly implanted in strongly regulated national markets. As I said, they won't go down without a fight, and although it might end up turning a profit, I don't believe that the SpaceX constellation will be the cash cow that will pay for Mars colonies.

Why cheaper ? If the network costs $10 billion, it won't be cheap. In France, you can get 20GB 4G plans with unlimited text and phone for under 10€/month. That will be hard to beat. I'm not saying that sat communication doesn't have benefits. It all depends on how much people will be willing to pay for those benefits. If it ends up being cheaper, then existing operators will align pricing. They won't go down without a fight.

Of course. But you know that mobile networks are built using a heavy infrastructure of microwave and fiberoptic links. Next year, mobile operators are going to start deploying 5G. They won't let their huge investment in infrastructure go down the drain. If necessary, they will probably undercut anything SpaceX does by cutting prices. SpaceX will be left with the "rural" and "developing country" niches that are hard to monetize.

Of course, it lowers the unit cost of each individual bird, but that's rather pointless if the entire project costs an order of magnitude more than any other telecom project. The whole point of this constellation was originally to raise money for the Mars project, but even if it does become profitable, I don't see how it will bring in more billions than it will cost. In other words, if they are spending $10 billion with a super optimistic return on investment of $5 billion to fund Mars, then they might as well have just injected $10 billion into Mars. And this is all considering that the global telecom giants (AT&T, Verizon, Vodafone, etc...) are going to sit there with their massive investments in fiber and radio networks and watch Musk pick at their market share. Good luck with that.

They are building Boca Chica, Texas, which will give them a total of 4 launch sites (KSC, CCAFS, and Vandenberg), but Boca Chica is very constrained to low inclination (equatorial or GTO) launches. Not all launch sites can launch into any orbit, for example, KSC can only launch from something like 28° to 57° inclinations. The problem is that if you want global coverage from LEO, you need a polar orbit, which is only possible from Vandenberg. Low inclination launches are useless for this application.

Assuming that: All 50 satellites go the same inclination/orbital period SpaceX dumps paying commercial and government launch market to focus 100% on its own launches. Neither of which are realistic.

The actual dispenser might be patented, but I don't see that as an obstacle to dual-launching. As I said, it isn't really a market requirement, and launch providers adapt their offering to what their customers want to buy. It's more economical to design a smaller rocket for single payloads than to build a larger rocket for dual payloads that the market doesn't really want. Falcon 9 doesn't have the payload capability to deliver two typical comsats. It already struggles delivering one.

When designing a rocket, you typically design it for existing or planned payloads (notable exceptions are Falcon Heavy and SLS, which are both "rockets without a mission"). There is no point in building a rocket capable of sending 10 tons to GTO when most GTO comsats are in the 3 ton range. Ariane 5 was originally designed to launch the Hermes shuttle. The shuttle was cancelled, but the payload mass requirements were maintained, so it ended up being too large and too expensive for commercial launches, which make up the bulk of its manifest. So they came up with the dual launch capacity as a way to overcome the launcher's market overcapacity. This has a serious drawback in terms of flexibility. The payloads must both be targetted at a similar longitude (this is only used for GTO launches) and must follow the same launch schedule. If a payload from one customer is delayed, then the other customer is also delayed, which has a huge impact on revenue generated from the satellite. For those reasons, most customers prefer a single launch rather than dual launch, which is why Ariane 6 will be designed with a lighter 2 booster configuration for commercial launches and a 4 booster configuration for some rare heavier payloads.

I meant DreamChaser, which is a spaceplane. The rear section is disposable and carries unpressurized pallets externally and solar panels, which makes it comparable to Dragon's trunk.

Sorry, DreamChaser.

No engines. No tanks. The Dragon trunk is just a hollow cylinder that serves as a mounting point for the solar panels, as a radiator, and as a shroud for unpressurized cargo. (am I repeating myself ?) It's smart if you can carry the service module back with you, which is basically what Dragon does. Of course, bringing everything back with you carries a penalty in terms of heatshield and landing equipment mass. The cargo version of DreamChaser will not have a trunk, but the aft section will be disposable, and will carry the docking port, solar panels, and unpressurized cargo pallets.

A service module typically contains tanks and engines, as well as other equipment. The Dragon trunk is just a hollow cylinder that serves as a mounting point for the solar panels, as a radiator, and as a shroud for unpressurized cargo.

Kerbart is right. Your profile might be more suited to QA testing than actual programming. You might want to look at getting some education in Software Quality.

The physical properties of materials are what determine a theoretical speed limit. As I said above, the fastest scramjet ever built was the X-43.

The record for a jet aircraft is 123 500 ft on a modified Mig-25. An F-104 reached 120 000 ft. I wouldn't call that "flight" really, because reaching those altitudes is basically just flinging the aircraft as high as possible. The U-2 could do steady flight at 70000 ft and the SR-71 flew up to 85000 ft at 3500km/h, which is pretty much a record for unassisted level flight. The scramjet-powered X-43 reached Mach 10 at 98000 ft, but needed a Pegasus rocket to reach Mach 7.