People make too much of the 4400 satellite number of CommX.SpaceX can generate a large % of CommX revenue with less than 10% of the constellation in operation.The goal of so many satellites is to provide services even for customers that have quite a restricted view of the sky (urban canyons), and ultra high bandwidth on the full system.If they start without catering to such customers, they can make due with a few hundred satellites and generate billions USD/yr in revenue.The balance of satellites can wait until ITS/mini ITS/Raptor F9 is operating.The best customers for CommX are those that must choose between unreliable internet, slow internet or ultra high latency internet. CommX delivers reliable/fast/mobile/low latency, but can charge a substantial premium in return. Competing in urban canyon scenarios are the low profitability situation where you must go against the big fiber telcos.GEO dedicated satellite links cost over 20x as much as land line links with huge latency. SpaceX can win over that entire market with moderately lower costs.CommX has a lot more market potential outside mainland USA and Europe, several times more market. In places where there's no fiber or there's a single fiber cable that's fails nearly every month.It makes zero sense to launch the entire constellation with Gen I satellites. It makes far more sense to operate a reduced Gen I constellation, roll out a fuller constellation with Gen IIs and only roll out the full thing with Gen III satellites. By the time Gen IIIs are ready to roll, ITS or mini ITS is flying.
Space X themselves have said 800 to start the constellation up, that's 20% of the final number, not 10%.
And add second thought: they barely can change anything in second stage. So this leaves idea of something similar to "reusability kit" - except no engines, no landing legs, just TPS, some weight to adjust CoG and parachutes. This "kit" can be heavy on this particular flight, as it's only test and there is no real payload. If it's mounted as payload, but never separated it doesn't invalidate this flight as qualification flight. And since it's adding some experimental stuff attached as payload it fits description of "hail mary". If result of this test is promising then later they can work on integrating this stuff into S2.
Musk wants to make Falcon rockets fully reusablehttps://spaceflightnow.com/2017/04/11/musk-wants-to-make-falcon-9-rocket-fully-reusable/
One thought. This comes close after successful experiment with bringing back fairing. And fairing probably doesn't have any complicated solutions for reusability. And add second thought: they barely can change anything in second stage. So this leaves idea of something similar to "reusability kit" - except no engines, no landing legs, just TPS, some weight to adjust CoG and parachutes. This "kit" can be heavy on this particular flight, as it's only test and there is no real payload. If it's mounted as payload, but never separated it doesn't invalidate this flight as qualification flight. And since it's adding some experimental stuff attached as payload it fits description of "hail mary". If result of this test is promising then later they can work on integrating this stuff into S2.
What SpaceX does could be better characterized as R&D. I build astronomical instruments to do science. The distinction is that tons of research goes into how to implement various 'features' of the instrument -- each of these research projects is jokingly called a 'science project' -- but really they are engineering or technical evaluations, thus R&D. Once the instrument is built, tested, and integrated at an observatory, science begins.
Quote from: Radical_Ignorant on 04/11/2017 06:00 pmOne thought. This comes close after successful experiment with bringing back fairing. And fairing probably doesn't have any complicated solutions for reusability. And add second thought: they barely can change anything in second stage. So this leaves idea of something similar to "reusability kit" - except no engines, no landing legs, just TPS, some weight to adjust CoG and parachutes. This "kit" can be heavy on this particular flight, as it's only test and there is no real payload. If it's mounted as payload, but never separated it doesn't invalidate this flight as qualification flight. And since it's adding some experimental stuff attached as payload it fits description of "hail mary". If result of this test is promising then later they can work on integrating this stuff into S2.I like the KISS approach for 2nd stage reusability. Seems possible that a nose mounted heat shield and some nose weight could be ready to go for this flight. Don't even really need a parachute. Just good telemetry showing how things worked out.
So does 2nd stage reusability include water landing? Or does a desire to avoid seawater corrosion firmly require landing on dry terra firma?
Quote from: Radical_Ignorant on 04/11/2017 06:00 pmAnd add second thought: they barely can change anything in second stage. So this leaves idea of something similar to "reusability kit" - except no engines, no landing legs, just TPS, some weight to adjust CoG and parachutes. This "kit" can be heavy on this particular flight, as it's only test and there is no real payload. If it's mounted as payload, but never separated it doesn't invalidate this flight as qualification flight. And since it's adding some experimental stuff attached as payload it fits description of "hail mary". If result of this test is promising then later they can work on integrating this stuff into S2.So does 2nd stage reusability include water landing? Or does a desire to avoid seawater corrosion firmly require landing on dry terra firma?If landing on dry land is required, then can that be done with chutes, or would it require powered thrust?
Quote from: AncientU on 04/11/2017 10:26 amWhat SpaceX does could be better characterized as R&D. I build astronomical instruments to do science. The distinction is that tons of research goes into how to implement various 'features' of the instrument -- each of these research projects is jokingly called a 'science project' -- but really they are engineering or technical evaluations, thus R&D. Once the instrument is built, tested, and integrated at an observatory, science begins.If you build something directly from the equations in a design handbook or ASME standards and delivers adequate, predicted performance it's engineering.If the design equations in the open literature don't give you the performance you need.If you're simulations don't match the recorded flight data or do so with so much uncertainty they are practically useless.If you can't put a model in a wind tunnel because no wind tunnel exists that comes anywhere close to matching the conditions you need to model.If you have to do curve fitting, dimensional analysis on the equations and restructure your CFD to get a model that matches the real world. That's science.
I firmly believe it will be powered landing on land or ASDS. I have some doubt that deorbit with the main engine can provide the needed precision with startup and wind down instabilities. So they need smaller engines. The next step, making the engines strong enough for landing and providing the fuel, won't make it that much more complex. The harder part is getting it through reentry without breaking up, heatshield and aerosurfaces, protection for the engine, if not the engine bell extension.The first attempt with the FH maiden flight may not have the landing engines and propellant. It may just be a water landing with the lowest speed attainable with the main engine. It would demonstrate the harder part, the reentry and with some luck (plus maybe a floating device) ability to recover the wreckage.I see the second stage closer to the first stage than to the fairing.
All at sea about reusabilitySpaceX is talking about not only increasing their flight rates, but attempting to recover the Falcon 9 payload fairing and second stage as well. Dick Eagleson examines how efforts to prove out second stage and payload fairing recovery might proceed and looks at related logistic challenges for SpaceX as it moves to greatly increase its launch cadence.Monday, April 10, 2017
Would SpaceX's pad failure count as science? They (presumably) created novel states of matter outside a lab, after all.
Wrong takeaway and summary. It isn't science, it is an engineering. It was just a standard engineering trade within established ground rules. Nothing new was discovered. The control surfaces were required because Spacex uses low impulse GN2 thrusters (a ground rule). Using higher performance thrusters (hyper or RP-1/GOX) would negate the need for control surfaces. It was a complexity trade.
MVac's are static tested w/o the nozzle, so maybe. Probably not, rockets aren't LEGO elements.Edit/Lar: fixed pet peeve.
However, I deleted it after it occurred to me that S2 delivering to LEO doesn't have to do a reentry burn immediately after releasing the payload; it could stay in orbit as long as it needed to in order to get the alignment needed to return to the launch site or other convenient location. For GTO, if I'm not mistaken (correct me if I'm wrong) the orbit they're generally on intersects the Earth, but they could raise it without huge dV requirements.