Quote from: IRobot on 12/22/2015 09:12 amQuote from: edkyle99 on 12/22/2015 05:38 amNow that a stage has landed, the real work begins. There is still a long way between this experimental landing and the ideal of saving money by reusing stages. So far, reuse is adding to SpaceX costs. - Ed KyleAs all R&D projects... first you spend, then you take benefits.And in fact this is not completely true. One of the biggest benefits for now will not be stage reusing. It will be the learning from used stages. Checking structural components would be one of the most important areas for future improvement. Let's say they had pulled this off in April, on a barge landing. And after the flight they could have seen that the helium tank support structure was not in good conditions, thus preventing the later failure.also, don't forget stock value. I'd bet the increase in the stock value after such a successful night is more than sufficient to cover up the extra costs of the landing of tonight.
Quote from: edkyle99 on 12/22/2015 05:38 amNow that a stage has landed, the real work begins. There is still a long way between this experimental landing and the ideal of saving money by reusing stages. So far, reuse is adding to SpaceX costs. - Ed KyleAs all R&D projects... first you spend, then you take benefits.And in fact this is not completely true. One of the biggest benefits for now will not be stage reusing. It will be the learning from used stages. Checking structural components would be one of the most important areas for future improvement. Let's say they had pulled this off in April, on a barge landing. And after the flight they could have seen that the helium tank support structure was not in good conditions, thus preventing the later failure.
Now that a stage has landed, the real work begins. There is still a long way between this experimental landing and the ideal of saving money by reusing stages. So far, reuse is adding to SpaceX costs. - Ed Kyle
There is no SpaceX stock.
And there will not be an IPO before there are lots of regular flights to and from Mars, the Elon said.
Technically, the rocket can do even better. Since the engines are known to re-start, you could shut down the center core in early flight, then restart the engines and use the saved fuel after the size boosters separate. This would take a lot of engineering courage, but gets most of the benefit of cross-feed without any hardware changes.
Quote from: Hauerg on 12/23/2015 08:32 pmThere is no SpaceX stock.There is, it's just that the public can't buy it.Quote from: HauergAnd there will not be an IPO before there are lots of regular flights to and from Mars, the Elon said.That just means the SEC will decide when SpaceX goes public, not Elon.
Quote from: LouScheffer on 12/23/2015 04:40 pmTechnically, the rocket can do even better. Since the engines are known to re-start, you could shut down the center core in early flight, then restart the engines and use the saved fuel after the size boosters separate. This would take a lot of engineering courage, but gets most of the benefit of cross-feed without any hardware changes.From an efficiency standpoint (if you don't have crossfeed) it would be best to have all 3 cores run at full power, stage when they are empty to get rid of their mass and let the lighter 2nd stage take over. That would make the entire rocket 2 stage and have the 3 1st stage cores return simultaneously.
The SEC rule involved for example with Facebook, specifies 500 shareholders "of record".
EM owns 60% and can control that detail. He won't be pushed into an IPO by the SEC before he's ready.
Quote from: Ludus on 12/24/2015 02:42 amThe SEC rule involved for example with Facebook, specifies 500 shareholders "of record".Those rules have a habit of changing overnight.Quote from: LudusEM owns 60% and can control that detail. He won't be pushed into an IPO by the SEC before he's ready.Dunno where that number comes from.
Pure goosebump stuff:
And it portrays it as if SpaceX is the only one doing anything in space...
Quote from: edkyle99 on 12/23/2015 05:09 amSpaceX is building it's own version of STS. Falcon Heavy will weigh close to 1,500 tonnes at liftoff and only lift 6.5 tonnes to GTO. A little better than Shuttle, and freed of the need to launch humans along with the cargo, but still a very big rocket. - Ed Kyle[...] Also, I'm pretty sure SpaceX is sand-bagging the GTO recoverable numbers. [Calculations deleted...] There is still some gravity loss involved, but staging should be at 3200 m/s or better. [More calcs deleted...] that's at least 8 t to a 1500 m/s deficit GTO.
SpaceX is building it's own version of STS. Falcon Heavy will weigh close to 1,500 tonnes at liftoff and only lift 6.5 tonnes to GTO. A little better than Shuttle, and freed of the need to launch humans along with the cargo, but still a very big rocket. - Ed Kyle
The transfer energy of Falcon Heavy will more than double that of Falcon 9. The maximum transfer energy is approaching a terajoule.
Quote from: CorvusCorax on 12/23/2015 10:58 pmQuote from: LouScheffer on 12/23/2015 04:40 pmTechnically, the rocket can do even better. Since the engines are known to re-start, you could shut down the center core in early flight, then restart the engines and use the saved fuel after the size boosters separate. This would take a lot of engineering courage, but gets most of the benefit of cross-feed without any hardware changes.From an efficiency standpoint (if you don't have crossfeed) it would be best to have all 3 cores run at full power, stage when they are empty to get rid of their mass and let the lighter 2nd stage take over. That would make the entire rocket 2 stage and have the 3 1st stage cores return simultaneously.This is not correct, since it ignores the benefits of saving some fuel until the accelerated dead mass is less. Here's a numerical example:Assume each core is 30 t empty, holds 420 t of fuel, ISP = 311, and a second stage mass of 125 t. The three boosters combined mass 90 t at burnout. So running all of them in parallel, as you suggest, the delta-V is 311*9.8*ln(1260 + 90 + 125)/(90 + 125)) = 5869 m/s imparted to the second stage.Now alternatively, use the two side cores to loft a full middle core. The the side cores burn 840 t of fuel to lift a payload of 575 t (420 fuel + 30 middle core + second stage). Thus the delta-V when the 2 cores burn out is: 311*9.8*ln((840+60+575)/(60+575)) = 2568 m/s. Then the middle core burns, adding 311*9.8*ln((420+30+125)/(30+125)) = 3995 m/s. That's a total of 6563 m/s imparted tp the second stage, about 700 m/s more than parallel staging. Of course your gravity losses are higher in the second case. You compromise by using full thrust at first, then throttle back to save more fuel for after staging.You don't need to take my word (or calculations) for this. Look at the Delta-IV heavy ( http://spaceflight101.com/spacerockets/delta-iv-heavy/ ). It takes off at full power, then throttles down the middle core at about 50 sec, well before acceleration limits kick in. The side cores run at full power until they run out of fuel, then they stage away and the center core resumes at full thrust. They do this precisely to maximize the delta-V in a non-crossfeed situation. Exactly the same logic will apply to the Falcon Heavy.
Quote from: LouScheffer on 12/24/2015 02:48 amQuote from: CorvusCorax on 12/23/2015 10:58 pmQuote from: LouScheffer on 12/23/2015 04:40 pmTechnically, the rocket can do even better. Since the engines are known to re-start, you could shut down the center core in early flight, then restart the engines and use the saved fuel after the size boosters separate. This would take a lot of engineering courage, but gets most of the benefit of cross-feed without any hardware changes.From an efficiency standpoint (if you don't have crossfeed) it would be best to have all 3 cores run at full power, stage when they are empty to get rid of their mass and let the lighter 2nd stage take over. That would make the entire rocket 2 stage and have the 3 1st stage cores return simultaneously.This is not correct, since it ignores the benefits of saving some fuel until the accelerated dead mass is less. Here's a numerical example:Assume each core is 30 t empty, holds 420 t of fuel, ISP = 311, and a second stage mass of 125 t. The three boosters combined mass 90 t at burnout. So running all of them in parallel, as you suggest, the delta-V is 311*9.8*ln(1260 + 90 + 125)/(90 + 125)) = 5869 m/s imparted to the second stage.Now alternatively, use the two side cores to loft a full middle core. The the side cores burn 840 t of fuel to lift a payload of 575 t (420 fuel + 30 middle core + second stage). Thus the delta-V when the 2 cores burn out is: 311*9.8*ln((840+60+575)/(60+575)) = 2568 m/s. Then the middle core burns, adding 311*9.8*ln((420+30+125)/(30+125)) = 3995 m/s. That's a total of 6563 m/s imparted tp the second stage, about 700 m/s more than parallel staging. Of course your gravity losses are higher in the second case. You compromise by using full thrust at first, then throttle back to save more fuel for after staging.You don't need to take my word (or calculations) for this. Look at the Delta-IV heavy ( http://spaceflight101.com/spacerockets/delta-iv-heavy/ ). It takes off at full power, then throttles down the middle core at about 50 sec, well before acceleration limits kick in. The side cores run at full power until they run out of fuel, then they stage away and the center core resumes at full thrust. They do this precisely to maximize the delta-V in a non-crossfeed situation. Exactly the same logic will apply to the Falcon Heavy.Unfortunately your example with only two side cores firing is impossible.The rocket would not lift off.Bad assumptions -> invalid results.Waiting for someone with more convincing arguments.
From an efficiency standpoint (if you don't have crossfeed) it would be best to have all 3 cores run at full power,
You don't need to take my word (or calculations) for this. Look at the Delta-IV heavy ( http://spaceflight101.com/spacerockets/delta-iv-heavy/ ). It takes off at full power, then throttles down the middle core at about 50 sec, well before acceleration limits kick in. The side cores run at full power until they run out of fuel, then they stage away and the center core resumes at full thrust. They do this precisely to maximize the delta-V in a non-crossfeed situation. Exactly the same logic will apply to the Falcon Heavy.
Unfortunately your example with only two side cores firing is impossible.The rocket would not lift off.Bad assumptions -> invalid results.Waiting for someone with more convincing arguments.