As for Block 4, how many flights is that version going to have, 1 or 2? Either the window for Block 4 is shrinking or the Block 5's are further away than we think.
I'm wondering if "Block 4" hasn't already flown, during the NROL 76 launch. That rocket used a new type second stage that performed a long coast exercise after NROL 76 deployment. The next Falcon 9 slated to launch Inmarsat 5 F4 appears to use the same type second stage (based on a low resolution image of the static test - I'll withhold final judgement until launch day). Perhaps "Block 4" uses this improved second stage while "Block 5" will incorporate the improved first stage to boost this "Block 4" second stage. Guessing, of course. - Ed Kyle
Hypothetically, if NROL-76 were the first Block IV launch... Would that justify the extra performance seen ?
Block 5 will have reusable TPS (my guess: carbon-carbon at least for parts of it) and legs that can fold back (i.e. without needing to be removed).
Quote from: macpacheco on 05/12/2017 08:34 pmHypothetically, if NROL-76 were the first Block IV launch... Would that justify the extra performance seen ?You completely lost me. Where have you seen any indication that the flight had extra performance?
Quote from: edkyle99 on 05/12/2017 07:47 pmI'm wondering if "Block 4" hasn't already flown, during the NROL 76 launch. That rocket used a new type second stage that performed a long coast exercise after NROL 76 deployment. The next Falcon 9 slated to launch Inmarsat 5 F4 appears to use the same type second stage (based on a low resolution image of the static test - I'll withhold final judgement until launch day). Perhaps "Block 4" uses this improved second stage while "Block 5" will incorporate the improved first stage to boost this "Block 4" second stage. Guessing, of course. - Ed KyleThe new type of 2nd stage, could simply have been the testing of an "add-on" kit to allow a long coast added to the 2nd stage for direct to GSO insertion.
Quote from: gongora on 05/14/2017 04:09 amQuote from: macpacheco on 05/12/2017 08:34 pmHypothetically, if NROL-76 were the first Block IV launch... Would that justify the extra performance seen ?You completely lost me. Where have you seen any indication that the flight had extra performance?I was observed that the NROL-76 mission had an unusually short S1 burn. Either a tiny payload or more thrust
Per a couple of posters on the r/spacex subreddit (who have heard from people who should know but can't out their sources, of course) supposedly the last two launches were Block 3 first stage, Block 4 second stage.
If Block 4 is the thrust upgrade then the performance of Block 5 shouldn't be much better than Block 4.