It's always safer, for any individual mission, to take all the performance the first stage has got. So the customer has to accept that in return for a cheaper launch, they are accepting a higher chance of mission failure.
Quote from: LouScheffer on 09/02/2013 01:01 amBut otherwise, the customer is explicitly accepting a lower chance of mission success in return for a cheaper launch. And if they have somehow missed this point, I'm certain the competitors will be happy to point it out, and the insurance companies will use it as a reason to raise premiums.BOTH the first and second stages have a lot of margin. The second stage is going to do another very long burn after putting the payload into orbit. 200m/s would be fine. The odds are much greater that it simply wouldn't restart, which wouldn't affect the main payload.The main payload is tiny. It's comical how over-sized Falcon 9 v1.1 is for this mission. It's about 25 times more powerful than necessary. What the stages plan on doing after separation isn't likely to make any difference to the primary payload.
But otherwise, the customer is explicitly accepting a lower chance of mission success in return for a cheaper launch. And if they have somehow missed this point, I'm certain the competitors will be happy to point it out, and the insurance companies will use it as a reason to raise premiums.
The SpaceX press release was about a single Merlin 1d engine achieving the equivalent firing time of 10 full missions. Are you going to tell me that a single /ablative/ RS-68 was fired for more than 10 times a full mission duration burn? If so, can you give a press release?
Through a 28 test qualification program, the Merlin 1D accumulated 1,970 seconds of total test time, the equivalent run time of over 10 full mission durations, and is now fully qualified to fly on the Falcon 9 rocket.The program included four tests at or above the power (147,000 pounds of thrust) and duration (185 seconds) required for a Falcon 9 rocket launch.
Quote from: Robotbeat on 09/02/2013 01:29 amQuote from: LouScheffer on 09/02/2013 01:01 amBut otherwise, the customer is explicitly accepting a lower chance of mission success in return for a cheaper launch. And if they have somehow missed this point, I'm certain the competitors will be happy to point it out, and the insurance companies will use it as a reason to raise premiums.BOTH the first and second stages have a lot of margin. The second stage is going to do another very long burn after putting the payload into orbit. 200m/s would be fine. The odds are much greater that it simply wouldn't restart, which wouldn't affect the main payload.The main payload is tiny. It's comical how over-sized Falcon 9 v1.1 is for this mission. It's about 25 times more powerful than necessary. What the stages plan on doing after separation isn't likely to make any difference to the primary payload.Sure, for this mission I agree. But this will not be true for a mission using the full capacity of a 9R. In this case you have the risk that a second stage underperformance (as happened on a Delta a few months ago) could doom a mission which would have worked if re-usability was not attempted.
Quote from: Robotbeat on 09/02/2013 01:41 amThe SpaceX press release was about a single Merlin 1d engine achieving the equivalent firing time of 10 full missions. Are you going to tell me that a single /ablative/ RS-68 was fired for more than 10 times a full mission duration burn? If so, can you give a press release?See the paper above (I edited my post)And no, the SpaceX press release was not about a single engine (unless they built only one for the test program), it was about "the Merlin 1D":QuoteThrough a 28 test qualification program, the Merlin 1D accumulated 1,970 seconds of total test time, the equivalent run time of over 10 full mission durations, and is now fully qualified to fly on the Falcon 9 rocket.The program included four tests at or above the power (147,000 pounds of thrust) and duration (185 seconds) required for a Falcon 9 rocket launch.
Okay, so the qualification program was shorter. How is that a problem?
Quote from: Robotbeat on 09/02/2013 02:01 amOkay, so the qualification program was shorter. How is that a problem? It isn't a problem _except_ for that they _claimed_ that it was longer than usual, not shorter.And the differences are dramatic....
You need to keep in mind, that SpaceX only published the total time of qualification testing. Before that is development testing and that time is unknown.Also they tested the first stage core for nearly two complete burns, thats 2 x 9 x 180=3240 seconds. If you add the nearly 2000 seconds qualification testing you are at 5000 seconds. If you assume that the development testing was at least that much you arrive at 10.000 seconds total test time, which would be my guess.
Quote from: apace on 09/01/2013 10:17 pmUnneeded remark. I sent him an email and get back to this a soon as I have an answer from Bernd.Thanks, look forward to his response.
Unneeded remark. I sent him an email and get back to this a soon as I have an answer from Bernd.
Quote from: joek on 09/01/2013 11:00 pmQuote from: apace on 09/01/2013 10:17 pmUnneeded remark. I sent him an email and get back to this a soon as I have an answer from Bernd.Thanks, look forward to his response.I contacted the author of the article and he confirmed, that the part with the Munich Re is fiction and NOT based on facts.
The admonition to fly rather than propagandise in my signature is directed at SpaceX, I'm afraid. As much as I admire their ambition and Elon Musk's technological vision, I have noticed that they are much better at promising, scheduling and offering visions of the future than they are in actually launching rockets that meet their stated performance goals in anything approaching a timely manner. Seriously now, guys: the time for talk is over and the total focus must be on showing that there is substance behind it.
If the second stage underperforms by 200 m/sec (a made up number) and the mission fails ...
So, SpaceX's ramp-up rate is pretty similar to those for both Atlas V and Delta IV. And that's in spite of SpaceX bring out a redesign of their vehicle along the way, and not starting with an organization that had been doing launches at a steady rate for a long time, unlike Atlas V or Delta IV.I have to say this complaining that SpaceX is has been all talk and needs to start delivering rings hollow. SpaceX has been delivering very well so far.
Quote from: LouScheffer on 09/02/2013 01:01 amIf the second stage underperforms by 200 m/sec (a made up number) and the mission fails ... Seriously? Either you really don't get it or you are deliberately ignoring cherry-picked facts. That 2nd stage has been thoroughly tested and flight qualified based on that hot-fire test. Everything about the stage is tested and certified before it is ever mated with the 1st stage at the launch site, and then it is tested AGAIN as an integrated part of the whole, except for the hot-fire.