I haven't been following the threads much over the past week.My understanding of the difficulty of this landing attempt is that the booster may not survive reentry to even attempt the barge landing because it will be going ~ twice as fast at stage separation as the last launch.Is that about right?
- Here is what I see in the foreground blur, and its eye opening, at least to me - I see a conical structure which fits within the nozzle extension to hold the N2 tanks for thrusting and powering the grid fins and the hydraulic fluid supply, the center pusher, as well as whatever other bulky items are in the interstage. Perhaps that structure not only holds those items but also supports the nozzle during horizontal handling and launch, perhaps shipping too (does the interstage ship with the 2nd stage?). It never dawned on me before that these items are not arrayed around the perimeter or on the lower bulkhead (if there is one) but it makes sense that they needed all of the diameter to make the nozzle extension as large in diameter as possible. I wonder if the tanks and other items have always been in the center or if they just got moved there with the revised interstage and revised larger Mvac nozzle? I wonder why these items are mated but the cylindrical outer portion isn't there yet, what is the significance of this?
Thanks. So is that a Mvac 1D that we see on the front of the 1st stage?
The Interstage barrel is integrated after the avionics, inboard grid fin actuators, N2 thrusters, and their associated kit, and tripod-looking center pusher, are all attached to the top of the first stage.
Quote from: Wolfram66 on 03/10/2016 02:58 amFalcon 9 uses an open hydraulic system that has a separate tank of RP-1 (which is used as the hydraulic fluid) pressurized by Nitrogen near the interstage, which, after use, drains down back into the main RP-1 tank for "reuse" by the engines. I don't believe this is correct, and in any case what does it have to do with the ASDS? Wrong thread.Grid fin hydraulic thread is over here:http://forum.nasaspaceflight.com/index.php?topic=36536.0Back to ASDS topics, please...
Falcon 9 uses an open hydraulic system that has a separate tank of RP-1 (which is used as the hydraulic fluid) pressurized by Nitrogen near the interstage, which, after use, drains down back into the main RP-1 tank for "reuse" by the engines.
That it is RP-1 has not been confirmed. I'd suspect it is NOT RP-1 because they ran out of it, so it must be a separate reservoir and thus no reason to be RP-1.
Copied from elsewhere here:Quote from: Kabloona on 03/10/2016 07:41 amQuote from: Wolfram66 on 03/10/2016 02:58 amFalcon 9 uses an open hydraulic system that has a separate tank of RP-1 (which is used as the hydraulic fluid) pressurized by Nitrogen near the interstage, which, after use, drains down back into the main RP-1 tank for "reuse" by the engines. I don't believe this is correct, and in any case what does it have to do with the ASDS? Wrong thread.Grid fin hydraulic thread is over here:http://forum.nasaspaceflight.com/index.php?topic=36536.0Back to ASDS topics, please...I'm not sure Wolfram66 meant fins. I think it is explanation of how engine gimbal hydraulic operates. Any thought on that?Could it be that they run out of it on this flight and therefore were off center?Also, would this idea work on methane based engines?
There's no reason for it to be RP-1 if it's a separate open system that does not drain into the fuel tank.
Wolfram66 may be confusing the main engine TVC actuator system, which does use RP-1 as the hydraulic fluid, and the grid fin actuator system, which is a separate system with good reasons *not* to use RP-1 as mentioned above.
Quote from: Kabloona on 03/10/2016 03:29 pmWolfram66 may be confusing the main engine TVC actuator system, which does use RP-1 as the hydraulic fluid, and the grid fin actuator system, which is a separate system with good reasons *not* to use RP-1 as mentioned above.Those are not good reasons to not use RP-1. Those are plausible reasons why it would be possible if you already have good reasons not to use RP-1 (none of which were stated above). RP-1 makes a fine hydraulic fluid, and they have plenty of it around, so why wouldn't they use it?
Quote from: abaddon on 03/10/2016 03:50 pmQuote from: Kabloona on 03/10/2016 03:29 pmWolfram66 may be confusing the main engine TVC actuator system, which does use RP-1 as the hydraulic fluid, and the grid fin actuator system, which is a separate system with good reasons *not* to use RP-1 as mentioned above.Those are not good reasons to not use RP-1. Those are plausible reasons why it would be possible if you already have good reasons not to use RP-1 (none of which were stated above). RP-1 makes a fine hydraulic fluid, and they have plenty of it around, so why wouldn't they use it?One possible reason is that the grid fin actuators are probably off-the-shelf items which were developed and tested for use with conventional hydraulic fluid, so why bother with a requal program for changing hydraulic fluid? (I'm not a hydraulics expert, so maybe RP-1 can be safely substituted for any hydraulic fluid in any system *without additional testing*, but maybe not, I don't know.)
Don't forget that the grid fins are at the top of the stage (Interstage, I think?) If you used RP1, you would have to pump it from the bottom. Better to use a fluid reservoir near the grid fins.