Author Topic: General Falcon and Dragon discussion (Thread 13)  (Read 396590 times)

Offline Kabloona

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #180 on: 02/25/2016 08:49 pm »
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?

On OG2, stage sep was at about 5000 km/hr. On this launch, stage sep will be at around 8000-9000 km/hr.

http://forum.nasaspaceflight.com/index.php?topic=34077.msg1495022#msg1495022

So not quite twice as fast. But main issue is limited propellant reserve for the entry burn, which means stage can't bleed off as much speed as would be optimal, so it may be a bit of a dice-roll as to whether it survives entry.
« Last Edit: 02/25/2016 08:56 pm by Kabloona »

Offline rickyramjet

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #181 on: 02/25/2016 09:41 pm »
Question (if anyone knows): Going forward, will the F9FT always have to use super chilled fuels, or can SpaceX still opt for standard temperatures on lower performance launches?

Offline MrHollifield

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #182 on: 02/25/2016 09:53 pm »
AIUI, the tanks were reconfigured for densified LOX, so loading with "standard" LOX would result in not enough LOX being loaded to burn all of the RP1. The turbopumps were also rebalanced for densified LOX, so the burn ratio probably wouldn't be right, either. So, I think they'll be using subcooled propellants on all future F9 flights (except maybe IFA on the old F9R Dev 2).

Offline OxCartMark

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #183 on: 02/29/2016 02:59 am »
I wrote the following last week in the Falcon production rate thread after seeing the (seemingly intentionally) blurred hardware at the top end of one F9 stage in the foreground right of the first picture below.

- 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?

Then during the webcast tonight over John Insprucker's shoulder I saw something that I don't recognize (the second picture below) that may be the same thing.  Does anyone recognize what this is in the second image?
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Offline dorkmo

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #184 on: 02/29/2016 04:26 am »
i think thats one of the first recovered dragons they have hanging from the ceiling

Offline nrubin

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #185 on: 02/29/2016 05:20 am »
It's actually a Merlin Vacuum engine (a 1-C model).  You can see this engine hanging from the ceiling here: https://twitter.com/SpaceX/status/426784049986682881.  Some more detail on a similar engine can be found here: http://spacefellowship.com/news/art19992/preparations-for-first-falcon-9-launch.html.

Offline OxCartMark

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #186 on: 02/29/2016 12:32 pm »
Thanks.  So is that a Mvac 1D that we see on the front of the 1st stage?
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Offline cscott

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #187 on: 02/29/2016 01:52 pm »
Thanks.  So is that a Mvac 1D that we see on the front of the 1st stage?
No, I think you were right the first time that it is the internal components of the interstage.  If you look at the less-finished stage on the back left corner in your photo I believe you see two concentric metallic rings which are the mounting hardware for this stuff.

The blurred-out front right stage has some components mounted to those rings.  I'm not sure it's actually a "conical structure", though: the blurry equipment might just be bolted directly to the ring.  The concentric mounting rings give it the conical appearance, perhaps, but I think that's misleading.  Can't tell if there's something mounted to the center dark area; there may or may not be.
« Last Edit: 02/29/2016 03:33 pm by cscott »

Offline The Roadie

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #188 on: 02/29/2016 02:41 pm »
Was just there for a tour on Saturday. The M1C-Vac hanging from the ceiling has the bottom part of its fuel tank (and some bafflery) as part of the mechanical structure that stays with it.

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. The Interstage barrel now goes out the door on the truck attached to the first stage.
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Offline Kabloona

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #189 on: 02/29/2016 03:39 pm »
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.

The grid fins and GN2 thrusters are attached to the bottom of the interstage, not the top of the first stage.
« Last Edit: 02/29/2016 03:40 pm by Kabloona »

Offline schaban

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #190 on: 03/10/2016 01:48 pm »
Copied from elsewhere here:

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.

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=36536.0

Back 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?



Offline abaddon

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #191 on: 03/10/2016 02:03 pm »
It's been said here (and I believe confirmed) that the grid fins are powered by an "open" hydraulic system; open meaning that the hydraulic fluid (RP-1) is vented out of the rocket, rather than being collected or routed to the engines.  IIRC the first attempt at a soft landing in the ocean with grid fins failed due to an insufficient supply of fluid.

Offline Robotbeat

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #192 on: 03/10/2016 02:12 pm »
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.
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Offline llanitedave

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #193 on: 03/10/2016 03:18 pm »
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.


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.  If it's dumped overboard, it could just as easily be canola oil.
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Offline Kabloona

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #194 on: 03/10/2016 03:29 pm »
Copied from elsewhere here:

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.

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=36536.0

Back 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?

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.
« Last Edit: 03/10/2016 03:34 pm by Kabloona »

Offline Jim

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #195 on: 03/10/2016 03:34 pm »

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.

Yes, there is.  One less logistics item.

Offline abaddon

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #196 on: 03/10/2016 03:50 pm »
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.
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?
« Last Edit: 03/10/2016 03:51 pm by abaddon »

Offline Kabloona

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #197 on: 03/10/2016 06:37 pm »
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.
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.)
« Last Edit: 03/10/2016 07:02 pm by Kabloona »

Offline inventodoc

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #198 on: 03/10/2016 07:57 pm »
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.
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.

Offline Kabloona

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Re: General Falcon and Dragon discussion (Thread 13)
« Reply #199 on: 03/10/2016 08:08 pm »
Quote
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.

I think we all believe that the reservoir is in the interstage. The question is, what do they fill the reservoir with?

The people who suggest it's RP-1 are saying so because there's plenty of RP-1 on hand at the launch site with which to load the reservoir before launch, not because they assume it gets pumped up from the rocket's main fuel tank.


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