Author Topic: Refurbishment of Used Stages/Vehicles  (Read 212827 times)

Offline cebri

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Re: Refurbishment of Used Stages/Vehicles
« Reply #180 on: 01/16/2016 09:48 AM »
It would be interesting, if it was one of the two other engines, which had to perform the retroboost.

Does anyone have an idea how much work is required to replace an engine?

If they have plenty of them due to reuse of rocketstages, they could replace damaged engines and refurbish them seperately.

https://twitter.com/elonmusk/status/688175650570547202

Are we really talking here about a engine failure? From Elon tweets engine 9 seems to be working alright but the had some thrusts issues due to debris entering the engine (maybe coming from the main engine during descent?). Hopefully it will be an easy fix.

Can't wait to hear from Elon about the test they'll be doing tonight.

Edit:

Video of the static fire. (very poor quality)

« Last Edit: 01/16/2016 10:20 AM by cebri »

Offline The Amazing Catstronaut

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Re: Refurbishment of Used Stages/Vehicles
« Reply #181 on: 01/16/2016 10:31 AM »
If there was an engine failure it'd probably say failure. Thrust fluctuations can range from extremely minor and trivial or something more severe, but I'm calling a bit of coke shifting for some dust getting into the engine on landing. Remember, it wasn't the landing engine so it was somewhat more likely to take a chunk of FUD. Unlikely to be anything that can't simply be cleaned out.

If this had happened during a launch, $10 imaginary bucks say the rocket would have made orbit.
« Last Edit: 01/16/2016 10:32 AM by The Amazing Catstronaut »
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Offline Dante80

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Re: Refurbishment of Used Stages/Vehicles
« Reply #182 on: 01/16/2016 11:10 AM »
It's not the first time that we have seen engine thrust fluctuations in a SpaceX mission. SES-8 had something similar (you can also see the double TEA-TEB flash on this mission too).


Offline Rocket Science

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Re: Refurbishment of Used Stages/Vehicles
« Reply #183 on: 01/16/2016 01:50 PM »
Congrats SpaceX on a great test! 8)
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Offline watermod

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Re: Refurbishment of Used Stages/Vehicles
« Reply #184 on: 01/16/2016 04:02 PM »
Well if the engines are ~$1.5M, and if the Atlas slide is correct, than the F9 does not cost $60M. 

So something's gotta give.

It's an Atlas slide. Why would you assume F9 has identical cost breakdowns? It's a completely different vehicle.
Because apart from the engines, it's a similar structure, similar fuel, similar size...  It can't be THAT different.   If the Merlins are 1.5 Million, then the engine stack is 15M.  So the structures would have to be some 30M to get the entire rocket to 60M.   

That's very far from the Atlas breakdown...  2:1 instead of 1:2....

Yes, it can be very different. For one simple example that jumps out from the chart, I expect the cost of avionics is very different, and seems to be a good chunk of ULA's costs, by the pie chart shown.

ULA uses typical radiation resistant aerospace components and systems; SpaceX uses pretty COTS components for its systems and software, getting reliability by redundancy in the systems (many CPU's, etc), running much more modern software.  Given the cost of those modern components (which are far faster than anything you can get "radiation hardened"), I don't understand how to spend the kind of money that ULA current has to spend, despite having to have that redundancy; modern semiconductor technology and Moore's law being what it has been. SpaceX gave a talk at a Linux conference a few years ago describing (to the extent that the export control laws allow) what they were doing in their systems.

Sometimes, by revisiting systems from scratch, you can get to a very different (better) point that following the path of "incremental improvement".  Clean sheets can be a real advantage; but you don't get them very often.  SpaceX did a "clean sheet" on most everything.

So don't presume the actual costs in the different rockets are "the same", unless you are comparing fundamental costs (e.g. propellants, or N kilograms of aluminum alloy)...  And one of Musk's strengths is that he thinks terms of those fundamental costs, rather than what people have traditionally paid....

Since the first stage doesn't go into space, does ULA, SpaceX or any other company bother to use rad-hardened electronics on the first stage?   

If so, then why?

Offline guckyfan

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Re: Refurbishment of Used Stages/Vehicles
« Reply #185 on: 01/16/2016 04:43 PM »
Since the first stage doesn't go into space, does ULA, SpaceX or any other company bother to use rad-hardened electronics on the first stage?   

If so, then why?

From older pre Falcon 9 1.1 discussions I recall that first stages don't have avionics. Avionics are in the upper stage. Additional avionics in the first stage would be extremely expensive.

Offline randomly

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Re: Refurbishment of Used Stages/Vehicles
« Reply #186 on: 01/16/2016 04:49 PM »
Then how does a Falcon 9 first stage do RTLS without avionics?


Spacex doesn't use rad hard electronics for any of their avionics, it's all off the shelf technology with error check/correction and voting redundancies handling the errors.

Offline guckyfan

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Re: Refurbishment of Used Stages/Vehicles
« Reply #187 on: 01/16/2016 04:55 PM »
Then how does a Falcon 9 first stage do RTLS without avionics?


Spacex doesn't use rad hard electronics for any of their avionics, it's all off the shelf technology with error check/correction and voting redundancies handling the errors.

Right, of course the Falcon 9 first stage has avionics. I just repeat that old argument, which indicates a Atlas or Delta first stage would not have avionics.

Offline bjornl

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Re: Refurbishment of Used Stages/Vehicles
« Reply #188 on: 01/16/2016 06:22 PM »
(you can also see the double TEA-TEB flash on this mission too)
My guess: it's a single TEA-TEB firing which is obscured by the very bright RP-1 burning before the engines get to full thrust.

Offline Dante80

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Re: Refurbishment of Used Stages/Vehicles
« Reply #189 on: 01/16/2016 06:26 PM »
(you can also see the double TEA-TEB flash on this mission too)
My guess: it's a single TEA-TEB firing which is obscured by the very bright RP-1 burning before the engines get to full thrust.

It could be. There is a difference of 4 seconds between the two green flashes though.

Offline sanman

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Re: Refurbishment of Used Stages/Vehicles
« Reply #190 on: 01/17/2016 06:28 AM »
Hmm, so it's one of the outer engines (Engine 9) that's the culprit:

http://www.popsci.com/recovered-spacex-rocket-booster-is-in-great-shape


So if debris is coming into the engines, is that likely then happening during the descent through the atmosphere?

Offline Mader Levap

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Re: Refurbishment of Used Stages/Vehicles
« Reply #191 on: 01/17/2016 01:29 PM »
So if debris is coming into the engines, is that likely then happening during the descent through the atmosphere?
Not really. Maybe it is something from landing pad blasted by center engine or just soot.
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Online CorvusCorax

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Re: Refurbishment of Used Stages/Vehicles
« Reply #192 on: 01/17/2016 04:15 PM »

Since the first stage doesn't go into space, does ULA, SpaceX or any other company bother to use rad-hardened electronics on the first stage?   

If so, then why?

1. First stage does go into space. It does not go into orbit (it isn't going fast enough - although it could if it would launch without a second stage and payload weighing it down - but that would be a bit pointless) but it is going high enough - depending on mission over 200 km -  the official "borderline of space" is defined at 100 km altitude. Therefore the Falcon 9 1st stage is definitely a (suborbital) space faring vehicle.

2. Unlike almost all other space companies, SpaceX does not use radiation hardened electronics - instead they go for "radiation tolerant".  Rad hardened electronics mean chips with a structure size that was state of the art in the 1980's. That means their performance is sub par by roughly 30 years and they are also extremely expensive and in some cases very hard to get to.

Because of that, SpaceX choose an approach with multiple redundant layers of computers checking each other. If one of them misbehaves because of radiation, it will simply reset and start over, while the system keeps running on at least 2 other computers that check each other. The chance that multiple computers would make the exact same miscalculation at the same time due to radiation is almost non-existent.

Afaik this multi-redundant design has been used in aviation as an alternative to radiation hardened electronics. (On high altitude flights, cosmic radiation is also an issue) but its still new to go that path with rockets.


Offline Robotbeat

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Re: Refurbishment of Used Stages/Vehicles
« Reply #193 on: 01/17/2016 06:23 PM »
They may have to, but I imagine the first thing they'll try is additional redundancy. But I agree that someone within SpaceX will be working this, though I suspect the FH will be throwing stuff to Mars well within 10 years.
Quite likely but I think they'll be a rad level where every processor is in the process of reboot so none is processing any workload.
That's like 5 or 6 orders of magnitude difference. The difference in rad levels between LEO and deep space is much, MUCH smaller than that, just a factor of 2 or so different. And heck, you don't even need ANY redundancy... You could use just a watchdog timer hooked up to a reset. That's what is done on cubesats using off-the-shelf microcontrollers. People, as usual, make radiation to be this big scary thing that cannot be dealt with or which HAS to always be dealt with in a certain way.

Quote
Shielding would be another option, say a chunk of plastic (high H atom density)...
Not for electronics. Cosmic radiation is too low intensity to be a major concern. It's the much higher intensity but lower per-particle energy radiation from solar storms and passing through the South Atlantic Anomaly (when you're in LEO) that matter more. So metal is used for shielding electronics.
« Last Edit: 01/17/2016 06:25 PM by Robotbeat »
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Offline Adaptation

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Re: Refurbishment of Used Stages/Vehicles
« Reply #194 on: 01/17/2016 10:33 PM »
This image appears to show, at the base of the engine bells, what looks like a stitched material (curved, divided into relatively small squares by what looks like the stitching, darker black than most of surrounding image)?  Can that be true?  Either way, what is it and what are its likely eventual failure modes?



The engines are wrapped in a bullet proof shroud intended to prevent cascading failures in the event that an engine has a catastrophic failure.  This is what you see, I'm sure it also fulfills all the other uses mentioned earlier in the thread. 

Offline HMXHMX

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Re: Refurbishment of Used Stages/Vehicles
« Reply #195 on: 01/18/2016 02:40 AM »
This image appears to show, at the base of the engine bells, what looks like a stitched material (curved, divided into relatively small squares by what looks like the stitching, darker black than most of surrounding image)?  Can that be true?  Either way, what is it and what are its likely eventual failure modes?



The engines are wrapped in a bullet proof shroud intended to prevent cascading failures in the event that an engine has a catastrophic failure.  This is what you see, I'm sure it also fulfills all the other uses mentioned earlier in the thread. 

No, these only are the engine boat-tail gimbal boots, not armoring.  Same as the Delta IV image attached.

Offline Llian Rhydderch

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Re: Refurbishment of Used Stages/Vehicles
« Reply #196 on: 01/19/2016 10:09 PM »
I think this post by abaddon may have gotten missed by many in the rush of the new year. 

Since it has been more than 100 posts since it appeared, and since SpaceX accomplished a perfect zero-velocity at zero-altitude pinpoint-accurate barge touchdown since then, it is worth looking over this solid analysis once again.  SES-9, with barge landing planned to be attempted, will be a key data point for all of us, and a linchpin for predicting which future SpaceX missions can attempt a first stage recovery.  As abaddon concluded:  perhaps all of them.

Right now a significant number of their payloads need to use the margin they have for landing the stage so it can't be reused.
Shotwell has cited the main benefit of the F9FT is allowing a barge landing on flights that wouldn't have been able to in the past (GTO).  It has yet to be established just how heavy a payload the F9FT can throw to GTO and still carry legs and reserve propellant for a downrange landing.  A barge landing is estimated to require a ~15% performance margin.  I am guessing we won't really know for sure immediately as the next GTO payload (SES-9) is quite heavy.

According to Wiki the heaviest bird F9 has thrown to GTO was TurkmenAlem52E/MonacoSAT: https://en.wikipedia.org/wiki/TurkmenAlem52E/MonacoSAT at 4707kg.  According to Gunter's, SES-9 is 5330kg, so it will be the heaviest payload to GTO for F9 to date.

I threw together a quick table of upcoming flights and masses to get an idea of how many recovery flights might be possible over the next year or so.  I didn't spend a ton of time vetting these so some flights might have been delayed/canceled/whatever.  Masses are from Gunter's and I note when I am estimating based on a similar bird.  I categorized payload recovery as Yes, Probably, Possibly, and Unlikely based on mass and past history, and taking into account the ~33% payload increase to GTO that F9FT is supposed to provide.

Payload                        Mass     Dest   Recovery Possible?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jason-3                         533kg   LEO    Yes
CRS-8                             ?kg   LEO    Yes
CRS-9                             ?kg   LEO    Yes
SES-9                          5330kg   GTO    Possibly (based on evidence that a barge landing will be attempted)
SES-10                         5300kg   GTO    Possibly
Thaicom 8                      3100kg   GTO    Yes
ABS 2A, Eutelsat 117 West B   ~4000kg?  GTO    Possibly (based on ABS-3A, Eutelsat 115 West B mass)
JCSAT-14                      ~3400kg?  GTO    Probably (based on JCSAT-15 mass)
BulgariaSat-1                 ~3400kg?  GTO    Probably (based on JCSAT-15 mass, same SSL-1300 bus)
JCSAT-16                      ~3400kg?  GTO    Probably (based on JCSAT-15 mass)
KoreaSat-5                     4465kg   GTO    Possibly
Es'hail-2                     ~3000kg   GTO    Probably
CRS-11                            ?kg   LEO    Yes
CRS-12                            ?kg   LEO    Yes
Formosat-5                      525kg   SSO    Yes
Iridium NEXT 1                ~8000kg?  LEO    Yes (800kg x 9 + estimated adapter mass)
Iridium NEXT 2                ~8000kg?  LEO    Yes (800kg x 9 + estimated adapter mass)
Iridium NEXT 3                ~8000kg?  LEO    Yes (800kg x 9 + estimated adapter mass)
Iridium NEXT 4                ~8000kg?  LEO    Yes (800kg x 9 + estimated adapter mass)
Iridium NEXT 5                ~8000kg?  LEO    Yes (800kg x 9 + estimated adapter mass)

Based on this I count 15 likely recovery flights out of 20.  That's a far cry from "only a few flights" being possible for recovery.  And that's arguably conservative, as F9FT should have enough margin to recover anything that has previously flown on an F91.1 (up to 4707kg).

Corrections welcome, I am sure there is some stuff that will likely need to be fixed here.

Update: I've updated SES-9 and 10 to "possibly" based on news that an application for barge landing has been filed.  That means that, theoretically, all of the upcoming launches will allow for recovery.
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Offline intrepidpursuit

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Re: Refurbishment of Used Stages/Vehicles
« Reply #197 on: 01/22/2016 05:12 PM »
Regarding the double TEA-TEB flashes. We learned after Orbcomm that they control the TEA-TEB flow into the three central engines independently of the others, but not individually. Is it possible that we are seeing the 9 engines lit in 2 groups? Perhaps the 3 central engines and then the remainder?

It is extremely difficult to tell which engines are firing once the sound suppression water starts flowing. I noticed they don't seem to announce, "main engine start" during the countdown the way the shuttle did. Perhaps this is the norm with the F9FT countdown, or since even before that, and we didn't notice.

Offline chipguy

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Re: Refurbishment of Used Stages/Vehicles
« Reply #198 on: 01/22/2016 05:40 PM »

Since the first stage doesn't go into space, does ULA, SpaceX or any other company bother to use rad-hardened electronics on the first stage?   

If so, then why?

2. Unlike almost all other space companies, SpaceX does not use radiation hardened electronics - instead they go for "radiation tolerant".  Rad hardened electronics mean chips with a structure size that was state of the art in the 1980's. That means their performance is sub par by roughly 30 years and they are also extremely expensive and in some cases very hard to get to.

I'd say that 15 to 20 years is more accurate.

By the way, it is possible to use more recent mainstream semiconductor process technology to build relatively
radiation hardened processors and ASICs using specific techniques in circuit design, logic design, and layout.
This is done in mission critical computers (mainframes and high end Unix servers) where the goal is to make
the chance of an undetected error under normal terrestrial background radiation extremely close to zero over
the operating life of the machine (a decade or more).

The problem is the market volumes for rad hard are so small it is hard to justify the extra design effort (which
would also makes the devices somewhat larger, slower, and more power hungry than straight commercial
products) or going the usual way, the expense of keeping a true rad hard process in production and porting
over an obsolete commercial processor design under license.

Offline oldAtlas_Eguy

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Re: Refurbishment of Used Stages/Vehicles
« Reply #199 on: 01/22/2016 11:34 PM »

Since the first stage doesn't go into space, does ULA, SpaceX or any other company bother to use rad-hardened electronics on the first stage?   

If so, then why?

2. Unlike almost all other space companies, SpaceX does not use radiation hardened electronics - instead they go for "radiation tolerant".  Rad hardened electronics mean chips with a structure size that was state of the art in the 1980's. That means their performance is sub par by roughly 30 years and they are also extremely expensive and in some cases very hard to get to.

I'd say that 15 to 20 years is more accurate.

By the way, it is possible to use more recent mainstream semiconductor process technology to build relatively
radiation hardened processors and ASICs using specific techniques in circuit design, logic design, and layout.
This is done in mission critical computers (mainframes and high end Unix servers) where the goal is to make
the chance of an undetected error under normal terrestrial background radiation extremely close to zero over
the operating life of the machine (a decade or more).

The problem is the market volumes for rad hard are so small it is hard to justify the extra design effort (which
would also makes the devices somewhat larger, slower, and more power hungry than straight commercial
products) or going the usual way, the expense of keeping a true rad hard process in production and porting
over an obsolete commercial processor design under license.
There are rad hard multiple core (2) PowerPC processors running at 800MHz which are about 10 years out of date compared to current state of the art processors. So it is not as bad as it seems but if you need high power capability for something like image (objects in an image) recognition for automatic robotic functions, using a Rad hard processor is just not going to be enough.

There are ARM processors, AMD and Intel ones as well but all of them are also around the 10 year ago capability mark level meaning they have about 100 times less processor throughput than current processors.

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