Author Topic: History: ASDS Generators customization and outfitting  (Read 3859 times)

Online Eer

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Searching on the Web for information about SpaceX and I ran across this https://www.nov.com/about/nov-today-podcast/episode-4-nov-and-spacex podcast.  It tells the story, from the perspective of the company they contracted (NOV - https://www.nov.com/) with for generators for the ASDS, of working with SpaceX, not knowing who they were to begin with, and the minor mods necessary to "battleshort" the generators so they wouldn't shut down unless manually ordered to.

Search on the NSF didn't turn up a reference, so I thought I'd post it here for posterity.  Interesting historical tidbit, I thought.
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Offline Nomadd

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Re: History: ASDS Generators customization and outfitting
« Reply #1 on: 07/16/2020 02:45 pm »
 The first time I heard that term was during my first response with MSRC. A gasoline barge at Staten Island couldn't keep it's newly installed pumps going, so they just disabled all the safety shutoffs. Then when the line popped off, amazingly because they tied the barge off to the main output pipe, the pumps just kept pumping. It was still going when I got there two hours later.
 The initial explosion was bad enough, but you have to fast forward quite a ways to see the results of all the blown out valves and additional disabled safeties. The fire was over a quarter mile wide by the time it stopped growing.
 Our ship was just to the right of that little tanker in the foreground. It broke a few records getting away from the dock.

« Last Edit: 07/16/2020 02:48 pm by Nomadd »
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Offline Hog

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Re: History: ASDS Generators customization and outfitting
« Reply #2 on: 07/17/2020 01:55 pm »
From the podcast

"09:12 Garrett Williams: We did have to do some minor modifications overall. They were offshore-approved, so they were essentially already ready to go offshore for that application. The one modification we did do, it's actually called a "battleshort". And what a battleshort is, is you typically hear about this in military application, and what it means is you're taking off every safety measure from the unit outside of a manual emergency shutdown. So when you set a unit up for battleshort, you're rigging it to where regardless of oil pressure, regardless of cooling temperature, which our safety measures made in order to protect the engine, they want to eliminate all of those."

"Battleshort"  akin to commanding "Limits to inhibit" on an RS-25, or any other high dollar rocket/jet/reciprocating piston engine. 

I'd assume that at the time of purchase, the buyer must choose one of the following terms, "battleshort" OR "warranty"?

I like that term  "battleshort".  Right up there with "jumboisation", which is the lengthening of a ship by cutting the ship in two, and then installing a new section.  The Viking Jagre/Gentle Giants/Seawise/Knock Nevis underwent jumboisation to make it the largest ship in the world, greatest deadweight tonnage and she displaced 657,019 tonnes, 1,504.10 ft).  When fully loaded her draft wouldn't allow her to pass through the English Channel (81ft/24.6 meters).


The SLS Core Stage transport barge "Pegasus" under went jumboisation for NASA. Pegasus was 260 feet long for Shuttle, she is now 310 feet for SLS.  I wonder if Pegasus would get up on plane if they opened up the back doors and fired up the 4 RS25's?

attachments
1) Knock Nevis full
2) Knock Nevis empty
3) NASA Pegasus barge
4) Pegasus barge in drydock undergoing jomboisation (2014/15)
« Last Edit: 07/17/2020 02:00 pm by Hog »
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Offline CameronD

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Re: History: ASDS Generators customization and outfitting
« Reply #3 on: 07/20/2020 04:22 am »
From the podcast

"09:12 Garrett Williams: We did have to do some minor modifications overall. They were offshore-approved, so they were essentially already ready to go offshore for that application. The one modification we did do, it's actually called a "battleshort". And what a battleshort is, is you typically hear about this in military application, and what it means is you're taking off every safety measure from the unit outside of a manual emergency shutdown. So when you set a unit up for battleshort, you're rigging it to where regardless of oil pressure, regardless of cooling temperature, which our safety measures made in order to protect the engine, they want to eliminate all of those."

"Battleshort"  akin to commanding "Limits to inhibit" on an RS-25, or any other high dollar rocket/jet/reciprocating piston engine. 

I'd assume that at the time of purchase, the buyer must choose one of the following terms, "battleshort" OR "warranty"?

Potentially.  I must admit I have never heard of anyone removing the safeties from marine generators (but then that experience was with emergency generators on passenger vessels, so there were plenty of people standing by ready to push the stop button whenever the thing was running) and can't quite understand why SpX would request this for ASDS operation.

I can see why they might consider "battleshorting" the generators given thruster shutdown at a critical moment might end in disaster for the incoming stage, however given that the ASDSs are also unmanned hence there's no-one around to push the stop button on a genuine shutdown event (eg. low oil pressure), I would think an irreparably damaged ("boat-anchored") generator a long way out to sea plus/minus an engine fire might still end in disaster.

A better option, as used on shipping world-wide to maintain command & control if the emergency gen fails, is called a TPS (Transitional Power Supply) - it's kinda like a UPS only much, much bigger and lasts only long enough to get another source of power on-line ..or a mayday call out.

« Last Edit: 07/20/2020 07:13 am by CameronD »
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Offline John Alan

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Re: History: ASDS Generators customization and outfitting
« Reply #4 on: 07/20/2020 05:16 am »
I could understand a request to be able to remotely on command disable the shutdowns...

My guess is the Genset are started with crew on the barge once it's towed into position...
T- 1 hour or something...
Everything warms up and is running fine on the safeties when the call comes to get off the barge...
T- 30 mins or something...
The crew takes one final look at the hard gauges and walks off the barge onto a waiting ship...
Would not surprise me in the least that there are also remote gauges on the support ship via network connection...

At say T- 10 mins... MCC polls all sections and one is recovery...
IF the gauges all still read green... Recover is GO...

At T- 45 secs... on Go for launch or whatever... Recovery bypasses the Genset safeties... Your "battle short" mode

NOW... the odds of a genset that has been running fine the last hour under load, suddenly overheating or losing oil pressure or worst in the next 10 mins is slim IMHO... 
And even if it dies a slow death, it will likely stay up in some fashion for that same 10 mins...

I have seen and heard of bigger engines that ran right up until you unload them... then they break or RUD...
Tractor engines...Locomotive engines... Construction equipment engines... I have heard stories on all those...
I witnessed a Tractor engine spin a Main and seize the instant the op pushed in the clutch...
EMD 641's are famous for only throwing rods when you unload them and not before... so I have heard...
 
And we have all seen the YT videos or seen in real life people taking junk cars and cutting the rad hoses and draining the oil pan and putting a brick on the accelerator...
I know a guy in Texas who's wife ran over a concrete block on the freeway... and then drove 30 miles home with the dash lit up like a Christmas tree... The block tore the oil pan open and took out the rad...
New oil pan and rad... and it's still on the road last I heard...

SO... I think this whole thing is overblown... this is all just risk management...

Offline john smith 19

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Re: History: ASDS Generators customization and outfitting
« Reply #5 on: 07/20/2020 05:49 am »
Somewhat relevant.

XCOR did this with some of their engines IIRC. You want that to keep running as long as possible.

As others have noted if an engines been running for hours under exactly the same (normal, not exceptional) conditions it seems reasonable that it could last another X minutes without total failure. If those X minutes are critical to making a system work and it's not too important what happens after that, then this makes perfect sense.

Since it's a standard option it also makes the process more straightforward than constructing some kind of ad-hoc one off temporary power supply, which I've seen for high reliability applications in certain businesses (basically a huge block of batteries that last long enough for the backup generators to kick in. Or not, if they were not charged.  :(  ).
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Offline Robotbeat

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Re: History: ASDS Generators customization and outfitting
« Reply #6 on: 07/23/2020 02:35 pm »
I mean, the analogy to battle is apt.

If the generator stopped due to low oil pressure or something 120 seconds before a rocket landed, causing the ship to move out of position and have the rocket “land” in top of a generator and then topple over, it’s a lot like getting fire-bombed. Seized engine is better than getting fire bombed.
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Offline John Alan

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Re: History: ASDS Generators customization and outfitting
« Reply #7 on: 07/24/2020 11:11 am »
I feel compelled to point out what a set of three or more 3 phase diesel generators do and act like when they are started up and then paralleled onto one electrical bus...

For my example, I will use 4 gen sets... for easy math...

Spec max site load... 1000 kWh or 1 MWh...
Buy or lease 4 x 334+ kWh... or 3 and a spare if you will... or 5 x 334+kw and have 3 plus two spares...

The typical automation will just sit there, all units talking to each other in silence over RS485 or a later tech network... UNTIL a circuit called the start circuit (two wires to some SPST switch or relay opens... dropping that circuit to a failed 0-volt DC state...
Be aware, all EACH main circuit breakers AT each generator have automation that lets the Genset controller for that engine open and close it on local set command... it's part of a Genset that can be paralleled... Required...

All enabled Getsets (in standby and NOT locked out, tagged out for maintenance or whatever) see that 0-volts DC signal and ALL units... All 4 in our example, attempt to start and get to speed... It's a race...
Again... in our example where they all are talking on their RS-485 local net... and they are jabbering at each other like crazy... reporting their current state on broadcast...
Finally one reports I'm there, 60hz, 277/480 volts, on all three of my phases... the main bus shows 0 on all meaning I AM first and will close my main in 3, 2, 1... NOW...
BANG... and the main buss is alive and the lights in the hospital ICU and surgery and some hallways spring back to life...

(I'm told an EMD/CAT 2 stroke 645/710 series gen set with dual multiple air starters and all the heaters and lubers can safely go from standing still to full power in under 15 seconds... Cummins 4 strokes take about 30 seconds...
EMD 710 can now be had new with tier 4F certification as long as it's a large install (boat or land) and has DEF tanks...
Sadly it's days in new build locomotives are over...  :( :end shameless CAT plug)

(in my hospital stays back in 08 and again in the last year, my take on modern hospital equipment is they all each run on its own battery with the plug simply there as a way to continually recharge the battery... This spreads the failure points across many points but they are points that only may affect one life, not many, data centers typically have one UPS per rack of servers, my own PC here I am typing on has a 1300w sine wave UPS that is the battery always with the plug only topping it up... I'm drawing~ 175 watts as I type this...  :D )

(see in a complex system, there will and is more than one bus transfer switch connected to the utility and the gen buss... ASDS may have one on each prop pair is my guess...and it may listen to the same RS485 bus and limit its usage until more power becomes available)

The other 3 sets see the main bus come alive and watch it while listening on the RS-485 and still trying to get stable too...
Each controller tries to match freq (engine speed), then voltage (exciter volts), then (and this is critical) phase angles on the 3 phases by tweaking it's engine governor till it too sees a perfect match... then 3,2,1 BANG and it's breaker closes...
I'm up too (it jabbers)... then they all start reporting their load percent... if they are over 50% each for 2 units up... the two units lagging and offline keep trying to 'sync' as they say... and the utility switches in the hospital stay at critical loads only for now...

The next Genset unit reports 3,2,1 Bang... and the jabbering continues... 3 at say 20% they all say... The hospital system responds by closing more transfer switches until it's load reaches just under 33% for 3 or all systems online...
The one last Genset finally reports 3,2,1 Bang... and the loads drop below 25% across the board and the hospital system turns everything on and reports to security that they can tell staff to restart any and all system... return to normal, please... the system may even then put the highest runtime hour set on standby again to even the wear and tear across the units... and get the rest up into a more fuel-efficient load range (over 70% is my understanding)

Now then... of course a hospital has full shutdown safeties on their Gensets along with Jacket water heaters and Prelube pumps pumping warm oil to engines just sitting there... or if there are surgeries ongoing, one unit may be running already... all-natural gas units and may even have LPG+air dilution or some other backup fuel supply... or all diesel and buy fuel to keep the tanks topped up...

ASDS only has so much fuel onboard... it gets towed out with maybe a small aux Genset running or maybe even cold and dark... I do not know...
My guess, is once on station (towboat circling slowly around the target) someone boards and manually picks the first unit to start... starts it and lets it stabilize and warm up a bit... then manually closes its breaker via automation...
Starts the 2nd unit and once warmed up tell it to sync to the first... and so on till all units aboard are up and there is enough power to then start thrusters up in some sequence manually... (powered but not thrusting yet)
Towboat slows to a crawl and heads right at target coordinates... On cue, the system on the barge is activated...
Towboat suddenly notices the barge is fighting back and stops and slacks the tow cable... maneuvers to stay out front as the barge systems rotate the heading to face the best way for current wind and sea states...
Crews disconnect the tow and it retreats a bit... sticks around till everything looks good then retreats fully...

Ok... ASDS electrical thruster loads are likely high and all over the place when fighting a gusty wind and waves...
And truth be told, a generator rated at say 500kw can put out way more then that for short periods...
Your true limits are full fuel at the engine governor and generator windings or other wiring melting and shorting out...   
1000 kw (2 x rated) for 10 minutes is NOT unreasonable for the Genset windings to heat soak to an insulation melting point...
SO... my understanding of a "Battle Short" generator setup is not hard to do... for a paralleled setup...
Add a set of fuses between the current main Genset controlled breaker and the gen and populate with whatever the requirement is based on best guess (or found in actual load bank testing) for max fuel and winding lasting minutes at that fuel rate plus at least 20%)
You do this IN CASE the engine does seize and/or RUD on you... as the other Gensets will see the locked or slow gen as a HUGE added electric motor load if you do not add this...
You added a DPDT relay into the breaker control circuit and wire it straight to the engine starting battery... and generator output... oh and wire it so it's engaged unless you open a switch somewhere...
Do the same to the engine shutoff... defaults to max and run and is enabled to listen to the Genset controller and it's nanny state...

As long as the engine is still turning in-phase and putting out enough power to turn itself... it will be helping feed the circuit...
As soon as things go awry enough, the other generators will end that automatically by popping the fuses on the bad unit... Popping the fuses results in the engine relay and transfer gizmos going back into off and nanny state and the engine will for sure shut down with the nanny firing all its safety equipment such as fire fighting equipment if it was so equipped and set up right...

ANYWAY... wanted to get that out there and let you know what I know on the topic after some research and picking the brain of someone "in the business" that I know... (they sometimes build military sets)...

 ;)  8)

On edit added... 3500 KW - EMD 710 - V20 - 5000 hp startup and loading test video...
Its site requirement is starting and idles first then ramp to full speed slowly (900 rpm) and engage breaker within 2 mins... This is a typical no pre lube start setup but it does have jacket heaters as this allows starts without blowing down the cylinders from water seeps and condensation from a cold engine sitting...
Quote
these v20 engines are used mainly for emergency backup
generators that are powered up and taken to full load within 2 minutes. each cylinder has a displacement of 11.6 litres.


The V-20 was used in the SD45 and SD80MAC locomotives and in pairs in 10000hp tugboats...
The V-16 version is found in THOUSANDS of SD40 and SD70MAC locomotives still in use and being rebuilt under grandfathered Tier 1+ standards with upgrades to Electronic fuel injection and new engine controllers... Typically these are set at 4400hp and live about 1 million miles between overhauls if taken care of...
This is totally legal in the USA and railroads like NS are literally picking locomotives with good engine blocks and mainframes and replacing Cabs with new crashworthy stuff and adding the required intercoolers with EMD kits available...
Basically get a like-new zero-hour locomotive for about 1/2 the cost of a new T4F unit...
The toilet is clean and it has that new car smell and glossy paint job...
Then the railroad send it out on the rails for 6 months between oil changes and put 200,000+ miles a year on it...  :P
UP railroad keeps EMD and GE alive by buying about 25 + 25 new each year and everyone else either rebuilds their own or contracts it out back to Progress Rail/CAT or other shops... NS is taking a bunch of their 90's vintage Dash 9 GE's and totally rebuilding including swapping DC for AC traction motors (more torque and traction control improvements)
« Last Edit: 07/24/2020 04:44 pm by John Alan »

Offline Twark_Main

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Re: History: ASDS Generators customization and outfitting
« Reply #8 on: 07/25/2020 09:21 pm »
[snip]

I mean yea, I was gonna say that... ;D

Seriously though, great post. A wealth of information.
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Offline john smith 19

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Re: History: ASDS Generators customization and outfitting
« Reply #9 on: 08/03/2020 05:42 am »
I feel compelled to point out what a set of three or more 3 phase diesel generators do and act like when they are started up and then paralleled onto one electrical bus...

For my example, I will use 4 gen sets... for easy math...
Thank you that was highly detailed.

What's so remarkable is it's resemblance to the whole Shuttle GPC/SSME start and running process, with the SSME controllers reporting to the GPC's and the GPC's talking to each other to stay in sync to detect a disagreement (implying a sensor fault or a software failure) between them.
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