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SpaceX Vehicles and Missions => SpaceX Missions Section => Topic started by: gongora on 06/20/2018 06:27 pm

Title: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: gongora on 06/20/2018 06:27 pm
CRS-16 Discussion thread

NSF Threads for CRS-16 : Discussion (https://forum.nasaspaceflight.com/index.php?topic=45881.0) / Updates (https://forum.nasaspaceflight.com/index.php?topic=46901.0) / CRS-16 Dragon Updates after launch (https://forum.nasaspaceflight.com/index.php?topic=46944.0)
NSF Articles for CRS-16: https://www.nasaspaceflight.com/?s=CRS-16 (https://www.nasaspaceflight.com/?s=CRS-16)

NSF Articles for CRS missions :  https://www.nasaspaceflight.com/?s=CRS (https://www.nasaspaceflight.com/?s=CRS)

Successful launch December 5, 2018 at 1:16pm EDT (18:16 UTC) on Falcon 9 (new booster 1050) from SLC-40 at Cape Canaveral. The Dragon capsule was previously used on the CRS-10 mission.  RTLS landing was expected, but a grid fin failure resulted in the booster coming down in the water a couple of miles offshore.



External cargo: GEDI, RRM3



Other SpaceX resources on NASASpaceflight:
   SpaceX News Articles (Recent) (http://www.nasaspaceflight.com/tag/spacex/)  /   SpaceX News Articles from 2006 (Including numerous exclusive Elon interviews) (http://forum.nasaspaceflight.com/index.php?topic=21862.0)
   SpaceX Dragon Articles (http://www.nasaspaceflight.com/tag/dragon/)  /  SpaceX Missions Section (with Launch Manifest and info on past and future missions) (https://forum.nasaspaceflight.com/index.php?board=55.0)
   L2 SpaceX Section (https://forum.nasaspaceflight.com/index.php?board=60.0)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: gongora on 06/20/2018 06:38 pm
GEDI (Global Ecosystem Dynamics Investigation)

GEDI Home Page at UMD (https://gedi.umd.edu/)

Quote
May the Forest Be With You: GEDI Moves Toward Launch to Space Station (https://www.nasa.gov/feature/goddard/2018/may-the-forest-be-with-you-gedi-to-launch-to-iss)

May 4, 2018

A first-of-its-kind laser instrument designed to map the world's forests in 3-D is moving toward an earlier launch to the International Space Station than previously expected.

The Global Ecosystem Dynamics Investigation – or GEDI, pronounced like "Jedi," of Star Wars fame – instrument is undergoing final integration and testing this spring and summer at NASA's Goddard Space Flight Center in Greenbelt, Maryland. The instrument is expected to launch aboard SpaceX's 16th commercial resupply services mission, targeted for late 2018. GEDI is being led by the University of Maryland, College Park; the instrument is being built at NASA Goddard.

“Scientists have been planning for decades to get comprehensive information about the structure of forests from space to deepen our understanding of how this structure impacts carbon resources and biodiversity across large regions and even globally, as well as a host of other science issues,” said Ralph Dubayah, GEDI principal investigator and a professor of geographical sciences at the University of Maryland. “This is why seeing the instrument built and racing toward launch is so exciting.”

From its perch on the exterior of the orbiting laboratory, GEDI will be the first space-borne laser instrument to measure the structure of Earth's tropical and temperate forests in high resolution and three dimensions. These measurements will help fill in critical gaps in scientists' understanding of how much carbon is stored in the world's forests, the potential for ecosystems to absorb rising concentrations of carbon dioxide in Earth's atmosphere, and the impact of forest changes on biodiversity.

GEDI will accomplish its science goals through an ingenious use of light. The instrument is a lidar, which stands for light detection and ranging. It captures information by sending out laser pulses and then precisely measuring the light that is reflected back.

GEDI's three lasers will produce eight ground tracks – two of the lasers will generate two ground tracks each, and the third will generate four. As the space station and GEDI orbit Earth, laser pulses will reflect off clouds, trees and the planet's surface. While the instrument will gather height information about everything in its path, it is specifically designed to measure forests. The amount and intensity of the light that bounces back to GEDI's telescope will reveal details about the height and density of trees and vegetation, and even the structure of leaves and branches within a forest's canopy.

NASA has flown multiple Earth-observing lidars in space, notably the ICESat (Ice, Cloud and land Elevation Satellite) and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) missions. But GEDI will be the first to provide high-resolution laser ranging of Earth's forests.

https://youtu.be/XjieZ9iZHWs
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: gongora on 06/20/2018 06:49 pm
RRM3 (Robotic Refueling Mission 3)

RRM3 Home Page at Goddard (https://sspd.gsfc.nasa.gov/RRM3.html)
Quote
RRM3 Primary Objectives
1. Perform cryogenic liquid methane transfer in micro-gravity
2. Maintain cryogen fluid mass for six months via zero boil-off

RRM3 Secondary Objectives
1. Demonstrate and validate the Compact Thermal Imager - An instrument that utilizes available room on RRM3 to observe Earth to detect smoke and fires, as well as measure crop transevaporation.
2. Complete Machine Vision Tasks - In-space assessment of fiducials (decals) with unique patterns that enhance machine vision algorithms and aid in autonomous rendezvous and tool positioning.

Quote
Robotic Refueling Mission 3 Completes Crucial Series of Tests (https://www.nasa.gov/feature/goddard/2018/robotic-refueling-mission-3-completes-crucial-series-of-tests)

June 20, 2018

Space exploration has captured our attention for over half of a century. NASA plans to propel human spaceflight beyond low-Earth orbit and continue the legacy of the Apollo missions.

With a renewed focus on exploration, NASA is developing new space technologies and capabilities that pave the way for missions back to the Moon and beyond. The agency will advance long duration mission-critical capabilities with the Robotic Refueling Mission 3 (RRM3).

From the International Space Station, RRM3 will demonstrate cutting-edge technologies to store and transfer liquid methane in space. Once proven, the methods can be applied to the storage and transfer of other cryogenic fluids – fluids with extremely low boiling points that can function as a coolant or propellant – for a variety of missions.

RRM3 recently concluded a crucial series of tests at NASA’s Kennedy Space Center in Cape Canaveral, Florida. Tests confirmed its electrical compatibility with the space station and validated successful methane operations on the ground. With rigorous testing at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, where the module was built, and Kennedy now complete, RRM3 will go into storage until final launch preparations are conducted later this fall.

The mission will launch aboard a SpaceX Commercial Resupply Services mission to the space station later this year. Once installed, the transfer and storage technologies will be put to the test.

The station’s Dextre robot will use a suite of three tools for the technology demonstration. The cryogen servicing tool delivers the cryogen transfer hose from a source tank filled with liquid methane to an empty receiving tank within the module. The multi-function tool operates adapters, or smaller specialized tools, for transferring liquid methane. The Visual Inspection Poseable Invertebrate Robot 2 (VIPIR2) is the eyes of the operation and uses a state-of-the-art robotic camera to verify the successful implementation of the tools used to complete the liquid methane transfers.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: cuddihy on 06/20/2018 09:39 pm
I thought IDA-3 was supposed to be on SpX-16. Has that shifted again?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: gongora on 06/20/2018 09:56 pm
I thought IDA-3 was supposed to be on SpX-16. Has that shifted again?

Apparently so.  Maybe we'll get a partial FPIP at the NASA Advisory Council meetings next month.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: russianhalo117 on 06/20/2018 11:34 pm
I thought IDA-3 was supposed to be on SpX-16. Has that shifted again?
IDA-3 was delayed due to the shift of Commercial Crew services to the right. Because of the shift Science payloads are given priority for now. IDA-3 will shift CRS flight by CRS flight until it services are needed.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Alexphysics on 06/20/2018 11:48 pm
IIRC, Kirk Shireman said on the last CRS mission that IDA-3 would go on the CRS-18 mission, he said at that time that he could be wrong about it so we "thought" he was wrong because the last FPIP showed IDA-3 going on the CRS-16 mission but now it seems he could have been right. CRS-18 is scheduled to launch inside the same period of time at when we should expect at least the first crewed mission to have happenned (around May-June 2019), so it makes sense.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Tomness on 06/21/2018 12:53 am
but now it seems he could have been right. CRS-18 is scheduled to launch inside the same period of time at when we should expect at least the first crewed mission to have happenned (around May-June 2019), so it makes sense.
That would be nice to line that up with comerical crew doing the installation of IDA-3 to free up USOS for science but that's so far out to line it up like that.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: gongora on 08/01/2018 07:23 pm
Article on infrared sensor demo that is part of the RRM3 mission.

Next-Generation Photodetector Camera to Deploy During Robotic Servicing Demonstration Mission (https://www.nasa.gov/feature/goddard/2018/next-generation-photodetector-camera-to-deploy-during-robotic-servicing-demonstration)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Mobius57 on 08/02/2018 07:29 am
I noticed the other day that we've never had a November launch :)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: gongora on 08/02/2018 02:25 pm
I noticed the other day that we've never had a November launch :)
shhhhh...don't jinx it
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: gongora on 08/31/2018 01:01 am
Quote
Iridium and NASA just learned that TechEdSat-8 has been added to the launch manifest for SpaceX-16, which is scheduled to be launched on December 1, 2018
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jbenton on 08/31/2018 02:28 am
I noticed the other day that we've never had a November launch :)
shhhhh...don't jinx it

Quote
Iridium and NASA just learned that TechEdSat-8 has been added to the launch manifest for SpaceX-16, which is scheduled to be launched on December 1, 2018

I guess Mobius jinxed it.  :P
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jbenton on 08/31/2018 02:33 am
Do we know which capsule is being launched for this mission? To my knowledge C112 and C113 have not yet been reused.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ZachS09 on 09/01/2018 03:24 am
Do we know which capsule is being launched for this mission? To my knowledge C112 and C113 have not yet been reused.

What about the Dragons prior to CRS-4 (C106) or C107 from CRS-5? Those have not been reused either.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Alexphysics on 09/01/2018 07:17 am
Dragons prior to CRS-4 were in bad conditions to be refurbished mainly because of salt water intrusion. They upgraded the capsules from CRS-8 onwards, they had more protection against salt water intrusion and those are easier and faster to refurbish. They will need to use three times a few Dragons to complete the CRS-1 contract.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vaporcobra on 09/17/2018 07:52 pm
Quote
Inside the Space Station Processing Facility high bay at NASA's Kennedy Space Center in Florida, technicians work on the pump package assembly (PPA) on Aug. 30, 2018. The payload will be carried to the International Space Station on SpaceX's 16th Commercial Resupply Services mission. The PPA will be used to continuously drive the cooling water in the space station's thermal control system. The assembly includes a centrifuge pump, a fine filter and gas trap for pump protection, a coarse outlet filter, sensors, and an accumulator. The PPA also will provide a reservoir used for makeup of coolant if leakage occurred. CRS-16 is scheduled to launch to the space station later this year. Photo credit: NASA/Glenn Benson

https://www.flickr.com/photos/nasakennedy/30873974548/in/dateposted/

(https://c2.staticflickr.com/2/1873/30873974548_3a12a48cd0_k.jpg)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Steven Pietrobon on 09/18/2018 12:56 pm
Does anyone know if the PPA is an internal or external payload?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: crandles57 on 09/18/2018 01:21 pm
Quote
CRS-16, on November 27 at the earliest

http://www.launchphotography.com/Delta_4_Atlas_5_Falcon_9_Launch_Viewing.html

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: AnalogMan on 09/18/2018 03:40 pm
Does anyone know if the PPA is an internal or external payload?

PPAs are installed inside the ISS, so I would think that it will be carried as an internal Dragon payload.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Olaf on 09/29/2018 02:55 pm
http://www.collectspace.com/ubb/Forum18/HTML/001448.html
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mazen hesham on 10/03/2018 10:49 am
Do you think this will be on a new or reused booster ?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ZachS09 on 10/03/2018 12:37 pm
Do you think this will be on a new or reused booster ?

As of right now, there aren't any sources saying whether a new or flight-proven booster will be used.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: speedevil on 10/11/2018 04:19 pm
Are there any obvious manifest changes for a mission likely to be in the window when Soyuz is still down?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: pb2000 on 10/11/2018 04:52 pm
Are there any obvious manifest changes for a mission likely to be in the window when Soyuz is still down?

More importantly is there any point in sending Dragon up to a station that may need to be abandoned a week later?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RonM on 10/11/2018 05:06 pm
Are there any obvious manifest changes for a mission likely to be in the window when Soyuz is still down?

More importantly is there any point in sending Dragon up to a station that may need to be abandoned a week later?

More like a month later. Why not stock up for future crews? Anyway, there are other options than leaving ISS without a crew. For example, send up the next Progress as a test. Even if there is still doubt after a successful Progress flight, send the next Soyuz without crew so the current crew can stay for another six months.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: scr00chy on 10/11/2018 06:33 pm
Are there any obvious manifest changes for a mission likely to be in the window when Soyuz is still down?

https://twitter.com/ChrisG_NSF/status/1050425498071789568
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Olaf on 10/21/2018 12:10 pm
https://twitter.com/NanoRacks/status/1052636703528296453
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Olaf on 10/22/2018 06:14 pm
It looks like SpX-16 is now in December.
https://twitter.com/TristanPrejean/status/1053366248590004224
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: russianhalo117 on 10/22/2018 06:26 pm
It looks like SpX-16 is now in December.
https://twitter.com/TristanPrejean/status/1053366248590004224
Has to because NG-10 will be berthed N1N and HTV-7 is currently N2N. Unless they relocate PMA3 to N3 or Z1 there is no room until HTV-7 leaves.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: gongora on 10/22/2018 08:37 pm
Has to because NG-10 will be berthed N1N and HTV-7 is currently N2N. Unless they relocate PMA3 to N3 or Z1 there is no room until HTV-7 leaves.

Couldn't HTV-7 leave before Nov. 27?  Its planned duration was just under 2 months.  (I really wouldn't be surprised if CRS-16 slipped a little, just not sure that HTV-7 would be the reason.)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Alexphysics on 10/22/2018 08:49 pm
Has to because NG-10 will be berthed N1N and HTV-7 is currently N2N. Unless they relocate PMA3 to N3 or Z1 there is no room until HTV-7 leaves.

Couldn't HTV-7 leave before Nov. 27?  Its planned duration was just under 2 months.  (I really wouldn't be surprised if CRS-16 slipped a little, just not sure that HTV-7 would be the reason.)

They have to change the batteries on the solar panels so they need HTV-7 at the station for that. However, they also need more people trained on EVA's to do them, so maybe HTV-7 will stay longer until Soyuz MS-11 flies to the ISS. I would just unberth HTV-7 and let it free fly for a month or two until CRS-16 has left the station... but obviously I'm not the one making decisions and I could totally be wrong.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: zubenelgenubi on 10/23/2018 02:22 am
Has to because NG-10 will be berthed N1N and HTV-7 is currently N2N. Unless they relocate PMA3 to N3 or Z1 there is no room until HTV-7 leaves.

Couldn't HTV-7 leave before Nov. 27?  Its planned duration was just under 2 months.  (I really wouldn't be surprised if CRS-16 slipped a little, just not sure that HTV-7 would be the reason.)

They have to change the batteries on the solar panels so they need HTV-7 at the station for that. However, they also need more people trained on EVA's to do them, so maybe HTV-7 will stay longer until Soyuz MS-11 flies to the ISS. I would just unberth HTV-7 and let it free fly for a month or two until CRS-16 has left the station... but obviously I'm not the one making decisions and I could totally be wrong.

I had the same question about HTV departing and "station-keeping" with the ISS until after the battery replacement EVA's were completed, then returning and berthing so the replaced batteries could be stowed externally.

I cross-posted in the US EVA-52 and HTV-7 threads.

I hadn't gotten an answer yet.
***

New article
SpaceX lines up five launches to close out 2018 (https://www.nasaspaceflight.com/2018/10/spacex-lines-five-launches-2018/), October 22, by Michael Baylor
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Olaf on 10/23/2018 04:56 am
There was an information by anik in the NK forum about the possibility, that HTV-7 will leave the ISS when the US EVAs are performed.
Google translation
Quote
If I understand correctly, in the case of the US exits in December, the HTV-7 should leave after them.
http://novosti-kosmonavtiki.ru/forum/messages/forum10/topic12565/message1808190/#message1808190
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: russianhalo117 on 10/23/2018 06:42 am
Has to because NG-10 will be berthed N1N and HTV-7 is currently N2N. Unless they relocate PMA3 to N3 or Z1 there is no room until HTV-7 leaves.

Couldn't HTV-7 leave before Nov. 27?  Its planned duration was just under 2 months.  (I really wouldn't be surprised if CRS-16 slipped a little, just not sure that HTV-7 would be the reason.)

They have to change the batteries on the solar panels so they need HTV-7 at the station for that. However, they also need more people trained on EVA's to do them, so maybe HTV-7 will stay longer until Soyuz MS-11 flies to the ISS. I would just unberth HTV-7 and let it free fly for a month or two until CRS-16 has left the station... but obviously I'm not the one making decisions and I could totally be wrong.
Certified solo flight of 5 days docked, 45 days and stand by 7 days. Contingency loitering capability is unknown but I do recall that HTV onboard battery lifetime was a contributing factor in the numbers above.
https://directory.eoportal.org/web/eoportal/satellite-missions/h/htv-7
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: zubenelgenubi on 10/24/2018 01:48 am
Cross-post re: delay of launch to December:
Quote

Falcon 9 from pad 40 will launch the next Dragon resupply mission to the ISS, CRS-16, on December
at the earliest.
http://www.launchphotography.com/Delta_4_Atlas_5_Falcon_9_Launch_Viewing.html
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Olaf on 10/24/2018 06:56 am
There was an information by anik in the NK forum about the possibility, that HTV-7 will leave the ISS when the US EVAs are performed.
Google translation
Quote
If I understand correctly, in the case of the US exits in December, the HTV-7 should leave after them.
http://novosti-kosmonavtiki.ru/forum/messages/forum10/topic12565/message1808190/#message1808190
The above information is not correct.
https://blogs.nasa.gov/spacestation/2018/10/23/station-preps-for-japan-us-ship-operations-next-month/
Quote
The packed HTV-7 is due to be removed from the Harmony module with the Canadarm2 and released back into Earth orbit in November.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Olaf on 10/29/2018 01:04 pm
Quote
Iridium and NASA just learned that TechEdSat-8 has been added to the launch manifest for SpaceX-16, which is scheduled to be launched on December 1, 2018
The question is now, only TechEdSat-8 or all ELaNa-21 satellites?
Are there any news to this topic?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jacqmans on 10/31/2018 02:10 pm
October 31, 2018
MEDIA ADVISORY M18-161

NASA Invites Media to 16th SpaceX Cargo Launch to Space Station
 
Media accreditation now is open for the targeted Dec. 4 SpaceX launch from Space Launch Complex 40 at Cape Canaveral Air Force Station (CCAFS) in Florida to deliver supplies, equipment and science investigations to the International Space Station.

A SpaceX Dragon cargo spacecraft is planned to launch on a Falcon 9 rocket at 1:38 p.m. EST on the company’s 16th Commercial Resupply Services contract mission. Media prelaunch and launch activities will take place at NASA’s Kennedy Space Center and neighboring CCAFS.

Media accreditation deadlines are as follows:

•   International media without U.S. citizenship must apply by 4:30 p.m. Sunday, Nov. 4, for access to Cape Canaveral Air Force Station, or by 4:30 p.m. Tuesday, Nov. 20, for access to Kennedy media activities only.
•   U.S. media must apply by 4:30 p.m. Tuesday, Nov. 27.

All accreditation requests should be submitted online at:
https://media.ksc.nasa.gov

For questions about accreditation, please email [email protected] For other questions, contact Kennedy’s newsroom at 321-867-2468.

The International Space Station is a convergence of science, technology and human innovation that demonstrates new technologies and enables research not possible on Earth. The space station has been occupied continuously since November 2000. In that time, more than 230 people and a variety of international and commercial spacecraft have visited the orbiting laboratory. The space station remains the springboard to NASA's next great leap in exploration, including future missions to the Moon and eventually to Mars.

For launch countdown coverage, NASA's launch blog, and more information about the mission, visit:
https://www.nasa.gov/spacex
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Chris Bergin on 10/31/2018 02:12 pm
Updated the thread title due to the above.

https://twitter.com/NASASpaceflight/status/1057651378523435013
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vaporcobra on 11/07/2018 02:58 am
Robotic Refueling Mission-3 (RRM3) was moved into SpaceX's processing facility on Oct 30.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Norm38 on 11/16/2018 12:27 am
Since B1046.3 is now confirmed for SSO-A, I hope this flight is getting B1048.3.
Back to back 3rd flights would be cool.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Watchdog on 11/19/2018 07:23 pm
According to this source: https://www.reddit.com/r/spacex/wiki/cores
the Falcon 9 core 1050 is now assigned to CRS SpX-16
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Targeteer on 11/23/2018 08:59 pm
November 23, 2018
MEDIA ADVISORY M18-178
NASA Highlights Science on Next Resupply Mission to International Space Station

NASA will host a media teleconference at 1 p.m. EST Wednesday, Nov. 28, to discuss select science investigations launching on the next SpaceX commercial resupply flight to the International Space Station.

SpaceX is targeting Dec. 4 for launch of its Dragon spacecraft on a Falcon 9 rocket from Space Launch Complex 40 at Cape Canaveral Air Force Station (CCAFS) in Florida.

Participants in the briefing will be:

    Hsiao Smith, deputy director for technical of the Satellite Servicing Projects Division at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, will discuss the Robotic Refueling Mission-3 to demonstrate the storage and transfer of liquid methane in space for the first time.
    Timothy Etheridge, principal investigator for the Molecular Muscle investigation, and a professor at University of Exeter, Department of Sport and Health Sciences in the United Kingdom,will discuss research to examine the molecular causes of muscle abnormalities during spaceflight in order to establish effective countermeasures.
    Ralph Dubayah, principal investigator for Global Ecosystem Dynamics Investigation (GEDI) at the Joint Global Carbon Cycle Center in College Park, Maryland, will discuss an investigation to test high-quality laser ranging observations of the Earth’s forests and topography required to advance the understanding of important carbon and water cycling processes, biodiversity, and habitat.
    Vic Keasler, Director of Research, Development and Engineering at Nalco Champion, an Ecolab company, will discuss an investigation to examine the rate of corrosion on carbon steel materials caused by films made up of microorganisms on Earth and in space.
    Jahaun Azadmanesh, a doctoral student at the University of Nebraska Medical Center in Omaha, Nebraska, will discuss the Perfect Crystals investigation which aims to help understand how an antioxidant protein helps protect the human body from oxidizing radiation and oxidants created as a byproduct of metabolism.

To participate in the teleconference, media must contact Kathryn Hambleton at 202-358-1100 or [email protected] by 5 p.m. Tuesday, Nov 27, for dial-in information.

Audio of the teleconference will be streamed live online at:

https://www.nasa.gov/nasalive

SpaceX’s Dragon spacecraft will carry crew supplies, scientific research and hardware to the orbiting laboratory to support the Expedition 57 and 58 crews for the 16th contracted mission by SpaceX under NASA’s Commercial Resupply Services contract.

For launch countdown coverage, NASA's launch blog, and more information about the mission, visit:

https://www.nasa.gov/spacex
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: input~2 on 11/25/2018 02:21 pm
F3192/18 -  ROCKET LAUNCH WILL TAKE PLACE FLW RECEIVED FROM GOVERNMENT OF UNITED STATES OF AMERICA: HAZARDOUS OPS WILL BE CONDUCTED FOR ATMOSPHERIC RE-ENTRY AND SPLASHDOWN OF LAUNCH VEHICLE FALCON-9 CRS-16 AND PARTICIPATING SUPPORT ACFT WI THE FOLLOWING AREAS: S33 49 E90 53 S31 31 E92 20 S43 04 E115 08 S48 44 E138 14 S50 11 E163 00 S52 56 E163 00 S53 56 E157 53 S53 37 E135 38 S48 02 E111 41 S38 29 E96 28 TO BEGINNING. SFC - UNL, PRI RE-ENTRY 04 1910-1952 BACKUP RE-ENTRY 05 1847-1929, 04 DEC 19:10 2018 UNTIL 05 DEC 19:29 2018. CREATED: 22 NOV 00:49 2018
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: FutureSpaceTourist on 11/26/2018 08:38 pm
https://twitter.com/EmreKelly/status/1067167549232693248
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Chris Bergin on 11/27/2018 01:23 pm
L2 Range has the Static Fire test NET today (for the confirmed launch date NET), but plenty of time until the launch date, so could be later in the week. Anyway, booster spotting will confirm status, so we'll appreciate any note of rollout, vertical on the pad today or later this week.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Chris Bergin on 11/27/2018 07:02 pm
SF is later in the week now.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rondaz on 11/27/2018 11:58 pm
Dragon Set to Deliver Supplies to International Space Station

Bob Granath Posted on November 27, 2018

Commercial Resupply Services Mission: SpaceX CRS-16
Launch: 1:38 p.m. EST, Tuesday, Dec. 4, 2018
Lift Off: Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida
Launch Vehicle: SpaceX Falcon 9, 230 feet-tall
Spacecraft: Dragon, 20 feet high, 12 feet-in diameter
Payload: Dragon will deliver supplies and payloads, including materials to directly support dozens of the science and research investigations that will occur during the space station’s Expeditions 57 and 58.
Return to Earth: After about one month attached to the space station, Dragon will return with results of earlier experiments, splashing down in the Pacific Ocean off the coast of Baja California.
Payloads on Board: Includes the Robotic Refueling Mission 3, or RRM3, and the Global Ecosystem Dynamics Investigation lidar, or GEDI.

https://blogs.nasa.gov/kennedy/2018/11/27/dragon-set-to-deliver-supplies-to-international-space-station-5/
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rondaz on 11/28/2018 12:00 am
ISS Daily Summary Report – 11/26/2018

SpaceX-16 (SpX-16) Dragon Pre-Pack:  In preparation for SpX-16 Dragon launch planned for December 4 and arrival to ISS on December 6, the crew started to pack items that will be returning to the ground. 
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Raul on 11/28/2018 02:25 pm
SpaceX Mission 1404 CRS-16 Launch Hazard Areas Map (https://www.google.com/maps/d/viewer?mid=1dHqAYXF6NNKkdcnXTcHE0123pBKHoxh_&ll=30.08028635401825%2C-79.50639734132909&z=7) based on issued NOTMAR/NOTAMs.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: bman549 on 11/28/2018 02:47 pm
The picture shows CCAFS but the link shows VAFB
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rondaz on 11/28/2018 02:51 pm
ISS Daily Summary Report – 11/27/2018

SpaceX 16 (SpX-16) Dragon On-Board Training (OBT): The crew reviewed Dragon Robotics procedures and participated in a conference with ground specialists in support of SpX-16 Dragon arrival. Using computer based training, the crew reviewed the Dragon mission profile, rendezvous crew procedures, and the crew interfaces for monitoring and commanding Dragon. SpX-16 Dragon launch is currently scheduled for December 4 with capture and berthing planned for December 6.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: envy887 on 11/28/2018 07:10 pm
SpaceX Mission 1404 CRS-16 Launch Hazard Areas Map (https://www.google.com/maps/d/viewer?mid=1dHqAYXF6NNKkdcnXTcHE0123pBKHoxh_&ll=30.08028635401825%2C-79.50639734132909&z=7) based on issued NOTMAR/NOTAMs.

What's the downrange hazard area for? Dragon nosecone and panel fairings?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: SMS on 11/28/2018 09:18 pm
https://twitter.com/flatoday_jdean/status/1067869131075129345
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Targeteer on 11/28/2018 09:22 pm
November 28, 2018
MEDIA ADVISORY M18-179

NASA commercial cargo provider SpaceX is targeting 1:38 p.m. EST Tuesday, Dec. 4, for the launch of its 16th resupply mission to the International Space Station. Live coverage will begin on NASA Television and the agency’s website Monday, Dec. 3, with prelaunch events.

The Dragon spacecraft will carry supplies and payloads, including critical materials to directly support dozens of the more than 250 science and research investigations that will worked by the space station’s Expeditions 57 and 58 crews.

Among the research it will bring to station, the Dragon’s unpressurized trunk is carrying the Robotic Refueling Mission-3 (RRM3) and the Global Ecosystem Dynamics Investigation (GEDI). RRM3 demonstrates the storage and transfer of cryogenic fluid, which is critical for propulsion and life support systems in space. While the Robotic Refueling Mission Phase 2 (RRM2) demonstrated tasks leading up to coolant replenishment, the actual transfer of cryogenic fluid in orbit will be carried out for the first time with RRM3, using liquid methane. GEDI will make high-quality laser ranging observations of Earth’s forests and topography required to advance the understanding of important carbon and water cycling processes, biodiversity and habitat. Mounted on the Japanese Experiment Module's Exposed Facility, GEDI will provide the first high-resolution observations of forest vertical structure at a global scale.

Dragon will reach its preliminary orbit about 10 minutes after launch. It will then deploy its solar arrays and begin a carefully choreographed series of thruster firings to reach the orbiting laboratory two days later on Thursday, Dec. 6. When it arrives, Expedition 57 Commander Alexander Gerst of ESA (European Space Agency) and Flight Engineer Serena Auñón-Chancellor of NASA will grapple Dragon. Anne McClain of NASA will assist the duo by monitoring telemetry during Dragon’s approach. After Dragon’s capture, ground controllers will send commands from mission control in Houston for the station’s arm to rotate and install the spacecraft on the bottom of the station’s Harmony module.

Full mission coverage is as follows. All times are EST:

Monday, Dec. 3

    9:30 a.m. – What’s on Board science briefing from NASA’s Kennedy Space Center in Florida. The briefing will highlight the following research:
        Jill McGuire, project manager, NASA’s Goddard Space Flight Center in Greenbelt, Maryland, will discuss RRM3.
        Dr. Ralph Dubayah, principal investigator, University of Maryland, and Bryan Blair, deputy principal investigator, Goddard, will discuss GEDI.   
        Dr. Elaine Horn-Ranney, principal investigator, Tympanogen, will discuss an investigation into novel wound dressings and how antibiotics can be directly released on wound sites.
        Nicole Wagner, LambdaVision, will discuss the Enhancement of Performance and Longevity of a Protein-Based Retinal Implant.
        Winners of the Marvel Guardians of the Galaxy Space Station Challenge:
            Adia Bulawa, project lead, Staying Healthy in Space
            Sarina Kopf, project lead, Aeroponic Farming in Microgravity

    3:30 p.m. – Prelaunch News Conference from Kennedy with the following representatives:
        Joel Montelbano, deputy ISS program manager, NASA’s Johnson Space Center
        Hans Koenigsmann, vice president of Build and Flight Reliability at SpaceX
        Kirt Costello, ISS program chief scientist, Johnson
        Clay Flinn, launch weather officer

Tuesday, Dec. 4

    1 p.m. – Launch coverage begins for the 1:38 p.m. launch
    3:30 p.m. – Postlaunch news conference at Kennedy, with the following representatives:
        Joel Montelbano, deputy ISS program manager, NASA’s Johnson Space Center
        Hans Koenigsmann, vice president of Build and Flight Reliability at SpaceX

Thursday, Dec. 6

    4:30 a.m. – Dragon rendezvous, grapple and berthing to the space station. Capture is scheduled for approximately 6 a.m.
    7:30 a.m. – Dragon installation to the nadir port of the station’s Harmony module

The Dragon spacecraft will spend about five weeks attached to the space station. Dragon will remain at the orbital outpost until Jan. 13, when the spacecraft will return to Earth with research and return cargo.

The deadline for media to apply for accreditation for this launch has passed, but more information about media accreditation is available by emailing [email protected]

For the latest schedule of prelaunch briefings, events and NASA TV coverage, visit:

https://www.nasa.gov/content/spacex-crs-16-briefings-and-events/

Learn more about the SpaceX resupply mission to the International Space Station at:

https://www.nasa.gov/spacex
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Raul on 11/29/2018 07:07 am
SpaceX Mission 1404 CRS-16 Launch Hazard Areas Map (https://www.google.com/maps/d/viewer?mid=1dHqAYXF6NNKkdcnXTcHE0123pBKHoxh_&ll=30.08028635401825%2C-79.50639734132909&z=7) based on issued NOTMAR/NOTAMs.
What's the downrange hazard area for? Dragon nosecone and panel fairings?

Launch Hazard Area A (green) is drop area in case of launch failure typically up to Max Q or in case of booster entry-landing failure.

Launch Hazard Area B (orange) is drop area in case of booster boostback failure, in case S2 ignition failure or for Dragon nosecone.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Raul on 11/29/2018 07:10 am
SpaceX CRS-16 Mission Overview:
Quote
Total Cargo:   5,673 pounds / 2,573 kilograms
Total Pressurized Cargo with Packaging:   3,523 pounds / 1,598 kilograms
Unpressurized Payloads:   2,150 pounds / 975 kilograms
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Chris Bergin on 11/29/2018 05:21 pm
Static Fire on for later today. L2 had Thursday PM, so this is all following that now.

https://twitter.com/Cygnusx112/status/1068207102827642881
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: FutureSpaceTourist on 11/29/2018 08:20 pm
https://youtu.be/jwubeBg8p2A
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: FutureSpaceTourist on 11/30/2018 04:24 pm
Sounds like a scrub on yesterday’s static fire attempt:

https://twitter.com/uslaunchreport/status/1068553141036244994
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: FutureSpaceTourist on 11/30/2018 04:26 pm
https://twitter.com/cygnusx112/status/1068554965000568832
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jacqmans on 11/30/2018 05:24 pm
November 30, 2018 
MEDIA ADVISORY 018-18
Kennedy Space Center Traffic and Road Closures for Upcoming Launch Activities

Heavy traffic on and around the Kennedy Space Center and the Kennedy Space Center Visitor Complex is expected Tuesday, Dec. 4, due to center activities surrounding the upcoming launch of SpaceX Falcon 9 rocket from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida. Liftoff is planned for no earlier than 1:38 p.m. EST on Tuesday, Dec. 4.

PUBLIC ACCESS ROAD CLOSURES

Starting at 9 a.m. EST on Tuesday, Dec. 4, Kennedy Space Center will be enforcing restricted access from its boundary lines to the center for the duration of the SpaceX launch attempt.    

State Road 3 from the Gate 2 News Media Pass and Identification Building to State Road 405 (NASA Causeway), including Space Commerce Way, will be closed to the general public at 9 a.m. Access to Kennedy Space Center, the Kennedy Space Center Visitor Complex, Exploration Park and Blue Origin will be limited to authorized personnel. The roads will reopen after launch.

The NASA Causeway between US1 and Gate 3 will also be restricted to authorized personnel (badged employees and their partners). The roads will reopen after launch.

The Kennedy Space Center Visitor Complex will be open; however, once capacity has been reached, no further traffic will be permitted.

The A. Max Brewer Bridge on State Road 406 in Titusville, east to Playalinda Beach will be open to all motor vehicle traffic until capacity is reached or noon, whichever comes first.

State Road 3 North at US1 in Volusia County, south to Playalinda Beach will be open to all motor vehicle traffic until capacity is reached or noon, whichever comes first.

Please expect delays and plan accordingly.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rondaz on 11/30/2018 07:40 pm
Science Briefing, Prelaunch News Conference Set for SpaceX CRS-16

Linda Herridge Posted on November 30, 2018

SpaceX’s 16th commercial resupply mission to the International Space Station for NASA is targeted to launch at 1:39 p.m. EST Tuesday, Dec. 4, from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida. Join us Monday, Dec. 3, as we start SpaceX CRS-16 launch week coverage with prelaunch events on NASA Television and the agency’s website.

9:30 a.m. – What’s on Board science briefing from NASA’s Kennedy Space Center in Florida. The briefing will highlight the following research:

Jill McGuire, project manager, NASA’s Goddard Space Flight Center in Greenbelt, Maryland, will discuss RRM3.

Dr. Ralph Dubayah, principal investigator, University of Maryland, and Bryan Blair, deputy principal investigator, Goddard, will discuss GEDI.

Dr. Elaine Horn-Ranney, principal investigator, Tympanogen, will discuss an investigation into novel wound dressings and how antibiotics can be directly released on wound sites.

Nicole Wagner, LambdaVision, will discuss the Enhancement of Performance and Longevity of a Protein-Based Retinal Implant.

Winners of the Marvel Guardians of the Galaxy Space Station Challenge:

Adia Bulawa, project lead, Staying Healthy in Space

Sarina Kopf, project lead, Aeroponic Farming in Microgravity

3:30 p.m. – Prelaunch News Conference from Kennedy with the following representatives:

Joel Montelbano, deputy ISS program manager, NASA’s Johnson Space Center

Hans Koenigsmann, vice president of Build and Flight Reliability at SpaceX

Kirt Costello, ISS program chief scientist, Johnson

Clay Flinn, launch weather officer

For the latest schedule of prelaunch briefings, events and NASA TV coverage, visit: https://www.nasa.gov/content/spacex-crs-16-briefings-and-events/

Learn more about the SpaceX resupply mission to the International Space Station at: https://www.nasa.gov/spacex

https://blogs.nasa.gov/spacex/2018/11/30/science-briefing-prelaunch-news-conference-set-for-spacex-crs-16/
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: MattBaker on 12/01/2018 01:39 am
Sounds like a scrub on yesterday’s static fire attempt

Weird, 2nd static fire in a row with a scrub. Are they trying a new procedure or does anyone remember static fire delays with the Block 5 other than the one in Vandenberg last week?

I guess static fire delays are the definition of "better safe than sorry" but I'd hope those two points don't become a pattern.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Alexphysics on 12/01/2018 01:52 am
Sounds like a scrub on yesterday’s static fire attempt

Weird, 2nd static fire in a row with a scrub. Are they trying a new procedure or does anyone remember static fire delays with the Block 5 other than the one in Vandenberg last week?

I guess static fire delays are the definition of "better safe than sorry" but I'd hope those two points don't become a pattern.

To be more precise, this is not the second in a row but the second in the last three static fires. SSO-A static fire went ok.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: MattBaker on 12/01/2018 02:03 am
Sorry, mixed up SSO-A and Es'hail-2.

Too many darn launches.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Michael Baylor on 12/01/2018 02:26 am
Static fire!
https://twitter.com/cbs_spacenews/status/1068707707547516933
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Chris Bergin on 12/01/2018 02:59 am
Good quick look review. Will copy some of this over and make the update thread:
https://twitter.com/SpaceX/status/1068715609397940224
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mvpel on 12/02/2018 08:18 pm
Does anyone know of a site which could be used to determine launch visibility with respect to the launch’s trajectory and a given location? I’ll be in Grand Turk for this launch, and naturally had been hoping for a southeastern trajectory, and so I’m wondering if any phase of the flight might be visible from a vantage point that far southeast.


Sent from my iPhone using Tapatalk
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Alexphysics on 12/02/2018 10:31 pm
Does anyone know of a site which could be used to determine launch visibility with respect to the launch’s trajectory and a given location? I’ll be in Grand Turk for this launch, and naturally had been hoping for a southeastern trajectory, and so I’m wondering if any phase of the flight might be visible from a vantage point that far southeast.


Sent from my iPhone using Tapatalk

Try Flight Club, that may help
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jarnis on 12/03/2018 11:09 am
Does anyone know of a site which could be used to determine launch visibility with respect to the launch’s trajectory and a given location? I’ll be in Grand Turk for this launch, and naturally had been hoping for a southeastern trajectory, and so I’m wondering if any phase of the flight might be visible from a vantage point that far southeast.


Sent from my iPhone using Tapatalk

It is going to launch northeast, so probably nope.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rondaz on 12/04/2018 05:02 am
SpaceX CRS-16 Now Targeted for Dec. 5

Stephanie Martin Posted on December 3, 2018

NASA and SpaceX are now targeting Wednesday, Dec. 5 for launch of the 16th SpaceX cargo resupply mission to the International Space Station. The launch was moved to Wednesday after mold was found on food bars for a rodent investigation prior to handover to SpaceX. Teams will use the extra day to replace the food bars. The launch time for Wednesday is 1:16 p.m. EST.

https://blogs.nasa.gov/kennedy/2018/12/03/spacex-crs-16-now-targeted-for-dec-5/
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: dnavas on 12/04/2018 05:11 am
The mouse caterers

https://flightaware.com/live/flight/N777ZL

For those that might read the above after the link content disappears:
Takeoff (SJC)  05:27PM PST  Scheduled 04:30PM PST
Landing  12:55AM EST (+1)  Scheduled 12:01AM EST (+1)

So, it was an hour late; as they were already over time, it makes the slip seem inevitable.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: SimonFD on 12/04/2018 10:08 am
SpaceX CRS-16 Now Targeted for Dec. 5

Stephanie Martin Posted on December 3, 2018

NASA and SpaceX are now targeting Wednesday, Dec. 5 for launch of the 16th SpaceX cargo resupply mission to the International Space Station. The launch was moved to Wednesday after mold was found on food bars for a rodent investigation prior to handover to SpaceX. Teams will use the extra day to replace the food bars. The launch time for Wednesday is 1:16 p.m. EST.

https://blogs.nasa.gov/kennedy/2018/12/03/spacex-crs-16-now-targeted-for-dec-5/

Bold mine. What a weird statement seeing as it was the food bars causing the delay in the first place. The wording they use makes it sound like they're taking advantage of a delay caused by something else! Or is it just me?
 :o
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Semmel on 12/04/2018 10:32 am
SpaceX CRS-16 Now Targeted for Dec. 5

Stephanie Martin Posted on December 3, 2018

NASA and SpaceX are now targeting Wednesday, Dec. 5 for launch of the 16th SpaceX cargo resupply mission to the International Space Station. The launch was moved to Wednesday after mold was found on food bars for a rodent investigation prior to handover to SpaceX. Teams will use the extra day to replace the food bars. The launch time for Wednesday is 1:16 p.m. EST.

https://blogs.nasa.gov/kennedy/2018/12/03/spacex-crs-16-now-targeted-for-dec-5/

Bold mine. What a weird statement seeing as it was the food bars causing the delay in the first place. The wording they use makes it sound like they're taking advantage of a delay caused by something else! Or is it just me?
 :o

From the press conference yesterday it was pretty clear that the food bars caused the delay. Yesterday they were not clear if they need to delay or not not surprised at all.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jacqmans on 12/04/2018 10:55 am
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ChrisC on 12/05/2018 01:30 am
I am really disappointed that NASA *still* hasn't gotten around to posting the two CRS-16 news conferences to Youtube, 30 hours after they happened.  Pre-launch news conference: nope.  Science / what's-on-board news conference: nope.  (Note: the 5 minute teaser is not the news conference.)

Alas, John44's videos are erroring out for me, so can't rely on that as backup.

Just had to grumble, I guess.

EDIT: oh, I just thought of another method, the Ustream auto-archive!  The link below provides both of the news conferences.  First is the What's On Board briefing, and then (at 1h30m) is the Pre-Launch briefing: http://www.ustream.tv/recorded/118527221

Ustream videos are more difficult to watch than Youtube (YT really has their tech together) but I'll take it.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ChrisC on 12/05/2018 01:45 am
And now that I can actually see the presser ...

In the Whats-On-Board presentation, Kirt Costello was billed as the ISS Chief Scientist.  Previously he was deputy, under Julie Robinson.  What happened to Julie?  Google has failed to tell me.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: flyright on 12/05/2018 04:56 pm
On the NASA Webcast, NASA commentator Joshua Santora is reporting from the "Mission Director Center".
What is the "Mission Director Center"?
Is this the SpaceX Launch Control Center?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Halidon on 12/05/2018 05:24 pm
uh oh, losing stage 1
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ellindsey on 12/05/2018 05:24 pm
Some pretty wild gyrations there.  I don't think they're getting this Stage 1 back.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Prettz on 12/05/2018 05:25 pm
Holy moley, what happened? Looked like the grid fins weren't moving
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Tass on 12/05/2018 05:26 pm
Made a "water landing"
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jak Kennedy on 12/05/2018 05:26 pm
In the drink
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: toruonu on 12/05/2018 05:27 pm
But why cut the feed? :)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: matthewkantar on 12/05/2018 05:27 pm
In one piece?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Norm38 on 12/05/2018 05:28 pm
Crazy, that's the first failed landing since June of 2016.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Tass on 12/05/2018 05:28 pm
In one piece?

Apparently so.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/05/2018 05:28 pm
how does a stage recover from such gyrations even?

suppose one control surface failed, and then the system recognized and adapted and .. still... the starting conditions were insane...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: chrisking0997 on 12/05/2018 05:29 pm
bet theres gonna be some good footage of that
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OnWithTheShow on 12/05/2018 05:29 pm
Am I the only one envisioning this....
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: matthewkantar on 12/05/2018 05:29 pm
Will be lots of video of the crash, stage was very close to the Cape. Cheering was because the stage didn't take out anything on land.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: AC in NC on 12/05/2018 05:29 pm
That didn't look like ice that came off during descent.  It looked like some kind of seal was lost from a grid fin.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kevinof on 12/05/2018 05:30 pm
Never saw the fins move once deployed.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/05/2018 05:30 pm
I noticed on this and the previous flight that the N2 thrusters seem more active after the grid fins come out than on previous flights.  I wonder if this is related to the "water landing" (AKA, kaboom).

Whether SpaceX chooses to release it or not there should be plenty of video coming out.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jaredgalen on 12/05/2018 05:30 pm
In a way a failure is good, something to improve upon... 🤔
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: rower2000 on 12/05/2018 05:30 pm
Holy moley, what happened? Looked like the grid fins weren't moving
Stuck fin or stuck thruster? Looked like the fins did nothing for one or two seconds, and then wild and intense corrections...

But leave it to SpaceX. They did not have a crash, but a water landing, so with that wording I suppose it was soft and upright. If that's true, I'm amazed they could pull it out of that roll...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: matthewkantar on 12/05/2018 05:31 pm
I thought the grid fins were working pretty hard.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: AnnK on 12/05/2018 05:31 pm
But why cut the feed? :)
But why cut the feed? :)

Am sure the 1st stage went out of control and crashed. Space X does not share bad news
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: WithCarbos on 12/05/2018 05:32 pm
https://clips.twitch.tv/AdventurousConcernedGazelleKappaWealth (https://clips.twitch.tv/AdventurousConcernedGazelleKappaWealth)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Prettz on 12/05/2018 05:32 pm
how does a stage recover from such gyrations even?

suppose one control surface failed, and then the system recognized and adapted and .. still... the starting conditions were insane...
Really good software!
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: TrevorMonty on 12/05/2018 05:32 pm
Expect the odd failure it is first generation RLV. At least they have complete stage to analysis for fault, assuming it can be recovered.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OnWithTheShow on 12/05/2018 05:32 pm
It looked to me like there was more spin on the first stage all the way from stage sep. Maybe there was a non-functional thruster block
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jpo234 on 12/05/2018 05:33 pm
Something got loose at T+6:02.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 05:33 pm
But why cut the feed? :)
But why cut the feed? :)

Am sure the 1st stage went out of control and crashed. Space X does not share bad news

Don't worry, we'll see it. Lots of tracking cameras (professional and amateur) at KSC. :)

It definitely seemed like this was a gridfin issue.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Zach Swena on 12/05/2018 05:33 pm
It looked like either a control system failure, or actuator failure on the grid fins.  The top right fin in the picture seemed to be providing rotational input independently of the other fins, so I would think something wrong with the actuators, or position sensors causing a control system failure.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: deruch on 12/05/2018 05:33 pm
Even during the post-separation and boost-back portion of the return it looked squirlier than normal.  I'm not used to seeing fast rolls during that portion. 
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jak Kennedy on 12/05/2018 05:34 pm
That didn't look like ice that came off during descent.  It looked like some kind of seal was lost from a grid fin.

It was definitely circular.

edit for clarity.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: rockets4life97 on 12/05/2018 05:34 pm
No explosion in the video posted above on landing. That is impressive.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 05:34 pm
That didn't look like ice that came off during descent.  It looked like some kind of seal was lost from a grid fin.

It definitely circular.

It was just ice.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Halidon on 12/05/2018 05:34 pm
I thought the grid fins were working pretty hard.
Just re-wound the YouTube feed, seems like about 15 seconds before they cut away. The fins barely move after the entry burn, the fin on the left of the camera shot appears to not move at all and the one on the right moves just as the "spin" begins.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/05/2018 05:34 pm
"Water landing"

I really wish the director of the webcast had the guts to show that.

Anything from the NASA webcast?

Pictures / videos from anyone there??
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: envy887 on 12/05/2018 05:35 pm
Crazy, that's the first failed landing since June of 2016.

The Heavy core also splashed this year
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jcliving on 12/05/2018 05:35 pm
Wow!  I cannot believe they had the control they did!
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 05:35 pm
"Water landing"

I really wish the director of the webcast had the guts to show that.

Anything from the NASA webcast?

Pictures / videos from anyone there??

Chill, there will be plenty of video uploaded real soon... probably as I type. :)

EDIT: here is a still photo before impact: https://www.instagram.com/p/BrBAqubgxAf/  The landing burn certainly worked. :)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/05/2018 05:36 pm
Things went south ~5 seconds before the "stage 1 transonic" callout.  Could it have something to do with that?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: sghill on 12/05/2018 05:37 pm
At T+ 7:00, the booster looked like the angle was way way way off the end of the landing burn compared to previous landings (perhaps one outboard engine didn't shut down in time?). Then, at T+ 7:33, one of the gridfins was cranked all the way over and the other wasn't moving much at all as the spinning started.

It's easier to see both events if you watch the video, but here are two screen grabs.

I doubt we'll see more land touchdowns any time soon after this....

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: DigitalMan on 12/05/2018 05:37 pm
From those videos I would think it was at least possible to land intact but perhaps there was not enough control to safely vector over to the landing pad.

The way it was tilting and rotating perhaps the legs would have given out anyhow.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: matthewkantar on 12/05/2018 05:37 pm
Last words from the SpaceX launch host before the stage diverged: "It is SO exciting along the Space Coast!"
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CraigLieb on 12/05/2018 05:37 pm
Phone screen cap and magnified
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: chrisking0997 on 12/05/2018 05:37 pm
impressed that it recovered as well as it did.  it stood so long Id have to think it would have survived if it had made the LZ
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ellindsey on 12/05/2018 05:37 pm
There's already amateur footage of the landing attempt online.  It looks like one of the grid fins went hardover and got stuck.  Amazingly, the rocket managed to neutralize the roll and perform a soft touchdown anyway, but as it was on water it fell over and ruptured after touching down.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/05/2018 05:38 pm
https://clips.twitch.tv/AdventurousConcernedGazelleKappaWealth (https://clips.twitch.tv/AdventurousConcernedGazelleKappaWealth)

That's what I was hoping for. Amazing video!!!!
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: bbell99 on 12/05/2018 05:38 pm

Elon Musk twitter

‏Grid fin hydraulic pump stalled, so Falcon landed just out to sea. Appears to be undamaged & is transmitting data. Recovery ship dispatched.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kevinof on 12/05/2018 05:38 pm
https://twitter.com/elonmusk/status/1070386062164283392
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 05:38 pm
At T+ 7:00, the booster looked like the angle was way off the end of the landing burn. Then, at T+ 7:33, one of the gridfins was cranked all the way over and the other wasn't moving much at all as the spinning started.

It's easier to see both events if you watch the video, but here are two screen grabs.

Being at an angle end the end pf the braking burn is not that unusual in itself. See footage from previous RTLS day landings. But it might have been worse than usual.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/05/2018 05:38 pm
Well, it was bound to happen eventually.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OnWithTheShow on 12/05/2018 05:39 pm
This gives gives some evidence to the thread on whether stages target to undershoot, overshoot, or center the pad and then vector in after landing burn start up. It seems they may target an undershoot.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 05:39 pm
https://twitter.com/elonmusk/status/1070386062164283392

I can't wait to see video of that... amazing if the landing burn was able to get it under semi control from that spin.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: chrisking0997 on 12/05/2018 05:40 pm
https://twitter.com/elonmusk/status/1070386062164283392

...unreal
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Tomness on 12/05/2018 05:41 pm
https://twitter.com/elonmusk/status/1070386062164283392
Hopefully they are able to recover it, not need another Gun Ship from the Air Force
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kessdawg on 12/05/2018 05:41 pm
https://twitter.com/elonmusk/status/1070386554068119553
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RedLineTrain on 12/05/2018 05:41 pm
Amazing that it is still transmitting after going through that ordeal!
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Halidon on 12/05/2018 05:42 pm
https://twitter.com/elonmusk/status/1070386062164283392
Hopefully they are able to recover it, not need another Gun Ship from the Air Force
Heh, I think it's a wee bit too close to civilization for that sort of option.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: deruch on 12/05/2018 05:42 pm
This gives gives some evidence to the thread on whether stages target to undershoot, overshoot, or center the pad and then vector in after landing burn start up. It seems they may target an undershoot.
Or it successfully achieved a divert.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: weepingdragon on 12/05/2018 05:43 pm
Before the "exciting stuff" happened had view of some sky writing. Anybody on the ground see what it said? Thought that was going to be something "new" to talk about during "routine" landings.  :'(

As far as the the round "ring" that came off. You can definitely see crystallization sticking out. Whether there is a physical object inside the ice or just ice that formed around a circular spot then released? No idea.  Will play around with zoom in vlc once downloaded.

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: VoodooForce on 12/05/2018 05:43 pm
Damn these unflight-proven boosters  :o
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kessdawg on 12/05/2018 05:43 pm
Crazy!

https://twitter.com/elonmusk/status/1070387162892259329
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/05/2018 05:43 pm
So, did the first stage have enough control left to deliberately divert to the ocean, or was the original trajectory to the ocean with a planned divert to the landing pad only if all was ok?

It likely relied on the lift vector to carry it to shore before landing burn and once it went into an uncontrolled spin, it pretty much went down where the reentry burn targeted it.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: EnigmaSCADA on 12/05/2018 05:43 pm
Everyday Astronaut played a video of it a few minutes ago. Looked wild and then much calmer as landing burn started.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 05:43 pm
https://www.youtube.com/watch?v=-gYDHmcCztc

Amazing to almost recover...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Mongo62 on 12/05/2018 05:44 pm
Crazy!

https://twitter.com/elonmusk/status/1070387162892259329

Time enough to refurbish for the in-flight abort?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/05/2018 05:44 pm
No explosion in the video posted above on landing. That is impressive.
There was smoke just above the trees on the right immediately after.  Where there's smoke there's fire they say.  And if not an explosion at least there would be a bursting of the pressurized tanks.  What seems to be missing is the COPVs taking flight as we've seen before.

Betcha the folks at Vandenburg that prevented SSO-A from coming down near NROL-71 are feeling justified right now.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: DigitalMan on 12/05/2018 05:45 pm
This gives gives some evidence to the thread on whether stages target to undershoot, overshoot, or center the pad and then vector in after landing burn start up. It seems they may target an undershoot.
Or it successfully achieved a divert.

I was watching with my binoculars until it got very low where my view was blocked.  It did not look like there was any kind of divert.  I conclude it probably targeted an undershoot and would have had to do a maneuver somewhere to vector over to the landing pad.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: bdub217 on 12/05/2018 05:45 pm
At what point when you don't have complete control of your rocket flying back toward land does range safety kick in? While i'm sure they are happy they got their rocket back (albeit a little wet) I expect we will need to be asking some questions about whether the automated flight termination system worked as it was designed - and if it did - who didn't trigger a manual termination and why not? Dangerous as hell.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Roy_H on 12/05/2018 05:45 pm
So, did the first stage have enough control left to deliberately divert to the ocean, or was the original trajectory to the ocean with a planned divert to the landing pad only if all was ok?

Sorry for posting this in Updates, I thought I was in Discussion.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ZachS09 on 12/05/2018 05:46 pm
Crazy, that's the first failed landing since June of 2016.

Actually, the first landing failure since the Falcon Heavy center core’s landing failure, as that is technically based off of F9 technology.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ClayJar on 12/05/2018 05:47 pm
When the roll seemed to drastically accelerate right around the time they called transonic, the upper right grid fin in the frame appeared to be hard-over (due to hydraulic pump stall, apparently).  Would that suddenly greater rotation be a logical result of transonic choking of the flow in the grid fins, meaning the grid fin instead of working to slow the rotation would be acting more like a solid paddle and doing the opposite?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 05:47 pm
At what point when you don't have complete control of your rocket flying back toward land does range safety kick in? While i'm sure they are happy they got their rocket back (albeit a little wet) I expect we will need to be asking some questions about whether the automated flight termination system worked as it was designed - and if it did - who didn't trigger a manual termination and why not? Dangerous as hell.

This has been discussed previously, but let me re-iterate:

1. The end of the boost-back puts it on a trajectory that targets the ocean. (we just saw this)
2. The grid fins (if they work) move the impact/landing point to the pad or just past it.
3. The landing burn aims at the pad.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/05/2018 05:47 pm
Last words from the SpaceX launch host before the stage diverged: "It is SO exciting along the Space Coast!"

My last words before - "they've really got this landing thing down like clockwork, Sammy" (dog).

Sorry, it was me that caused it.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/05/2018 05:48 pm
So, did the first stage have enough control left to deliberately divert to the ocean, or was the original trajectory to the ocean with a planned divert to the landing pad only if all was ok?

All evidence, including visual, from previous missions suggest it flies a lifting entry from after  reentry burn till landing burn. Once 3-axis control was lost, the lift was lost as well.

Frankly, I'm surprised the AFTS didn't terminate and it still executed a soft landing off shore.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: chrisking0997 on 12/05/2018 05:48 pm
At what point when you don't have complete control of your rocket flying back toward land does range safety kick in? While i'm sure they are happy they got their rocket back (albeit a little wet) I expect we will need to be asking some questions about whether the automated flight termination system worked as it was designed - and if it did - who didn't trigger a manual termination and why not? Dangerous as hell.

IIRC, termination wouldnt be needed if this case.  Going in the water is the plan.   Its only dangerous if the booster is off the planned path
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: AC in NC on 12/05/2018 05:48 pm
Booster might still be reused!

https://twitter.com/elonmusk/status/1070387162892259329

Abort test candidate.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: tyrred on 12/05/2018 05:49 pm
What manual termination? They use automatic flight termination systems now, no? Don't they safe AFTS for landings? Pretty sure I've heard that call out on landings for a while now. Or maybe I just goes crazy.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: tonya on 12/05/2018 05:49 pm
Everyday Astronaut played a video of it a few minutes ago. Looked wild and then much calmer as landing burn started.
It looked like the leg deploy reduced the roll quite swiftly, much like an ice skater but aerodynamic drag may have slowed it more than the shifting weight.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Roy_H on 12/05/2018 05:49 pm
At what point when you don't have complete control of your rocket flying back toward land does range safety kick in? While i'm sure they are happy they got their rocket back (albeit a little wet) I expect we will need to be asking some questions about whether the automated flight termination system worked as it was designed - and if it did - who didn't trigger a manual termination and why not? Dangerous as hell.

Why would they blow the rocket up when the trajectory was in the ocean?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 05:50 pm
So, did the first stage have enough control left to deliberately divert to the ocean, or was the original trajectory to the ocean with a planned divert to the landing pad only if all was ok?

All evidence, including visual, from previous missions suggest it flies a lifting entry from after  reentry burn till landing burn. Once 3-axis control was lost, the lift was lost as well.

Frankly, I'm surprised the AFTS didn't terminate and it still executed a soft landing off shore.

They might have if it was heading for land... But they could certainly see its trajectory. Would you prefer to fish up one big thing from the ocean or thousands of pieces of debris?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/05/2018 05:50 pm
At what point when you don't have complete control of your rocket flying back toward land does range safety kick in?

If it didn't exceed the reentry corridor ground track, why would it?

I don't know if roll rate is a consideration for AFTS, though. Seems not.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: lrk on 12/05/2018 05:50 pm
At what point when you don't have complete control of your rocket flying back toward land does range safety kick in? While i'm sure they are happy they got their rocket back (albeit a little wet) I expect we will need to be asking some questions about whether the automated flight termination system worked as it was designed - and if it did - who didn't trigger a manual termination and why not? Dangerous as hell.

F9 uses AFTS, I don't think there is a manual option anymore.  But that is only triggered if the booster deviates more than a set amount from the planned trajectory, and apparently landing a few hundred feet away from the target isn't enough of a deviation.  Also I think the last-minute "dogleg" maneuver that put it in the water was automatically triggered when the booster sensed that it wasn't going to make the landing. 
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: yokem55 on 12/05/2018 05:51 pm
So, did the first stage have enough control left to deliberately divert to the ocean, or was the original trajectory to the ocean with a planned divert to the landing pad only if all was ok?

All evidence, including visual, from previous missions suggest it flies a lifting entry from after  reentry burn till landing burn. Once 3-axis control was lost, the lift was lost as well.

Frankly, I'm surprised the AFTS didn't terminate and it still executed a soft landing off shore.
An AFTS termination could have been more dangerous (in terms of debris risk) than just letting it attempt a soft splashdown. As long as the vehicle was remaining on a safe vector, letting it get lower and lower and do it's thing was improving the safety of the situation.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: dlapine on 12/05/2018 05:51 pm
Latest Elon tweet update-

"Pump is single string. Some landing systems are not redundant, as landing is considered ground safety critical, but not mission critical. Given this event, we will likely add a backup pump & lines."
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: EnigmaSCADA on 12/05/2018 05:52 pm
I think I'll pass on a that PTP vacation unless I'm diagnosed with something inoperable/terminal with less than 6 weeks to live.

Almost needed a Dramamine watching on YouTube.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jtrame on 12/05/2018 05:52 pm
At what point when you don't have complete control of your rocket flying back toward land does range safety kick in? While i'm sure they are happy they got their rocket back (albeit a little wet) I expect we will need to be asking some questions about whether the automated flight termination system worked as it was designed - and if it did - who didn't trigger a manual termination and why not? Dangerous as hell.

Why would they blow the rocket up when the trajectory was in the ocean?

This area offshore was cleared of traffic way before the flight, right?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: sghill on 12/05/2018 05:52 pm
Everyday Astronaut played a video of it a few minutes ago. Looked wild and then much calmer as landing burn started.
It looked like the leg deploy reduced the roll quite swiftly, much like an ice skater but aerodynamic drag may have slowed it more than the shifting weight.

As it slowed down, the stuck grid fins would have less authority (because there is not as much air flowing through them) and the RCS would have more authority. Makes sense that it looked more stable right as it neared a dead stop.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/05/2018 05:53 pm

Elon Musk twitter

‏Grid fin hydraulic pump stalled, so Falcon landed just out to sea. Appears to be undamaged & is transmitting data. Recovery ship dispatched.

I recall the last time they said they sent a recovery ship after a non-kaboom water landed F9.  They blew it up.  Was that by shooting it?  It'll be interesting, how do you approach such a thing unless there's a way to de-pressurize it?  Then once you have it under tugboat control what do you do with it??  It'll be close to shore, possibly drifting rear the port entry, possibly having a hazard zone that precludes cruise ships from coming in / out of port.

But how can it be intact if there was a smoke puff visible above the trees in the first video???  Oh... The smoke must have been reflected exhaust smoke and water from the surface.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Johnnyhinbos on 12/05/2018 05:54 pm
At what point when you don't have complete control of your rocket flying back toward land does range safety kick in? While i'm sure they are happy they got their rocket back (albeit a little wet) I expect we will need to be asking some questions about whether the automated flight termination system worked as it was designed - and if it did - who didn't trigger a manual termination and why not? Dangerous as hell.
Isn't AFTS for the booster safed around boostback? What would unzipping the stage do with the minimal fuel left at that point?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: matthewkantar on 12/05/2018 05:54 pm
I clocked the stage had about 36 RPM during the burn.

On edit, 9 rpm, forgot to divide by four after counting legs going by.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Aurora on 12/05/2018 05:54 pm
Just before the first stage began to spin, the video shows a ring of something releasing by the left fin.  The announcer said something about ice releasing - this was not ice.   Maybe a seal on one of the hydraulic controls of the fins?

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Tass on 12/05/2018 05:55 pm
No explosion in the video posted above on landing. That is impressive.
There was smoke just above the trees on the right immediately after.  Where there's smoke there's fire they say.  And if not an explosion at least there would be a bursting of the pressurized tanks.  What seems to be missing is the COPVs taking flight as we've seen before.

Betcha the folks at Vandenburg that prevented SSO-A from coming down near NROL-71 are feeling justified right now.

Nope. Intact and still transmitting per Elon.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: DigitalMan on 12/05/2018 05:55 pm
At what point when you don't have complete control of your rocket flying back toward land does range safety kick in? While i'm sure they are happy they got their rocket back (albeit a little wet) I expect we will need to be asking some questions about whether the automated flight termination system worked as it was designed - and if it did - who didn't trigger a manual termination and why not? Dangerous as hell.

Why would they blow the rocket up when the trajectory was in the ocean?

This area offshore was cleared of traffic way before the flight, right?

There are documents that show the zones that are  cleared for launch if you are curious exactly what areas are keep out.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kevinof on 12/05/2018 05:56 pm
It was ice and it came off the booster at the lower end, not where the fins are.

Just before the first stage began to spin, the video shows a ring of something releasing by the left fin.  The announcer said something about ice releasing - this was not ice.   Maybe a seal on one of the hydraulic controls of the fins?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: punder on 12/05/2018 05:56 pm
Hard to tell with the long lens but the landing looked verrrry close to the shore. Hopefully an easy recovery.

Well, easy-ish.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/05/2018 05:57 pm
Isn't AFTS for the booster safed around boostback?
Not around boostback, but it might be around the transonic regime, actually.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: envy887 on 12/05/2018 05:57 pm
I think I'll pass on a that PTP vacation unless I'm diagnosed with something inoperable/terminal with less than 6 weeks to live.

Almost needed a Dramamine watching on YouTube.

BFS won't have grid fins or non-redundant hydraulic loops.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RoboGoofers on 12/05/2018 05:57 pm
it sure did seem like it was using a lot of RCS pretty late, when you'd expect the fins to be actuating.

it makes me wonder if the stuck fin was doing more harm than good and if they should passively fail to a flush to body position.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 05:58 pm
https://twitter.com/johnkrausphotos/status/1070385056877895682

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 05:59 pm
A short clip before the video was cut from the stage. As Elon says, definitely a grid find issue. They did not move here:
https://twitter.com/nextspaceflight/status/1070383431123722240
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/05/2018 06:03 pm
There's already amateur footage of the landing attempt online.  It looks like one of the grid fins went hardover and got stuck.  Amazingly, the rocket managed to neutralize the roll and perform a soft touchdown anyway, but as it was on water it fell over and ruptured after touching down.

From the video I saw, it was still rolling during the landing / splashdown
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: EnigmaSCADA on 12/05/2018 06:05 pm
I think I'll pass on a that PTP vacation unless I'm diagnosed with something inoperable/terminal with less than 6 weeks to live.

Almost needed a Dramamine watching on YouTube.

BFS won't have grid fins or non-redundant hydraulic loops.
I wasn't being serious. Obviously.

However, to your point, I'm not sure what you said really matters that much at this point, while of course there will be more robust/redundant systems (eventually), this landing attempt undeniably illustrates how much further we need things to be for propulsive landing of people (especially for the purposes of leisure travel) to become something. We can't claim BFR will be more reliable considering it hasn't even done a hop test.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: toruonu on 12/05/2018 06:08 pm
However, to your point, I'm not sure what you said really matters that much at this point, while of course there will be more robust/redundant systems, this landing attempt undeniably illustrates how much further we need things to be for propulsive landing of people (especially for the purposes of leisure travel) to become something. We can't claim BFR will be more reliable considering it hasn't even done a hop test.

Propulsive landing wasn't the issue here. Actually propulsive landing probably saved the stage and it made a soft landing. Had the stage been recovered using parachutes such spin I'd assume would tangle them and kill the chute system. So the propulsive landing IS the right choice if one were just looking at this footage :) Loss of a major control surface that actually worked against the system is what caused the issue here and gives though on how this will impact the BFS landings if one of the control surfaces seriously locks up.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: oldAtlas_Eguy on 12/05/2018 06:09 pm
There's already amateur footage of the landing attempt online.  It looks like one of the grid fins went hardover and got stuck.  Amazingly, the rocket managed to neutralize the roll and perform a soft touchdown anyway, but as it was on water it fell over and ruptured after touching down.

From the video I saw, it was still rolling during the landing / splashdown
From SpaceX the booster was still transmitting telemetry meaning it was floating and not ruptured.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: matthewkantar on 12/05/2018 06:10 pm
There's already amateur footage of the landing attempt online.  It looks like one of the grid fins went hardover and got stuck.  Amazingly, the rocket managed to neutralize the roll and perform a soft touchdown anyway, but as it was on water it fell over and ruptured after touching down.

From the video I saw, it was still rolling during the landing / splashdown

The last bit of video, as the legs deploy, focusing on the white spot where the leg was the rotation seemed to have stopped completely. Surprising as the roll rate was wild.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 06:11 pm
A view from the air... It landed much farther out in the ocean than it seemed from the one telephoto video:

https://twitter.com/flying_briann/status/1070392207696453632
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kevinof on 12/05/2018 06:11 pm
That really is damn good control - You basically had two controls working against each other all the way down and yet it did a controlled landing and no big kaboom.

Impressive stuff.

There's already amateur footage of the landing attempt online.  It looks like one of the grid fins went hardover and got stuck.  Amazingly, the rocket managed to neutralize the roll and perform a soft touchdown anyway, but as it was on water it fell over and ruptured after touching down.

From the video I saw, it was still rolling during the landing / splashdown
From SpaceX the booster was still transmitting telemetry meaning it was floating and not ruptured.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: deruch on 12/05/2018 06:12 pm
It was ice and it came off the booster at the lower end, not where the fins are.

No, go to the launch video and watch starting around T+5:50. The perspective is messing with you but you can clearly see that it is a small ring up close, not a bigger ring farther away from the camera. There's frames where you can see it in front of the gridfin, i.e. between the camera and the gridfin.

It may have been ice, no comment on that.  Just that it was from the area around the gridfins and actually bumped into the one on the left before it started floating up and away.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: testguy on 12/05/2018 06:13 pm
Still a pretty remarkable record of successful recoveries after the first landing. I suspect few in this forum would have predicted the success rate at this point. The fix to this particular problem seams pretty simple. I for one would give SpaceX an attaboy for what has been achieved to date.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kraisee on 12/05/2018 06:16 pm
Watched from Cocoa Beach.   With Mk 1 eyeballs and with binoculars, it was clearly a wild ride down!

Assuming the stage landed just offshore of LZ1, ground winds are currently ~16 mph out of the NNW, so it is not going to take long before it is blown onto the beach somewhere along the peninsula.

https://www.google.com/maps/place/28%C2%B029'09.3%22N+80%C2%B032'40.1%22W/@28.4859214,-80.5795065,11129m/data=!3m1!1e3!4m6!3m5!1s0x0:0x0!7e2!8m2!3d28.4859216!4d-80.5444718

I'd imagine that a stage lying on its side with legs extended, encountering the shallow seabed, would not be good for the structure.

I hope they can get to it quickly.

Ross.

P.S. Re: The last one that landed in the ocean; we saw a squadron of 6x A-10 Warthogs arrive at Patrick AFB a day or so after the landing.   Never seen them before or since.   I believe they used that stage as live target practice because it still contained propellants and couldn't be towed safely back into Port Canaveral.   Not sure what they can do with this stage, so close to shore.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/05/2018 06:17 pm
That really is damn good control - You basically had two controls working against each other all the way down and yet it did a controlled landing and no big kaboom.

Impressive stuff.

There's already amateur footage of the landing attempt online.  It looks like one of the grid fins went hardover and got stuck.  Amazingly, the rocket managed to neutralize the roll and perform a soft touchdown anyway, but as it was on water it fell over and ruptured after touching down.

From the video I saw, it was still rolling during the landing / splashdown
From SpaceX the booster was still transmitting telemetry meaning it was floating and not ruptured.

Yeah from the point of view of someone doing control systems, seeing this booster spin, battling aerodynamic forces and its own unresponsive actuators all the way down, and then making a recovery from such an extreme flight state and attitude and landing intact, that's like - control system porn!

I'm sure some people involved in the control system design at SpaceX will watch this over and over and over - with full telemetry visualisation. They're probably also going to show it to all new employees and interns, for years to come. This is glorious.

If they can safely recover the booster and offload the onboard data and get the hardware analyzed... thats not a failure then, its way better than a success. no success ever gives you that much awesome data to learn from! (Unless, you are doing a scientific lander mission to mars or something like that)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: oldAtlas_Eguy on 12/05/2018 06:19 pm
Still a pretty remarkable record of successful recoveries after the first landing. I suspect few in this forum would have predicted the success rate at this point. The fix to this particular problem seams pretty simple. I for one would give SpaceX an attaboy for what has been achieved to date.
The most important point is that they will have the actual hardware to inspect to see what failed. Whether this booster ever flies again or not is secondary.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: oiorionsbelt on 12/05/2018 06:19 pm
Any clues a to what boat would have been dispatched to aid the booster?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/05/2018 06:20 pm
As it slowed down, the stuck grid fins would have less authority (because there is not as much air flowing through them) and the RCS would have more authority. Makes sense that it looked more stable right as it neared a dead stop.
True that.  You could definitely see the roll rate reducing in the last 10 seconds or so.

Also, I think some of the early gyrations (as opposed to simple roll) early on could have been attributed to (once some rotation was started) the bad fin and the fins that were attempting correction rotating into and out of the airstream.  Keep in mind that at that point the stage is presented at some angle to the oncoming airstream so that the body lift can do the bulk of the horizontal movement.

Can someone in the know please comment on whether the control system and engine gimbaling would be likely to be effective at the high roll rates we saw or at the lower roll rate we saw later?  You can clearly see in the video that the engine is firing off to the side and that the direction is changing relative to the fixed ground based camera but I wonder if this was GNC and engine successfully working to do their job despite the roll or if the engine is at a fixed angle to the centerline of the stage and the redirection is only due to the roll.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: tonya on 12/05/2018 06:21 pm
Everyday Astronaut played a video of it a few minutes ago. Looked wild and then much calmer as landing burn started.
It looked like the leg deploy reduced the roll quite swiftly, much like an ice skater but aerodynamic drag may have slowed it more than the shifting weight.

As it slowed down, the stuck grid fins would have less authority (because there is not as much air flowing through them) and the RCS would have more authority. Makes sense that it looked more stable right as it neared a dead stop.

That makes sense, and the legs are inline with the fins. As soon as the legs start to deploy, what little airflow there is over the fins will be turbulent. I couldn't see it in the video, but likely to be RCS that killed the roll.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mme on 12/05/2018 06:22 pm
A view from the air... It landed much farther out in the ocean than it seemed from the one telephoto video:

https://twitter.com/flying_briann/status/1070392207696453632
I think that this supports (admittedly as a single data point) that it probably targets the IIP offshore for a significant portion of the landing.

My biggest concern is all the concern trolly articles that will be released now. Especially for commercial crew.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vanoord on 12/05/2018 06:23 pm
At what point when you don't have complete control of your rocket flying back toward land does range safety kick in? While i'm sure they are happy they got their rocket back (albeit a little wet) I expect we will need to be asking some questions about whether the automated flight termination system worked as it was designed - and if it did - who didn't trigger a manual termination and why not? Dangerous as hell.

I wonder if - as long as they've got the visual feedback in realtime - that it makes as much sense to let it drop into the ocean rather than blow it.

For a start, there's much less propellant to pollute the ocean...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RDMM2081 on 12/05/2018 06:24 pm
Observation: During the initial grid fin deployment, they deployed to their "flight configuration position" very slowly.  I assume this is because of the hydraulic pump issue, however the announcer clearly said something to the effect:  "The grid fins are deploying nice and slow so (some reason)".

Which is true or more likely given that we now know there was a serious issue with the grid fin hydraulic pump system?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/05/2018 06:24 pm
I wonder if - as long as they've got the visual feedback in realtime - that it makes as much sense to let it drop into the ocean rather than blow it.

Visual feedback has nothing to do with it any longer, F9 flies an automated flight termination system with no ground input.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: oldAtlas_Eguy on 12/05/2018 06:25 pm
Everyday Astronaut played a video of it a few minutes ago. Looked wild and then much calmer as landing burn started.
It looked like the leg deploy reduced the roll quite swiftly, much like an ice skater but aerodynamic drag may have slowed it more than the shifting weight.

As it slowed down, the stuck grid fins would have less authority (because there is not as much air flowing through them) and the RCS would have more authority. Makes sense that it looked more stable right as it neared a dead stop.

That makes sense, and the legs are inline with the fins. As soon as the legs start to deploy, what little airflow there is over the fins will be turbulent. I couldn't see it in the video, but likely to be RCS that killed the roll.
Transfer of momentum. When the legs deploy they transfer momentum slowing the roll. When that occurred the control system had enough authority to finish the roll dampening just before surface contact. It might have even survived a land landing.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: envy887 on 12/05/2018 06:26 pm
Observation: During the initial grid fin deployment, they deployed to their "flight configuration position" very slowly.  I assume this is because of the hydraulic pump issue, however the announcer clearly said something to the effect:  "The grid fins are deploying nice and slow so (some reason)".

Which is true or more likely given that we now know there was a serious issue with the grid fin hydraulic pump system?

The TI fins have always deployed much more slowly than the aluminum ones. That didn't look unusual to me.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Scylla on 12/05/2018 06:27 pm
Observation: During the initial grid fin deployment, they deployed to their "flight configuration position" very slowly.  I assume this is because of the hydraulic pump issue, however the announcer clearly said something to the effect:  "The grid fins are deploying nice and slow so (some reason)".

Which is true or more likely given that we now know there was a serious issue with the grid fin hydraulic pump system?
Titanium fins have always deployed much slower than aluminum fins.

Argg....Ninjad...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: dnavas on 12/05/2018 06:28 pm
https://twitter.com/elonmusk/status/1070388894875545600

Quote
Pump is single string. Some landing systems are not redundant, as landing is considered ground safety critical, but not mission critical. Given this event, we will likely add a backup pump & lines.

Uhm, pre-DM-1?  How likely are they to get an exception for this...?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kevinof on 12/05/2018 06:30 pm
It has nothing to do with the launch. It's for landing only.

https://twitter.com/elonmusk/status/1070388894875545600

Quote
Pump is single string. Some landing systems are not redundant, as landing is considered ground safety critical, but not mission critical. Given this event, we will likely add a backup pump & lines.

Uhm, pre-DM-1?  How likely are they to get an exception for this...?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 06:30 pm
https://twitter.com/elonmusk/status/1070388894875545600

Quote
Pump is single string. Some landing systems are not redundant, as landing is considered ground safety critical, but not mission critical. Given this event, we will likely add a backup pump & lines.

Uhm, pre-DM-1?  How likely are they to get an exception for this...?

Why do they need one? The landings are not part of the main mission.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: envy887 on 12/05/2018 06:30 pm
https://twitter.com/elonmusk/status/1070388894875545600

Quote
Pump is single string. Some landing systems are not redundant, as landing is considered ground safety critical, but not mission critical. Given this event, we will likely add a backup pump & lines.

Uhm, pre-DM-1?  How likely are they to get an exception for this...?

They don't need to change anything for DM-1.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kevinof on 12/05/2018 06:31 pm
https://twitter.com/elonmusk/status/1070399755526656000
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: oldAtlas_Eguy on 12/05/2018 06:33 pm
https://twitter.com/elonmusk/status/1070388894875545600

Quote
Pump is single string. Some landing systems are not redundant, as landing is considered ground safety critical, but not mission critical. Given this event, we will likely add a backup pump & lines.

Uhm, pre-DM-1?  How likely are they to get an exception for this...?
This is a recovery issue only. DM-1 can proceed even if no changes are made.

The only impact from NASA HSF Safety is that multiple flights with the new hardware fly demonstrating no interaction of the changes with any launch systems before DM-2.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: StuffOfInterest on 12/05/2018 06:33 pm
I wonder if the control software could be modified so that when a fin freezes the fin on the opposite side can be placed in a position to dampen the action of the first one and then let the two other grids fins do all the work?  There wouldn't be as much control but if it can avoid a roll then there may be enough to get the booster down.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: VoodooForce on 12/05/2018 06:33 pm
wow amazing footage
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 06:34 pm
Based on the full landing video that Elon posted, looks like the leg deployment momentum shift had the most impact in reducing the roll. (like a spinning figure skater)

And it looks like the grid fins were locked in a position to increase the roll... So the RCS fought that roll all the way down.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: yokem55 on 12/05/2018 06:34 pm
https://twitter.com/elonmusk/status/1070388894875545600

Quote
Pump is single string. Some landing systems are not redundant, as landing is considered ground safety critical, but not mission critical. Given this event, we will likely add a backup pump & lines.

Uhm, pre-DM-1?  How likely are they to get an exception for this...?
Because it's a recovery only system that has no impact on the safe flight of the primary mission. And as demonstrated today, thus particular system was able to fail in a way that preserved the safety of life and property.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: quagmire on 12/05/2018 06:35 pm
https://twitter.com/elonmusk/status/1070388894875545600

Quote
Pump is single string. Some landing systems are not redundant, as landing is considered ground safety critical, but not mission critical. Given this event, we will likely add a backup pump & lines.

Uhm, pre-DM-1?  How likely are they to get an exception for this...?

In all reality, this shouldn't affect DM-1 as it involves the landing systems and as Musk stated, it wasn't Mission critical.

In conspiracy theory world, yeah the anti-new space faction may want to go, " What else is not considered mission critical and need another complete review of the Falcon 9's systems!" in order to get Starliner to be the first. ;)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: toruonu on 12/05/2018 06:35 pm
I wonder if the control software could be modified so that when a fin freezes the fin on the opposite side can be placed in a position to dampen the action of the first one and then let the two other grids fins do all the work?  There wouldn't be as much control but if it can avoid a roll then there may be enough to get the booster down.

If you look at the video Elon shared it looked like none of the fins worked. So likely that a fin was working for a moment as this span out, but they locked in place pretty soon after...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/05/2018 06:36 pm
I wonder if the control software could be modified so that when a fin freezes the fin on the opposite side can be placed in a position to dampen the action of the first one and then let the two other grids fins do all the work?  There wouldn't be as much control but if it can avoid a roll then there may be enough to get the booster down.

How do you propose to do that if all the fins are powered by the single pump?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/05/2018 06:37 pm
At what point when you don't have complete control of your rocket flying back toward land does range safety kick in? While i'm sure they are happy they got their rocket back (albeit a little wet) I expect we will need to be asking some questions about whether the automated flight termination system worked as it was designed - and if it did - who didn't trigger a manual termination and why not? Dangerous as hell.

From what we heard in press conferences, the AFTS is completely autonomous, there is no "red button" at the range anymore, instead the rocket itself destructs itself if it leaves a predefined safety corridor (or is about to leave and has insufficient control authority to go back to it)
while F9 was obviously having troubles with control authority, the stage was apparently fully aware of its state and had at least "some" control (otherwise the water landing would have failed) as such its likely it never left or even trended outside of the save-flight corridor and as such the AFTS had no reason to ever command a destruction. It did behave exactly as designed for an off-nominal landing, which is land at the safety-backup point just off shore.

I'm sure no-one at SpaceX expected to see that code branch executing outside of a simulator test anytime soon, but it did, and apparently, flawlessly ;)

In the history of space flight, automatic termination has been commanded based on much simpler triggers, such as exceeding certain angle of attacks, attitudes or rotation rates, but that was at an age when state estimation wasn't as good and you had to assume that such a flight situation was unrecoverable anyway due to inertial systems failing and being unable to compute the state.
Falcon 9 goes through some pretty extreme maneuvers during ordinary missions - for example during flip- and boostback but also during reentry and supersonic High-AoA flight. Its unlikely it would have exceeded the design limits of its control system per se, the only issue was the stuck fin(s)

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ellindsey on 12/05/2018 06:38 pm
How does a single engine counter roll?  This was a single-engine landing, not a three-engine landing, unless I'm mistaken.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: DanielW on 12/05/2018 06:39 pm
I wonder if the control software could be modified so that when a fin freezes the fin on the opposite side can be placed in a position to dampen the action of the first one and then let the two other grids fins do all the work?  There wouldn't be as much control but if it can avoid a roll then there may be enough to get the booster down.

If you countered the roll it would change the angle of attack to something undesirable.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: edzieba on 12/05/2018 06:39 pm
  It'll be interesting, how do you approach such a thing unless there's a way to de-pressurize it?  Then once you have it under tugboat control what do you do with it?? 
Same way the Europeans recovery potentially explosive boosters after splashdown: with Frenchmen (http://papyone.over-blog.com/2015/09/ariane-503-or-the-story-of-my-last-offshore-project.html).
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mlindner on 12/05/2018 06:40 pm
WOW!

https://twitter.com/elonmusk/status/1070399755526656000

It's amazing watching the entire structure flex and bend from the torques being put on the grid finds and then the whole structure twist when it impacts the water but holds together! That's some incredible engineering!
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 06:41 pm
How does a single engine counter roll?  This was a single-engine landing, not a three-engine landing, unless I'm mistaken.

I think he by "engines" meant the RCS thrusters working together with the main engine to try to wrestle back control.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Johnnyhinbos on 12/05/2018 06:41 pm
I wonder if the control software could be modified so that when a fin freezes the fin on the opposite side can be placed in a position to dampen the action of the first one and then let the two other grids fins do all the work?  There wouldn't be as much control but if it can avoid a roll then there may be enough to get the booster down.
One pump - no fin actuation period. So software can't help...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mlindner on 12/05/2018 06:41 pm
How does a single engine counter roll?  This was a single-engine landing, not a three-engine landing, unless I'm mistaken.

Air drag will slow it down to some extent and also the moment the legs pop out the moment of inertia suddenly increases (like a skater sticking their arms out in a spin) causing an instant de-spin effect.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 06:42 pm
It's amazing watching the entire structure flex and bend from the torques being put on the grid finds and then the whole structure twist when it impacts the water but holds together! That's some incredible engineering!

I think most of the bending is actually the camera not being firmly enough attached to the stage. (due to G-forces)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ZachS09 on 12/05/2018 06:42 pm
How does a single engine counter roll?  This was a single-engine landing, not a three-engine landing, unless I'm mistaken.

Single-engine landing burns allow for more control authority; therefore, it stabilized the booster before splashing down. Three-engine landing burns are not meant to keep the booster stable. They’re meant for hoverslam scenarios when there is a really low fuel margin and they have to slam on the brakes at the last second and shut down as soon as the legs reach the ground or drone ship.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/05/2018 06:43 pm
Latest Elon tweet update-

"Pump is single string. Some landing systems are not redundant, as landing is considered ground safety critical, but not mission critical. Given this event, we will likely add a backup pump & lines."

Block 5.1
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: oldAtlas_Eguy on 12/05/2018 06:44 pm
At the moment it looks like a low hydraulic pressure event sticking a grid fin in a bad position and cause the others to be insufficient control authority to counteract the bad fin. The current suspect is the pump. But it may be something else. Will have to wait for the full hardware and telemetry reviews for certainty of what failed and how.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/05/2018 06:44 pm
How does a single engine counter roll?  This was a single-engine landing, not a three-engine landing, unless I'm mistaken.

Single-engine landing burns allow for more control authority

A single M1d engine provides no roll control authority.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: edzieba on 12/05/2018 06:45 pm
Does Falcon still have independent gas-generator nozzle actuation for the centre Merlin, or was that dumped in the move to the octaweb?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ZachS09 on 12/05/2018 06:45 pm
How does a single engine counter roll?  This was a single-engine landing, not a three-engine landing, unless I'm mistaken.

Single-engine landing burns allow for more control authority

A single M1d engine provides no roll control authority.

My mistake. Maybe I read the single-engine landing burn purpose the wrong way.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/05/2018 06:45 pm
I wonder if the control software could be modified so that when a fin freezes the fin on the opposite side can be placed in a position to dampen the action of the first one and then let the two other grids fins do all the work?  There wouldn't be as much control but if it can avoid a roll then there may be enough to get the booster down.

That won't work. A hardover fin will not just cause a spin but also a pitching moment. If the opposite side fin tries to counter the spin, it will worsen the pitch. if it tries to counter the pitch, it will worsen the spin. Since pitching over while spinning makes things worse, (causing a tailspin like motion which probably stalls the gridfins and causes complete loss of control or breakup) it would have to counter the pitching moment, which worsens the spin, and then have the other two perpendicular fins try to counter that and spin the other direction.

Issue with that is, then you have 4 fins in hardover and no control authority whatsoever. Its better to "life" with a bit of spin and have some control authority at least in the second set of perpendicular fins, so you can control the trajectory

remarkably, that seems to be what the stage did, as it never really went off course (if it had, AFTS would have needed to intervene) aside from the preprogrammed contingency-landing location just off the coast, which SpaceX mentioned in the past.



Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: chawleysnow on 12/05/2018 06:45 pm
Did they just get lucky that the turbopump torque was opposite the grid fin torque?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 06:46 pm
Latest Elon tweet update-

"Pump is single string. Some landing systems are not redundant, as landing is considered ground safety critical, but not mission critical. Given this event, we will likely add a backup pump & lines."

Block 5.1

I see Jim is here to expose the great lie that there would never be any tweaks to block 5!  ;D
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ellindsey on 12/05/2018 06:46 pm
Does Falcon still have independent gas-generator nozzle actuation for the centre Merlin, or was that dumped in the move to the octaweb?
As far as I am aware, the actuated gas generator exhaust nozzle for roll control was only present on the vacuum Merlin engines, and was removed on the D version of those.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/05/2018 06:46 pm
Does Falcon still have independent gas-generator nozzle actuation for the centre Merlin, or was that dumped in the move to the octaweb?

Dumped, on the first stage it was only ever available on the Falcon 1.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mlindner on 12/05/2018 06:47 pm
How does a single engine counter roll?  This was a single-engine landing, not a three-engine landing, unless I'm mistaken.

Air drag will slow it down to some extent and also the moment the legs pop out the moment of inertia suddenly increases (like a skater sticking their arms out in a spin) causing an instant de-spin effect.

Additionally, a spinning object will want to spin along it's maximum moment of inertia. The rocket spinning on its long axis will slowly gain rotation turning it into a "flat spin" however a flat spin has lots of air drag and can also be counteracted by the rocket propulsion. As the rocket constantly takes energy out of the flat spin the overall spin rate will reduce.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: oldAtlas_Eguy on 12/05/2018 06:47 pm
Latest Elon tweet update-

"Pump is single string. Some landing systems are not redundant, as landing is considered ground safety critical, but not mission critical. Given this event, we will likely add a backup pump & lines."

Block 5.1
Jim, I think the problem was that the weight issue on pre-BLK5 is the suspect. With BLK5 there is extra performance available such that the weight saving issues for the recovery only hardware can be rexamined. They already did that for the landing legs because there was an issue and BLK5 allowed for use of heavier legs.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/05/2018 06:47 pm
Everyday Astronaut played a video of it a few minutes ago. Looked wild and then much calmer as landing burn started.
It looked like the leg deploy reduced the roll quite swiftly, much like an ice skater but aerodynamic drag may have slowed it more than the shifting weight.

As it slowed down, the stuck grid fins would have less authority (because there is not as much air flowing through them) and the RCS would have more authority. Makes sense that it looked more stable right as it neared a dead stop.

That makes sense, and the legs are inline with the fins. As soon as the legs start to deploy, what little airflow there is over the fins will be turbulent. I couldn't see it in the video, but likely to be RCS that killed the roll.
Transfer of momentum. When the legs deploy they transfer momentum slowing the roll. When that occurred the control system had enough authority to finish the roll dampening just before surface contact. It might have even survived a land landing.

It was the leg deployment that did most of the work.  And the same change in rotational inertial would have made it harder for the control system.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: AncientU on 12/05/2018 06:47 pm
I wonder if the control software could be modified so that when a fin freezes the fin on the opposite side can be placed in a position to dampen the action of the first one and then let the two other grids fins do all the work?  There wouldn't be as much control but if it can avoid a roll then there may be enough to get the booster down.

That won't work. A hardover fin will not just cause a spin but also a pitching moment. If the opposite side fin tries to counter the spin, it will worsen the pitch. if it tries to counter the pitch, it will worsen the spin. Since pitching over while spinning makes things worse, (causing a tailspin like motion which probably stalls the gridfins and causes complete loss of control or breakup) it would have to counter the pitching moment, which worsens the spin, and then have the other two perpendicular fins try to counter that and spin the other direction.

Issue with that is, then you have 4 fins in hardover and no control authority whatsoever. Its better to "life" with a bit of spin and have some control authority at least in the second set of perpendicular fins, so you can control the trajectory

remarkably, that seems to be what the stage did, as it never really went off course (if it had, AFTS would have needed to intervene) aside from the preprogrammed contingency-landing location just off the coast, which SpaceX mentioned in the past.

Spin stabilized?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: dnavas on 12/05/2018 06:49 pm
The only impact from NASA HSF Safety is that multiple flights with the new hardware fly demonstrating no interaction of the changes with any launch systems before DM-2.

Right, that's my concern.  Do you delay DM-1 in order to not have to do that, or do you run with this change later, or do you forego making the change at all, or do you build two separate F9s, or....?

I'm also wondering since this is a landing-only system, to what extent the testing hurdle will be lower.

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Johnnyhinbos on 12/05/2018 06:49 pm
Meanwhile, over at Blue Origin...


"Vin, you got that? Double up the pump, and add in redundant lines while you're at it"


Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mlindner on 12/05/2018 06:50 pm
It's amazing watching the entire structure flex and bend from the torques being put on the grid finds and then the whole structure twist when it impacts the water but holds together! That's some incredible engineering!

I think most of the bending is actually the camera not being firmly enough attached to the stage. (due to G-forces)

No, the camera doesn't move with respect to the rocket body, only the fins twist.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: DanielW on 12/05/2018 06:51 pm
I would wonder if the engineers might talk Musk out of adding a redundant pump if they can just make the one more robust. I seems like understanding and fixing the issue is better than redundancy for a non-mission critical system.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RDMM2081 on 12/05/2018 06:52 pm
Observation: During the initial grid fin deployment, they deployed to their "flight configuration position" very slowly.  I assume this is because of the hydraulic pump issue, however the announcer clearly said something to the effect:  "The grid fins are deploying nice and slow so (some reason)".

Which is true or more likely given that we now know there was a serious issue with the grid fin hydraulic pump system?

The TI fins have always deployed much more slowly than the aluminum ones. That didn't look unusual to me.

Not sure how I never caught onto that fact but thank you for pointing it out.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 06:54 pm
It's amazing watching the entire structure flex and bend from the torques being put on the grid finds and then the whole structure twist when it impacts the water but holds together! That's some incredible engineering!

I think most of the bending is actually the camera not being firmly enough attached to the stage. (due to G-forces)

No, the camera doesn't move with respect to the rocket body, only the fins twist.

Look again. Or point out where you see bending. The camera is certainly shaken loose in the water impact.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/05/2018 06:54 pm
I would wonder if the engineers might talk Musk out of adding a redundant pump if they can just make the one more robust. I seems like understanding and fixing the issue is better than redundancy for a non-mission critical system.

Anyone count up how many flights it took for a pump to fail, counting all the other failed landings like running out of hydraulic fluid, running out of prop, etc.?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/05/2018 06:55 pm
...

Spin stabilized?

Heh. Back to the roots. Has been the tool of choice since the first rockets ever.

Its what I always do in Kerbal Space Program when I have asymmetric thrust failures and the rocket wants to pitch over during launch. Full roll, spin it up, and hope that the forces cancel out ;)

What's remarkable is that the rocket was able to ignite and perform its landing burn while spinning. Didn't SpaceX first water landing attempt fail because a spin centrifuged the propellant to the tank side walls and the pump inlets were running dry?

Obviously that got fixed ;)




Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: StuffOfInterest on 12/05/2018 06:57 pm
I wonder if the control software could be modified so that when a fin freezes the fin on the opposite side can be placed in a position to dampen the action of the first one and then let the two other grids fins do all the work?  There wouldn't be as much control but if it can avoid a roll then there may be enough to get the booster down.

How do you propose to do that if all the fins are powered by the single pump?

Ouch.  I thought originally it was independent pumps but I guess it is one pump driving all four actuators.  Definitely nothing that can be done there without a redundant string.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Doesitfloat on 12/05/2018 06:58 pm
Well no one has shown this yet.
During stage separation the 2nd Stage M-Vac engine ignited and blew bunch of fire'n stuff into stage 1.
Here are a couple screen grabs from the SpaceX feed. 
If there is only one pump for all the gridfins a break in any hydrolic line will eventualy  drain the entire system.
So system was probably fine till it got blasted by stage 2. 
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Oersted on 12/05/2018 06:58 pm
However, to your point, I'm not sure what you said really matters that much at this point, while of course there will be more robust/redundant systems, this landing attempt undeniably illustrates how much further we need things to be for propulsive landing of people (especially for the purposes of leisure travel) to become something. We can't claim BFR will be more reliable considering it hasn't even done a hop test.

Propulsive landing wasn't the issue here. Actually propulsive landing probably saved the stage and it made a soft landing. Had the stage been recovered using parachutes such spin I'd assume would tangle them and kill the chute system. So the propulsive landing IS the right choice if one were just looking at this footage :) Loss of a major control surface that actually worked against the system is what caused the issue here and gives though on how this will impact the BFS landings if one of the control surfaces seriously locks up.

Perhaps they will have a jettison system with explosive bolts / pyrotechnics for grid fins or control surfaces that get stuck in an unhelpful position. With partially redundant control surfaces that could "take over" for each other that would be helpful.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/05/2018 06:59 pm
Block 5.1

By the time they got to their ten reflights of a single booster goal, I fully expected it to get to something like 5.3 regardless of this...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kevinof on 12/05/2018 07:00 pm
There she blows..

https://twitter.com/ChrisG_NSF/status/1070407175611277314
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/05/2018 07:02 pm
Well no one has shown this yet.
During stage separation the 2nd Stage M-Vac engine ignited and blew bunch of fire'n stuff into stage 1.
Here are a couple screen grabs from the SpaceX feed. 
If there is only one pump for all the gridfins a break in any hydrolic line will eventualy  drain the entire system.
So system was probably fine till it got blasted by stage 2. 

That happens on literally every flight. You'd think that if the effect was so severe, they'd figure out by now that hardware was getting seriously damaged by those "fireworks".
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mme on 12/05/2018 07:04 pm
Well no one has shown this yet.
During stage separation the 2nd Stage M-Vac engine ignited and blew bunch of fire'n stuff into stage 1.
Here are a couple screen grabs from the SpaceX feed. 
If there is only one pump for all the gridfins a break in any hydrolic line will eventualy  drain the entire system.
So system was probably fine till it got blasted by stage 2.
This is pretty normal for RTLS quick flips. Maybe it's related, but I would not assume. I also think Musk is assuming in a way. Unless telemetry told them something specific, all they know is the grid fins locked up. I think they'll figure it out but I would wait for a real analysis of the first stage that will hence forth be named "Bob."
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Oersted on 12/05/2018 07:04 pm
Everyday Astronaut played a video of it a few minutes ago. Looked wild and then much calmer as landing burn started.
It looked like the leg deploy reduced the roll quite swiftly, much like an ice skater but aerodynamic drag may have slowed it more than the shifting weight.

As it slowed down, the stuck grid fins would have less authority (because there is not as much air flowing through them) and the RCS would have more authority. Makes sense that it looked more stable right as it neared a dead stop.

That makes sense, and the legs are inline with the fins. As soon as the legs start to deploy, what little airflow there is over the fins will be turbulent. I couldn't see it in the video, but likely to be RCS that killed the roll.
Transfer of momentum. When the legs deploy they transfer momentum slowing the roll. When that occurred the control system had enough authority to finish the roll dampening just before surface contact. It might have even survived a land landing.

If a stuck grid fin caused the roll I would say that the slowdown in speed had more to do with stopping the roll than any transfer of momentum from the leg deployment. At slow speed the reaction control thrusters could counteract the aerodynamic forces.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vanoord on 12/05/2018 07:04 pm
Well no one has shown this yet.
During stage separation the 2nd Stage M-Vac engine ignited and blew bunch of fire'n stuff into stage 1.
Here are a couple screen grabs from the SpaceX feed. 
If there is only one pump for all the gridfins a break in any hydrolic line will eventualy  drain the entire system.
So system was probably fine till it got blasted by stage 2.

It does that most of the time. Check Monday's footage and the same thing happened.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: DigitalMan on 12/05/2018 07:05 pm
Block 5.1

By the time they got to their ten reflights of a single booster goal, I fully expected it to get to something like 5.3 regardless of this...

I seem to recall a tweet about S2 reliability improvements during the tweet-fest about mini-BFS for F9 when it was determined SpaceX would not be doing mini-BFS.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 07:06 pm
Everyday Astronaut played a video of it a few minutes ago. Looked wild and then much calmer as landing burn started.
It looked like the leg deploy reduced the roll quite swiftly, much like an ice skater but aerodynamic drag may have slowed it more than the shifting weight.

As it slowed down, the stuck grid fins would have less authority (because there is not as much air flowing through them) and the RCS would have more authority. Makes sense that it looked more stable right as it neared a dead stop.

That makes sense, and the legs are inline with the fins. As soon as the legs start to deploy, what little airflow there is over the fins will be turbulent. I couldn't see it in the video, but likely to be RCS that killed the roll.
Transfer of momentum. When the legs deploy they transfer momentum slowing the roll. When that occurred the control system had enough authority to finish the roll dampening just before surface contact. It might have even survived a land landing.

If a stuck grid fin caused the roll I would say that the slowdown in speed had more to do with stopping the roll than any transfer of momentum from the leg deployment. At slow speed the reaction control thrusters could counteract the aerodynamic forces.

Nope. With the legs extended the "wider momentum" makes it much harder for the RCS fins to affect roll. This is another reason why the legs are deployed at the last second. Sure, lower speed helps in that it makes the stuck grid fins less effective, but note the timing of the leg deploy and the slowdown of the roll. It's all from the legs.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/05/2018 07:10 pm
I would wait for a real analysis of the first stage that will hence forth be named "Bob."

I like that name.

Personally, I don't see this stage flying again regardless of what Musk says, at least not as a whole unit. Maybe the tankage and interstage could be reused, but the rest will probably be scrapped and tested to see the effects of salt-water corrosion on flown hardware.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Hauerg on 12/05/2018 07:11 pm
I wonder if the control software could be modified so that when a fin freezes the fin on the opposite side can be placed in a position to dampen the action of the first one and then let the two other grids fins do all the work?  There wouldn't be as much control but if it can avoid a roll then there may be enough to get the booster down.

How do you propose to do that if all the fins are powered by the single pump?

Ouch.  I thought originally it was independent pumps but I guess it is one pump driving all four actuators.  Definitely nothing that can be done there without a redundant string.
Except for ejecting/blasting off all the grid fins. Which, of course introduce new failure modes nobody needs.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: sghill on 12/05/2018 07:12 pm
Based on the full landing video that Elon posted, looks like the leg deployment momentum shift had the most impact in reducing the roll. (like a spinning figure skater)

And it looks like the grid fins were locked in a position to increase the roll... So the RCS fought that roll all the way down.

If this were the 1950-60s, we'd be talking about the unbelievable skills of the pilot who wrestled the craft all the way to the ground and regained control at literally the last moment to soft land his aircraft intact....

Good job Major Tom!
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: leetdan on 12/05/2018 07:13 pm
GO craft are on the move, per redacted local surveillance resources.

Edit: GO Quest is underway heading offshore, after shuffling with GO Navigator.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Hauerg on 12/05/2018 07:13 pm
I would wait for a real analysis of the first stage that will hence forth be named "Bob."

I like that name.

Personally, I don't see this stage flying again regardless of what Musk says, at least not as a whole unit. Maybe the tankage and interstage could be reused, but the rest will probably be scrapped and tested to see the effects of salt-water corrosion on flown hardware.
The grid fins will flay again, since they are extremely expensive and it takes forever to make them IIRC.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Ronsmytheiii on 12/05/2018 07:13 pm
So how long until they ask about the landing at the post launch press conference?

(Drinking game, take a shot everytime they ask about it)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Johnnyhinbos on 12/05/2018 07:14 pm
So how long until they ask about the landing at the post launch press conference?

(Drinking game, take a shot everytime they ask about it)
First question, guaranteed...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Thorny on 12/05/2018 07:15 pm
There she blows..

Wow! Can a large enough ship get in that close to shore to recover the booster?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: niwax on 12/05/2018 07:16 pm
I wonder if the control software could be modified so that when a fin freezes the fin on the opposite side can be placed in a position to dampen the action of the first one and then let the two other grids fins do all the work?  There wouldn't be as much control but if it can avoid a roll then there may be enough to get the booster down.

How do you propose to do that if all the fins are powered by the single pump?

Ouch.  I thought originally it was independent pumps but I guess it is one pump driving all four actuators.  Definitely nothing that can be done there without a redundant string.
Except for ejecting/blasting off all the grid fins. Which, of course introduce new failure modes nobody needs.

They'd probably rather save the fins than give the stage the slight chance of returning without them. It's not like they're guaranteed to land the stage without control surfaces and those fins take ages to manufacture and can probably be reused.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/05/2018 07:16 pm
The grid fins will flay again, since they are extremely expensive and it takes forever to make them IIRC.

Oh yeah, those as well. Good point.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: TorenAltair on 12/05/2018 07:18 pm
I miss the old landing game  ;)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Oersted on 12/05/2018 07:23 pm
If a stuck grid fin caused the roll I would say that the slowdown in speed had more to do with stopping the roll than any transfer of momentum from the leg deployment. At slow speed the reaction control thrusters could counteract the aerodynamic forces.

Nope. With the legs extended the "wider momentum" makes it much harder for the RCS fins to affect roll. This is another reason why the legs are deployed at the last second. Sure, lower speed helps in that it makes the stuck grid fins less effective, but note the timing of the leg deploy and the slowdown of the roll. It's all from the legs.

It makes sense what you say, but we probably need to wait for an analysis of the telemetry before we can state so categorically what caused what.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: chrisking0997 on 12/05/2018 07:24 pm
So how long until they ask about the landing at the post launch press conference?

(Drinking game, take a shot everytime they ask about it)
First question, guaranteed...

lol....ol Chris G took that away
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: darkenfast on 12/05/2018 07:24 pm
There she blows..

Wow! Can a large enough ship get in that close to shore to recover the booster?

Back during the abort test (which landed a lot closer to shore), you could see a barge and crane further out, waiting for the capsule to be towed to them.  I expect (purely guessing, here), that a GO vessel will secure the stage before it can run aground or jam that leg underneath into something, and then a commercial barge and crane(s) will do the actual salvage.  The alternative is to tow the thing and then lift it in port.  This could be problematic with the port authorities.  I think it's in deep enough water right now for a smaller tug or GO vessel to get in there.  Tides and winds can be the enemy here.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Ronsmytheiii on 12/05/2018 07:24 pm
So how long until they ask about the landing at the post launch press conference?

(Drinking game, take a shot everytime they ask about it)
First question, guaranteed...

Ha, Chris G beats the spread.....
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mmeijeri on 12/05/2018 07:26 pm
The grid fins will flay again, since they are extremely expensive and it takes forever to make them IIRC.

The pump on the other hand may be grounded...   ;)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Ronsmytheiii on 12/05/2018 07:27 pm
Any chance of a successful landing had the ditch order not been given? Landing looks close to nominal.  Yes, on the the Ocean but still.....

There wasn't a "ditch order" the stage aims for a water impact, then moves over to the pad if conditions are good. aka fail safe.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/05/2018 07:28 pm
Does Falcon still have independent gas-generator nozzle actuation for the centre Merlin, or was that dumped in the move to the octaweb?

Dumped, on the first stage it was only ever available on the Falcon 1.

I thought also that Grasshopper rolled with vectorable gas generator exhaust .?.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: JSNH on 12/05/2018 07:34 pm
Go quest just left port from the info on the Port Canaveral ship tracker.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RoboGoofers on 12/05/2018 07:43 pm
Go quest just left port from the info on the Port Canaveral ship tracker.

It's not something they would plan on using often, but i expect they'd want to get out there quicker in the future, if only to lasso it and throw an anchor or two out. a couple of zodiacs on the beach, maybe, and a bunker for the crew to hide in.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mn on 12/05/2018 07:55 pm
I would wonder if the engineers might talk Musk out of adding a redundant pump if they can just make the one more robust. I seems like understanding and fixing the issue is better than redundancy for a non-mission critical system.

I wouldn't take any of Elon's tweets about the stage too seriously just yet.

The stage just landed, they didn't even look at it, nobody had time to fully analyze anything yet.

These are off the cuff responses, actual decisions will happen after thorough analysis and time to think.

As a general rule, don't take his tweets too seriously, especially when he's tweeting so close to the event that he obviously did not have the time to fully think it thru.

edit: fix typo
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Cheapchips on 12/05/2018 08:04 pm

On reusing the booster Hans had a wry smile and words to the effects of "I know Elon just tweeted about it but we'll see..."  ;D
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mn on 12/05/2018 08:12 pm
I would wonder if the engineers might talk Musk out of adding a redundant pump if they can just make the one more robust. I seems like understanding and fixing the issue is better than redundancy for a non-mission critical system.

I wouldn't take any of Elon's tweets about the stage too seriously just yet.

The stage just landed, they didn't even look at it, nobody had time to fully analyze anything yet.

These are off the cuff responses, actual decisions will happen after thorough analysis and time to think.

As a general rule, don't take his tweets too seriously, especially when he's tweeting so close to the event that he obviously did not have the time to fully think it thru.

edit: fix typo

(And just for fun, I'll argue against myself now)

It's possible that they have been seriously considering adding a 2nd pump, perhaps decided to hold off as everything was working, and now that they had a failure the tweet response can be immediate and well thought thru at the same time.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Hauerg on 12/05/2018 08:18 pm
At what point when you don't have complete control of your rocket flying back toward land does range safety kick in? While i'm sure they are happy they got their rocket back (albeit a little wet) I expect we will need to be asking some questions about whether the automated flight termination system worked as it was designed - and if it did - who didn't trigger a manual termination and why not? Dangerous as hell.
No.
All worked as planned.
No need to autodestruct when you are physically not able to reach land.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 08:20 pm
At what point when you don't have complete control of your rocket flying back toward land does range safety kick in? While i'm sure they are happy they got their rocket back (albeit a little wet) I expect we will need to be asking some questions about whether the automated flight termination system worked as it was designed - and if it did - who didn't trigger a manual termination and why not? Dangerous as hell.
No.
All worked as planned.
No need to autodestruct when you are physically not able to reach land.
... and still within the keep-out area cleared by the range.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Johnnyhinbos on 12/05/2018 08:25 pm
Coast Guard of Port Canaveral just issued a Securite call re a hazard to navigation off Port Canaveral. Homm... wonder what that is. (Couldn't tell because the details of the call are given on VHF channel 22A)


As a boater, I don't ever recall hearing a Securite for a rocket laying in the water...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vanoord on 12/05/2018 08:26 pm
Any chance of a successful landing had the ditch order not been given? Landing looks close to nominal.  Yes, on the the Ocean but still.....

The stage needs the grid fins to orientate it and give it lift as it falls, which carries it towards the landing pad.

With the fins inoperative, the stage doesn't have the lift and falls short of the landing pad by default.

Presumably the software is such that if the stage loses fin control, it re-targets to soft land in the ocean with a normal landing burn.

Why? Well, probably better than it fighting all the way down trying to get where it should be; and quite possibly because someone has thought this through and realised that burning up all propellants before hitting the water is a good idea from a pollution point of view.

As far as any specific intention in the programming to try and recover the core, the jury's out - but even if it experienced a RUD when it topped, that's would make finding four very expensive grid fins a whole lot easier.

Whether or not floating the stage in to Port Canaveral is a go-er is something the next 24 hours will show ;)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Johnnyhinbos on 12/05/2018 08:27 pm
Eagle is currently hailing GoQuest...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Devlin98 on 12/05/2018 08:33 pm
Eagle and Go Quest went to Channel 10.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Orbiter on 12/05/2018 08:34 pm
I am curious to see how exactly they'll approach bringing a rocket back into port that didn't land on an ASDS. Why not just fish it out, put it on OCISLY, and then take it back to port that way?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: envy887 on 12/05/2018 08:36 pm
This would hardly be the first time a rocket was floated into Port Canaveral alongside a ship.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Johnnyhinbos on 12/05/2018 08:36 pm
Eagle is currently hailing GoQuest...
And GoQuest responded and they switched from CH 16 to CH 10, which I can't monitor in Boston! Anyone down there with a VHF?


Oooh! So they have a line on it by the "nozzles" and need someone to get a photo to prove they got it first (salvage rights). Also mentioned that they have a sea anchor if needed.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mn on 12/05/2018 08:37 pm
I am curious to see how exactly they'll approach bringing a rocket back into port that didn't land on an ASDS. Why not just fish it out, put it on OCISLY, and then take it back to port that way?

And how exactly would you 'just' fish it out?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Michel Van on 12/05/2018 08:37 pm
i think that's goes into History as "The Day SpaceX went Kerbal..."
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kirghizstan on 12/05/2018 08:40 pm
I am curious to see how exactly they'll approach bringing a rocket back into port that didn't land on an ASDS. Why not just fish it out, put it on OCISLY, and then take it back to port that way?

And how exactly would you 'just' fish it out?


Put the crane on OCISLY


That is partially serious, but understand stability issues associated with sea state and that OCISLY's deck might not be able to handle the load
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Orbiter on 12/05/2018 08:41 pm
I am curious to see how exactly they'll approach bringing a rocket back into port that didn't land on an ASDS. Why not just fish it out, put it on OCISLY, and then take it back to port that way?

And how exactly would you 'just' fish it out?

Carefully :)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ellindsey on 12/05/2018 08:42 pm
I am curious to see how exactly they'll approach bringing a rocket back into port that didn't land on an ASDS. Why not just fish it out, put it on OCISLY, and then take it back to port that way?

Lifting the stage usually requires using a crane to attach a lifting fixture to the top of the rocket while it's vertical, then lifting the entire rocket with the crane.

Attaching the lifting fixture to the top of the rocket while the rocket is sideways bobbing in the water will be a challenge, and they don't have a crane handy that they can float out to sea to lift it with.

They'll probably have to kluge some kind of attachment to the rocket structure and then tow it to somewhere where they can get a crane to lift it out of the water.  I doubt the rocket will be reusable after this process.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vanoord on 12/05/2018 08:44 pm
The issue is going to be attaching the lifting cap (or similar) to the top of the stage.

Lifting it upside down shouldn't be a problem as there are good attachment points on the octaweb. But that's no use for getting it the right way up again to get the legs off.

With a bit of foresight, there should be a contingency plan for just this scenario - which should be well in progress by now.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: flyright on 12/05/2018 08:50 pm
This would hardly be the first time a rocket was floated into Port Canaveral alongside a ship.

Good point!

I've been wondering what the port officials reaction might be to a rocket being towed into the port.
Good that there are many prievious examples (though they were solids instead of liquids).
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Doesitfloat on 12/05/2018 08:57 pm
Just get the stage transportation truck and dollies. Tow the rocket to a boat launch. Treat it like a bass boat.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Oersted on 12/05/2018 08:57 pm
Monitoring Port Canaveral marine radio.

Just heard "they have a line on it by the "nozzles" and need someone to get a photo to prove they got it first."

(salvage rights). Also mentioned that they have a sea anchor if needed.

Did somebody else than SpaceX get to the rocket first!?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CJ on 12/05/2018 09:03 pm
Regarding adding a second pump and lines vs. making the present one more robust; for F9 operation, I agree with those above who say making the single pump more robust is better. However, there's probably more than F9 at play here; there's BFR to consider. IMHO, they might be going redundant for that (especially BFS) so it'd make sense to go that route now.

IMHO, the fact the F9 managed to survive supersonic loss of control and then touch down and end up intact is utterly astounding.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Johnnyhinbos on 12/05/2018 09:06 pm
Monitoring Port Canaveral marine radio.

Just heard "they have a line on it by the "nozzles" and need someone to get a photo to prove they got it first."

(salvage rights). Also mentioned that they have a sea anchor if needed.

Did somebody else than SpaceX get to the rocket first!?


Don't think so - I believe it's more of a formality in case someone claims they got to it first (somehow).

Boy though, wouldn't that be something if someone else claims salvage rights...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/05/2018 09:10 pm
You can't claim salvage rights on something that hasn't been officially abandoned at sea (this is the same reason that Spain keeps claiming treasure from Spanish wrecks that are centuries old). I 100% guarantee this booster has not been abandoned by SpaceX.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: AC in NC on 12/05/2018 09:11 pm
Just get the stage transportation truck and dollies. Tow the rocket to a boat launch. Treat it like a bass boat.

***snort*** Can you imagine backing up that big bastard?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: wardy89 on 12/05/2018 09:12 pm
Monitoring Port Canaveral marine radio.

Just heard "they have a line on it by the "nozzles" and need someone to get a photo to prove they got it first."

(salvage rights). Also mentioned that they have a sea anchor if needed.

Did somebody else than SpaceX get to the rocket first!?


Don't think so - I believe it's more of a formality in case someone claims they got to it first (somehow).

Boy though, wouldn't that be something if someone else claims salvage rights...

I might be wrong, but i was under the impression that space hardware because of ITAR regulations is exempt from normal marine salvage laws and remains property of the manufacturer?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/05/2018 09:13 pm
Marine traffic over the last 2 minutes

Its ~2 miles north of the port entry near bouys ?3,4,5,6?  Should be entering port mouth in 1-1/2 hours (someone said) But also there's word that "they won't let me put a line on it", waiting for Eagle to get in here from far out.  Someone else pointed out that there's a cruise ship set to leave soon.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/05/2018 09:15 pm
Monitoring Port Canaveral marine radio.

Just heard "they have a line on it by the "nozzles" and need someone to get a photo to prove they got it first."

(salvage rights). Also mentioned that they have a sea anchor if needed.

Did somebody else than SpaceX get to the rocket first!?


Don't think so - I believe it's more of a formality in case someone claims they got to it first (somehow).

Boy though, wouldn't that be something if someone else claims salvage rights...

I might be wrong, but i was under the impression that space hardware because of ITAR regulations is exempt from normal marine salvage laws and remains property of the manufacturer?

Under the Outer Space Treaty, anything launched into space remains the property of the nation that launched it into space, regardless of where it ends up if it falls back to Earth.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: 1 on 12/05/2018 09:21 pm
Monitoring Port Canaveral marine radio.

Just heard "they have a line on it by the "nozzles" and need someone to get a photo to prove they got it first."

(salvage rights). Also mentioned that they have a sea anchor if needed.

Did somebody else than SpaceX get to the rocket first!?


Don't think so - I believe it's more of a formality in case someone claims they got to it first (somehow).

Boy though, wouldn't that be something if someone else claims salvage rights...

I might be wrong, but i was under the impression that space hardware because of ITAR regulations is exempt from normal marine salvage laws and remains property of the manufacturer?

My understanding of maritime law is admittedly limited, but I don't think salvage rights apply here as the item is question is clearly not abandoned. As such, the only entity with a "right" to approach is whomever has a towing contract with SpaceX. I agree that this is more about formality, specifically formally showing intent to recover rather than abandon. Even if someone zipped out and got there first, I don't believe they'd have any legal claim to the booster.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/05/2018 09:24 pm
If a stuck grid fin caused the roll I would say that the slowdown in speed had more to do with stopping the roll than any transfer of momentum from the leg deployment. At slow speed the reaction control thrusters could counteract the aerodynamic forces.

Nope. With the legs extended the "wider momentum" makes it much harder for the RCS fins to affect roll. This is another reason why the legs are deployed at the last second. Sure, lower speed helps in that it makes the stuck grid fins less effective, but note the timing of the leg deploy and the slowdown of the roll. It's all from the legs.

It makes sense what you say, but we probably need to wait for an analysis of the telemetry before we can state so categorically what caused what.
What does Lars like to tell others when analyzing video feed "better keep your day job"... He now needs to take his own advice... ;)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: punder on 12/05/2018 09:27 pm
What was it they launched, again? Everything going okay with whatever it was?

 ???
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/05/2018 09:30 pm
What was it they launched, again? Everything going okay with whatever it was?

 ???
A-OK!
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: tonya on 12/05/2018 09:32 pm
You can't claim salvage rights on something that hasn't been officially abandoned at sea (this is the same reason that Spain keeps claiming treasure from Spanish wrecks that are centuries old). I 100% guarantee this booster has not been abandoned by SpaceX.

If I were Jeff Bezos, I'd still be so tempted to tweet that I was going fishing.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: eriblo on 12/05/2018 09:34 pm
Regarding adding a second pump and lines vs. making the present one more robust; for F9 operation, I agree with those above who say making the single pump more robust is better. However, there's probably more than F9 at play here; there's BFR to consider. IMHO, they might be going redundant for that (especially BFS) so it'd make sense to go that route now.

IMHO, the fact the F9 managed to survive supersonic loss of control and then touch down and end up intact is utterly astounding.
A single pump is likely the lightest solution but you can shift the failure probabilities by using smaller redundant pumps which would be more reliable except for the cases where the maximum torque is needed. A simple two pump example: twice the chance of a failure like today but grid fins then operating at half torque instead of failing competently completely  ::).
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vanoord on 12/05/2018 09:40 pm
1 (known) pump failure in 38 attempts (plus the water landings - perhaps a dozen more).

If the issue can be traced if/after the core is fished out, it may be possible to rectify the fault and keep flying with one pump - and accept a 1/100 or so probability of it happening again.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/05/2018 09:41 pm
Eagle:

I'm going to come around the buoy and get a line on it somehow and shackle it to my line and take it in somewhere.  <question from another vessel (GQ? who is also out there?))> My office gave me permission to put a line on it.


Me: I can't believe they're willing to approach with so little severe caution.  I can't believe you can just pull something so potentially energetic and seemingly unstable or at least in an unknown state into a busy port.  Unless maybe communications with it are so good that they were able to bleed pressure and safe it in the normal manner.  But then how can you vent the tank pressure without making it structurally vulnerable.?.

And then there's the legs.  Its seemingly all mariners coming up with a plan.  How are they gonna get them out of the way for passage into shallower water?

More from the radio:
"she's floating well"
"DIDN'T WILE E. COYOTE PRETTY MUCH BLOW THIS THEORY OUT OF THE WATER"
"who's coming?"
"Eagle, Searcher, and three of her little boats"
"We're just holding the line and drifting with it"
"S.W. corner of the rocket"
"Would you be comfortable with me approaching and passing me the line"
"Yes"
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: acsawdey on 12/05/2018 09:43 pm
Eagle:

I'm going to come around the buoy and get a line on it somehow and shackle it to my line and take it in somewhere.  <question from another vessel (GQ? who is also out there?))> My office gave me permission to put a line on it.


Me: I can't believe they're willing to approach with so little severe caution.  I can't believe you can just pull something so potentially energetic and seemingly unstable or at least in an unknown state into a busy port.  Unless maybe communications with it are so good that they were able to bleed pressure and safe it in the normal manner.  But then how can you vent the tank pressure without making it structurally vulnerable.?.

And then there's the legs.  Its seemingly all mariners coming up with a plan.  How are they gonna get them out of the way for passage into shallower water?

More from the radio:
"she's floating well"
"DIDN'T WILE E. COYOTE PRETTY MUCH BLOW THIS THEORY OUT OF THE WATER"
"who's coming?"
"Eagle, Searcher, and three of her little boats"
"We're just holding the line and drifting with it"
"S.W. corner of the rocket"
"Would you be comfortable with me approaching and passing me the line"
"Yes"

Elon tweeted that the flight computer was running after it fell over and that it completed the safing process. [OK, I must be misremembering because I can't find that tweet now. But see below for possibly the RP-1 tank venting.]

Also:

https://twitter.com/elonmusk/status/1070446975642812416 (https://twitter.com/elonmusk/status/1070446975642812416)

I think the blast of fire you see after it sets down in the water is from venting the fuel tank which must have had some RP-1 vapor and/or droplets which were ignited by something down by the engines. It seems too controlled to have been the tank springing a leak.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mlindner on 12/05/2018 09:45 pm
It's amazing watching the entire structure flex and bend from the torques being put on the grid finds and then the whole structure twist when it impacts the water but holds together! That's some incredible engineering!

I think most of the bending is actually the camera not being firmly enough attached to the stage. (due to G-forces)

No, the camera doesn't move with respect to the rocket body, only the fins twist.

Look again. Or point out where you see bending. The camera is certainly shaken loose in the water impact.

https://youtu.be/Esh1jHT9oTA?t=1351

T+7:30 You can see the whole rocket body flex and bend as the grid fins bend out of location compared to the rocket body.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: eriblo on 12/05/2018 09:52 pm
Eagle:

I'm going to come around the buoy and get a line on it somehow and shackle it to my line and take it in somewhere.  <question from another vessel (GQ? who is also out there?))> My office gave me permission to put a line on it.


Me: I can't believe they're willing to approach with so little severe caution.  I can't believe you can just pull something so potentially energetic and seemingly unstable or at least in an unknown state into a busy port.  Unless maybe communications with it are so good that they were able to bleed pressure and safe it in the normal manner.  But then how can you vent the tank pressure without making it structurally vulnerable.?.

And then there's the legs.  Its seemingly all mariners coming up with a plan.  How are they gonna get them out of the way for passage into shallower water?

More from the radio:
"she's floating well"
"DIDN'T WILE E. COYOTE PRETTY MUCH BLOW THIS THEORY OUT OF THE WATER"
"who's coming?"
"Eagle, Searcher, and three of her little boats"
"We're just holding the line and drifting with it"
"S.W. corner of the rocket"
"Would you be comfortable with me approaching and passing me the line"
"Yes"

Elon tweeted that the flight computer was running after it fell over and that it completed the safing process. [OK, I must be misremembering because I can't find that tweet now. But see below for possibly the RP-1 tank venting.]

Also:

[tweet]

I think the blast of fire you see after it sets down in the water is from venting the fuel tank which must have had some RP-1 vapor and/or droplets which were ignited by something down by the engines. It seems too controlled to have been the tank springing a leak.
Hans stated in the post-launch presser that it went trough the whole safing procedure and kept on communicating (intermittently only due to line of sight issues).
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: MattBaker on 12/05/2018 09:52 pm
In the video just posted by Musk on twitter it looks like the engines touch water, presumably shut down, stage starts tipping over and then there's a small fireball, what's up with that?

I presume the booster started venting its fuel and it somehow ignited? But first where would it ignite, looks like the engines are shut down at this point, can LOX or RP-1 just ignite of the hot smoke around it like that?

And second, is the stage really venting like two seconds after what would have been a landing if it'd be on the ground? Or is this another "well, that wasn't supposed to happen like that"? Or does it have an automatic "emergency vent" mode when it thinks it landed but starts tipping over to prevent a large explosion.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Stan-1967 on 12/05/2018 09:54 pm
I think today's events merit an edit of SpaceX's "How Not to Land an Orbital Rocket Booster" reel.  This landing can push the time to the 3 minute mark.

https://www.youtube.com/watch?v=bvim4rsNHkQ
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: speedevil on 12/05/2018 09:55 pm
Regarding adding a second pump and lines vs. making the present one more robust; for F9 operation, I agree with those above who say making the single pump more robust is better. However, there's probably more than F9 at play here; there's BFR to consider. IMHO, they might be going redundant for that (especially BFS) so it'd make sense to go that route now.

IMHO, the fact the F9 managed to survive supersonic loss of control and then touch down and end up intact is utterly astounding.
A single pump is likely the lightest solution but you can shift the failure probabilities by using smaller redundant pumps which would be more reliable except for the cases where the maximum torque is needed. A simple two pump example: twice the chance of a failure like today but grid fins then operating at half torque instead of failing competently.

Mass on the first stage is around a fifth penalty to payload for reusable flights.
If they are committed to launching a lot of Starlink in 2019, this may be an acceptable penalty.
Two small pumps mean you now have to dig into your control software and get it so that it is stable under both pressure conditions in the event of a failure.

Plus - as was raised by the other poster, now you can tear down the failed pump.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/05/2018 09:57 pm
Small boat to ?Eagle: "from the point we have it ~near the legs~ the line is very weak, you have to be very careful in towing it, its like 3/8" chain"

I'm not going to pull it in I'm just going to hold it here until everyone comes up with a plan"

"I hope just everybody stays safe out here this evening with this thing"

position: 28 24.3, 80 30.8

approximate quotes
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: freddo411 on 12/05/2018 10:00 pm
I was under the impression that the center engine had essentially zero roll control.   Am I wrong?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: speedevil on 12/05/2018 10:04 pm
I was under the impression that the center engine had essentially zero roll control.   Am I wrong?
Zero, not essentially zero as I understand it.
The legs popping out considerably slowed the stage roll.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 10:04 pm
I was under the impression that the center engine had essentially zero roll control.   Am I wrong?

You are correct. If you are parsing Elon's tweet, note that he said "engineS". The RCS is not the main engines, but they are tiny rocket engines responsible for roll control in this scenario.

The grid fins were stuck in a position that increased roll, and the RCS was fighting them all the way down.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/05/2018 10:05 pm
In the video just posted by Musk on twitter it looks like the engines touch water, presumably shut down, stage starts tipping over and then there's a small fireball, what's up with that?

I presume the booster started venting its fuel and it somehow ignited? But first where would it ignite, looks like the engines are shut down at this point, can LOX or RP-1 just ignite of the hot smoke around it like that?

And second, is the stage really venting like two seconds after what would have been a landing if it'd be on the ground? Or is this another "well, that wasn't supposed to happen like that"? Or does it have an automatic "emergency vent" mode when it thinks it landed but starts tipping over to prevent a large explosion.

Yep, RP-1 fireball right after splashing down, but before tipping completely over, that would be the venting fuel. Presumably something was hot enough to ignite it.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: martin_nv on 12/05/2018 10:07 pm
Does anyone know how far ahead/behind the Dragon is in relation to the station? There is a station sighting opportunity here tonight and clear skies so I'm hoping to see the Dragon as well.

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/05/2018 10:08 pm
https://twitter.com/elonmusk/status/1070446975642812416 (https://twitter.com/elonmusk/status/1070446975642812416)

I think the blast of fire you see after it sets down in the water is from venting the fuel tank which must have had some RP-1 vapor and/or droplets which were ignited by something down by the engines. It seems too controlled to have been the tank springing a leak.

It is, look at it frame by frame and you'll see how there is a release from the lower third of the stage, and this is the vapor or propellant that ignites.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: MattBaker on 12/05/2018 10:14 pm
So the stage vents the RP-1 in a way where it can ignite, which as far as I know RP-1 is like diesel where it has to be atomised to ignite? I guess a vent is like an oversized spray bottle but...well, seems funny to me that a safety feature is expelling your fuel in a way where it can blow up.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: matthewkantar on 12/05/2018 10:17 pm
So the stage vents the RP-1 in a way where it can ignite, which as far as I know RP-1 is like diesel where it has to be atomised to ignite? I guess a vent is like an oversized spray bottle but...well, seems funny to me that a safety feature is expelling your fuel in a way where it can blow up.

Not blow up. Burn up.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: eriblo on 12/05/2018 10:17 pm
I was under the impression that the center engine had essentially zero roll control.   Am I wrong?
You are correct to first order, but if you are not spinning exactly around the long axis you can get a roll-canceling tangential component (preferably you should have TVC actuation faster than the rate of rotation). A really advanced control system would first initiate/increase the axis offset and then gimbal slightly sideways, all while compensating for control coupling and the failed grid fins as well as steering the stage to a soft landing using a minimum thrust larger than the stage weight - that would be impressive indeed :o
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: acsawdey on 12/05/2018 10:23 pm
So the stage vents the RP-1 in a way where it can ignite, which as far as I know RP-1 is like diesel where it has to be atomised to ignite? I guess a vent is like an oversized spray bottle but...well, seems funny to me that a safety feature is expelling your fuel in a way where it can blow up.

Not blow up. Burn up.

To be fair, normally the stage is shaken by the landing, not stirred by an out-of-controlled spin.

You can see a white cloud jetting from the vent location near the top of the fuel tank. It gets partway down before igniting.

I think there might have been more RP-1 vapor and droplets in the vent than usual. But they do start venting the stage with seconds of touchdown; on normal RTLS landings it's obvious because 2 opposing gas jet nozzles vent all the remaining nitrogen.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: andrewsdanj on 12/05/2018 10:23 pm
I was under the impression that the center engine had essentially zero roll control.   Am I wrong?
You are correct to first order, but if you are not spinning exactly around the long axis you can get a roll-canceling tangential component (preferably you should have TVC actuation faster than the rate of rotation). A really advanced control system would first initiate/increase the axis offset and then gimbal slightly sideways, all while compensating for control coupling and the failed grid fins as well as steering the stage to a soft landing using a minimum thrust larger than the stage weight - that would be impressive indeed :o

Also don't forget the grid fins are aero devices, control authority roughly goes with dynamic pressure, so density and the square of velocity. The roll moment from the grid fins would be dropping right through the landing burn, until such a point that the RCS wins. At touchdown the grid fins are purely decorative ;-)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: speedevil on 12/05/2018 10:25 pm
So the stage vents the RP-1 in a way where it can ignite, which as far as I know RP-1 is like diesel where it has to be atomised to ignite? I guess a vent is like an oversized spray bottle but...well, seems funny to me that a safety feature is expelling your fuel in a way where it can blow up.
It is moderately hard to make a vent in a liquid/gas tank that will always output either liquid or gas, when the tank is tipped.
It's likely that it would exhaust a mixture of gas/liquid in a flammable mist if the liquid is only partially or intermittently covering the intake.
Adding mass to cope with landing in unusual attitudes where the stage is assumed to be destroyed isn't worth it.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: acsawdey on 12/05/2018 10:25 pm
I was under the impression that the center engine had essentially zero roll control.   Am I wrong?
You are correct to first order, but if you are not spinning exactly around the long axis you can get a roll-canceling tangential component (preferably you should have TVC actuation faster than the rate of rotation). A really advanced control system would first initiate/increase the axis offset and then gimbal slightly sideways, all while compensating for control coupling and the failed grid fins as well as steering the stage to a soft landing using a minimum thrust larger than the stage weight - that would be impressive indeed :o

Not out of the question that it could have in fact done this -- in one of the videos you can see that there was a large yaw motion just before the legs deployed and some large TVC deflection along with it.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/05/2018 10:29 pm
How does a single engine counter roll?  This was a single-engine landing, not a three-engine landing, unless I'm mistaken.

Single-engine landing burns allow for more control authority

A single M1d engine provides no roll control authority.
If the engine control system is taking the grid fins into account, then I think even a single engine can do it.

-----
ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/05/2018 10:30 pm
Earlier marine radio would have me believing that they're 2 miles north of the port but that's not what I see when I plot the lat/lon.  And that seems to be confirmed by the buoy numbers they're near.

More audio (semi-quotes)-

"We have a line on it N. of 5 &6 and I'm going to spin Eagle around and hold it north of the channel"

"...Hang out overnight, operations manager is coming from Ft. Lauderdale"

"Going to stay here where its 3-4'.  When I got out by its original position it was 6-8'  "

"We'll let you know the plan when we've talked it over with the operations manager ~ maybe, we'll see"  (my interpretation, sounds like that's hours away, maybe tomorrow)

Planning for operations manager: "not a good plan to transfer him in this sea state.  ~~platform not good~~ RIB to stern probably not a good idea.  ...Ladder, scurry up the side"

Brevard county boat was on station with blue lights and CG small boat came in and relieved them.  Seems to be only there for observation.

Coast Guard small boat to Eagle once CG came in and saw the layout: "What is the plan, are you going to stay on scene until first light?"  Eagle: Let's go to Ch. 22 (I don't have access to hear what was said there)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: eriblo on 12/05/2018 10:36 pm
I was under the impression that the center engine had essentially zero roll control.   Am I wrong?
You are correct to first order, but if you are not spinning exactly around the long axis you can get a roll-canceling tangential component (preferably you should have TVC actuation faster than the rate of rotation). A really advanced control system would first initiate/increase the axis offset and then gimbal slightly sideways, all while compensating for control coupling and the failed grid fins as well as steering the stage to a soft landing using a minimum thrust larger than the stage weight - that would be impressive indeed :o

Not out of the question that it could have in fact done this -- in one of the videos you can see that there was a large yaw motion just before the legs deployed and some large TVC deflection along with it.
Yeah, quite possible. We know that they have by rad-hard rocket standards obscene processing power and are updating the state-space and running control and trajectory optimization in real time. I don't think they just got lucky :)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/05/2018 10:39 pm
So the stage vents the RP-1 in a way where it can ignite, which as far as I know RP-1 is like diesel where it has to be atomised to ignite? I guess a vent is like an oversized spray bottle but...well, seems funny to me that a safety feature is expelling your fuel in a way where it can blow up.
It is moderately hard to make a vent in a liquid/gas tank that will always output either liquid or gas, when the tank is tipped.
It's likely that it would exhaust a mixture of gas/liquid in a flammable mist if the liquid is only partially or intermittently covering the intake.
Adding mass to cope with landing in unusual attitudes where the stage is assumed to be destroyed isn't worth it.

Slosh, Centerfugeness could raise the fuel level quite a bit beyond normal.

Does anyone remember what the sea state was when the previous non-kaboom F9 water landing was?  I'm hypothesizing that in calm seas when the whole cylinder slaps the water at once we get kaboom but in high seas (6-8' where it flopped) it has a more gradual entry to the water thus nonkaboom.

Now best guess is that it'll be ~8pm ET when the operations manager gets there.

Correction to earlier, its sheriff that's there and CG that went home.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: eeergo on 12/05/2018 10:43 pm

It was ice and it came off the booster at the lower end, not where the fins are.


No, go to the launch video and watch starting around T+5:50. The perspective is messing with you but you can clearly see that it is a small ring up close, not a bigger ring farther away from the camera. There's frames where you can see it in front of the gridfin, i.e. between the camera and the gridfin.


It may have been ice, no comment on that.  Just that it was from the area around the gridfins and actually bumped into the one on the left before it started floating up and away.


That looks like it's coming from a feedthrough (also supported by its round shape) on the interstage, probably the one highlighted in the attached image.


On the other hand, why the conditions in this flight allowed for it to be detached, as opposed to in other (daylight) missions? It also seemed the gridfins deployed "hiccuping" rather than slowly but smoothly like in previous flights...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mlindner on 12/05/2018 10:47 pm
Earlier marine radio would have me believing that they're 2 miles north of the port but that's not what I see when I plot the lat/lon.  And that seems to be confirmed by the buoy numbers they're near.

More audio (semi-quotes)-

"We have a line on it N. of 5 &6 and I'm going to spin Eagle around and hold it north of the channel"

"...Hang out overnight, operations manager is coming from Ft. Lauderdale"

"Going to stay here where its 3-4'.  When I got out by its original position it was 6-8'  "

"We'll let you know the plan when we've talked it over with the operations manager ~ maybe, we'll see"  (my interpretation, sounds like that's hours away, maybe tomorrow)

Planning for operations manager: "not a good plan to transfer him in this sea state.  ~~platform not good~~ RIB to stern probably not a good idea.  ...Ladder, scurry up the side"

Brevard county boat was on station with blue lights and CG small boat came in and relieved them.  Seems to be only there for observation.

Coast Guard small boat to Eagle once CG came in and saw the layout: "What is the plan, are you going to stay on scene until first light?"  Eagle: Let's go to Ch. 22 (I don't have access to hear what was said there)

Can anyone give a link to where this can be listened to live on the web?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: martin_nv on 12/05/2018 10:50 pm
Quote
Can anyone give a link to where this can be listened to live on the web?
https://www.broadcastify.com/listen/feed/21054

Seems kind of quiet now though.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CraigLieb on 12/05/2018 11:52 pm
I miss the old landing game  ;)
Water squares would have to be added to the LZ1 grid
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: freddo411 on 12/05/2018 11:55 pm
I was under the impression that the center engine had essentially zero roll control.   Am I wrong?
You are correct to first order, but if you are not spinning exactly around the long axis you can get a roll-canceling tangential component (preferably you should have TVC actuation faster than the rate of rotation). A really advanced control system would first initiate/increase the axis offset and then gimbal slightly sideways, all while compensating for control coupling and the failed grid fins as well as steering the stage to a soft landing using a minimum thrust larger than the stage weight - that would be impressive indeed :o

I thought there might be some second order effects.   Watching the stage it looked like it did retard the rotation a bit
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/06/2018 12:50 am
"The man" is being brought out to Eagle on a fast boat now, to approach from the side in a few minutes.  Hopefully they have a spot for him to sleep because i don't see much opportunity to make progress until the sun comes up. There seems to be more of the conversation going on on alternate channels recently but maybe perking up on the main channel that we can hear through the internets.

edit: Onboard now.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Okie_Steve on 12/06/2018 01:05 am
Watching the stage it looked like it did retard the rotation a bit

Some one definitely deserves a gold star for the control system robustness.

Edit  - typo
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: rickl on 12/06/2018 01:14 am
Watching the stage it looked like it did retard the rotation a bit

Some one definitely deserves a gold star for the control system robustness.


I have to say, that was a hell of a good landing for a "failure".
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Scylla on 12/06/2018 02:13 am
Changed my link to this video on the update thread to the actual producer, Kerbal Space Academy.

Question: Does anybody know why they have Nasaspacflight.com in the corner of the screen as well as their own?
https://youtu.be/9XMfhKxwo2c
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: rocketguy101 on 12/06/2018 02:14 am
I am curious to see how exactly they'll approach bringing a rocket back into port that didn't land on an ASDS. Why not just fish it out, put it on OCISLY, and then take it back to port that way?

And how exactly would you 'just' fish it out?


Put the crane on OCISLY


That is partially serious, but understand stability issues associated with sea state and that OCISLY's deck might not be able to handle the load

There are such things as crane barges...my son worked on one when he was in the Army Reserves (he was a Watercraft Engineer) ... they trained to lift some hairy stuff in non-ideal sea states
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: deruch on 12/06/2018 02:22 am
Changed my link to this video on the update thread to the actual producer, Kerbal Space Academy.

Question: Does anybody know why they have Nasaspacflight.com in the corner of the screen as well as their own?
https://www.youtube.com/watch?v=9XMfhKxwo2c

He and ChrisG were live streaming the launch/landing together, ChrisG "on behalf" of NSF.  One of the voices you hear in that video is Chris'. 

https://twitter.com/ChrisG_NSF/status/1070358919833374721
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: spacenut on 12/06/2018 02:26 am
Is the Dragon ok on its way to the ISS?  I know the solar panels deployed.  It was the primary purpose of the flight. 
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RotoSequence on 12/06/2018 03:48 am
It was the leg deployment that did most of the work.  And the same change in rotational inertial would have made it harder for the control system.

This assertion is contradicted by the onboard footage. The roll is mostly nulled by the time the legs begin to deploy.

https://twitter.com/elonmusk/status/1070399755526656000
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CJ on 12/06/2018 03:59 am
Musk's tweet was;

Quote
Engines stabilized rocket spin just in time, enabling an intact landing in water! Ships en route to rescue Falcon.

My question is, how can a single engine landing burn (center engine) null a spin? I'm not claiming it didn't (the video makes it clear it did) I'm just trying to understand how a center engine could generate the needed torque. 
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/06/2018 04:11 am
Musk's tweet was;

Quote
Engines stabilized rocket spin just in time, enabling an intact landing in water! Ships en route to rescue Falcon.

My question is, how can a single engine landing burn (center engine) null a spin? I'm not claiming it didn't (the video makes it clear it did) I'm just trying to understand how a center engine could generate the needed torque.
If the stage was in vacuum, then it'd be impossible.

If there are aerodynamic forces, especially way out on the far end, then absolutely they can, but I am floored that they did in practice.

Not only is it difficult to control roll, the stage was at such an extreme state that all assumptions that hold "near nominal" such as small angle approximations and such - all those were out the window.

This is one of the most amazing space videos ever!

-----
ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mlindner on 12/06/2018 04:20 am
It was the leg deployment that did most of the work.  And the same change in rotational inertial would have made it harder for the control system.

This assertion is contradicted by the onboard footage. The roll is mostly nulled by the time the legs begin to deploy.

https://twitter.com/elonmusk/status/1070399755526656000

I don't really agree with that, the instant the legs pop out the roll basically stops.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: zubenelgenubi on 12/06/2018 04:34 am
If this were the 1950-60s, we'd be talking about the unbelievable skills of the pilot who wrestled the craft all the way to the ground and regained control at literally the last moment to soft land his aircraft intact....

Good job Major Tom!

Dare I say, the avionics aboard B1050.1 has "The Right Stuff"?!

Maybe this "black box" could be Time magazine's Computer of the Year?  (Is Time still relevant?)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RotoSequence on 12/06/2018 04:54 am
I don't really agree with that, the instant the legs pop out the roll basically stops.

The tracking shots all show that the vehicle's roll rate visibly decreases well before the legs pop out. The leg deployment helped, but the engine clearly did much, or even most, of the work first.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: DigitalMan on 12/06/2018 04:57 am
I don't really agree with that, the instant the legs pop out the roll basically stops.

The tracking shots all show that the vehicle's roll rate visibly decreases well before the legs pop out. The leg deployment helped, but the engine clearly did much, or even most, of the work first.

One of the things I was pondering was this:

High pressure helium is used to extend the legs, no?  Is it possible the release of the high pressure helium during leg deploy could have an effect on the MOI before it noticeably moves the legs?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Comga on 12/06/2018 05:09 am
Musk's tweet was;

Quote
Engines stabilized rocket spin just in time, enabling an intact landing in water! Ships en route to rescue Falcon.

My question is, how can a single engine landing burn (center engine) null a spin? I'm not claiming it didn't (the video makes it clear it did) I'm just trying to understand how a center engine could generate the needed torque. 

This was answered farther back in the thread
Musk is referring to the cold nitrogen thrusters as "engines".
There is protracted debate about when a single, on-axis engine can induce torque to increase or decrease roll rates, but the basic answer is it can't do much, and certainly didn't for this fist stage.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: catdlr on 12/06/2018 05:13 am
I don't really agree with that, the instant the legs pop out the roll basically stops.

The tracking shots all show that the vehicle's roll rate visibly decreases well before the legs pop out. The leg deployment helped, but the engine clearly did much, or even most, of the work first.

One of the things I was pondering was this:

High pressure helium is used to extend the legs, no?  Is it possible the release of the high pressure helium during leg deploy could have an effect on the MOI before it noticeably moves the legs?

Here's my question...If the stage knows it's aborting a pad landing to land on the ocean, why then lower the legs at all?  Would it then make lifting onto a barge eaiser with the legs connected to the stage?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RotoSequence on 12/06/2018 05:28 am
Musk's tweet was;

Quote
Engines stabilized rocket spin just in time, enabling an intact landing in water! Ships en route to rescue Falcon.

My question is, how can a single engine landing burn (center engine) null a spin? I'm not claiming it didn't (the video makes it clear it did) I'm just trying to understand how a center engine could generate the needed torque. 

This was answered farther back in the thread
Musk is referring to the cold nitrogen thrusters as "engines".
There is protracted debate about when a single, on-axis engine can induce torque to increase or decrease roll rates, but the basic answer is it can't do much, and certainly didn't for this fist stage.

Its always possible I'm simply overrating my interpretation of the Mark 1 eyeball, so you could be right. It could also be that the vehicle's quick rotation is obliterating the visibility of the cold gas plumes, but it certainly doesn't look very much like previous large "firings" of their nitrogen RCS thrusters.

https://www.youtube.com/watch?v=4cvGGxTsQx0
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/06/2018 05:35 am
I don't really agree with that, the instant the legs pop out the roll basically stops.

The tracking shots all show that the vehicle's roll rate visibly decreases well before the legs pop out. The leg deployment helped, but the engine clearly did much, or even most, of the work first.

One of the things I was pondering was this:

High pressure helium is used to extend the legs, no?  Is it possible the release of the high pressure helium during leg deploy could have an effect on the MOI before it noticeably moves the legs?

Here's my question...If the stage knows it's aborting a pad landing to land on the ocean, why then lower the legs at all?  Would it then make lifting onto a barge eaiser with the legs connected to the stage?

Those legs create quite a bit of drag when.pressed under water as the stage is tilting and falling over, possibly enough to slow the falling stage down enough to prevent loss of structural integrity on splashdown. Only 2 stages survived their water landing up 2 date.  Both had legs deployed.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Nomadd on 12/06/2018 05:35 am

Here's my question...If the stage knows it's aborting a pad landing to land on the ocean, why then lower the legs at all?  Would it then make lifting onto a barge eaiser with the legs connected to the stage?
It might allow the legs to take some of the impact instead of the engines taking it all.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: catdlr on 12/06/2018 05:49 am

Here's my question...If the stage knows it's aborting a pad landing to land on the ocean, why then lower the legs at all?  Would it then make lifting onto a barge eaiser with the legs connected to the stage?
It might allow the legs to take some of the impact instead of the engines taking it all.

Great answers:  Thanks CorvusCorax and Nomadd.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/06/2018 06:26 am
Its always possible I'm simply overrating my interpretation of the Mark 1 eyeball, so you could be right. It could also be that the vehicle's quick rotation is obliterating the visibility of the cold gas plumes, but it certainly doesn't look very much like previous large "firings" of their nitrogen RCS thrusters.

https://www.youtube.com/watch?v=4cvGGxTsQx0

Yes, I think you are overrating your mark 1 eyeball. The light conditions are different - and the background. In the video there, note how much lighter the RCS plume looks against the ocean background... Almost like the sky color would be? And then look again at the tracking footage that Elon tweeted. Against a sky background.

Another point which may explain the RCS plume being less visible at touchdown might be that it actually ran out... or almost did. I bet this landing used up more then the average nitrogen gas.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: woods170 on 12/06/2018 08:21 am
Frankly, I'm surprised the AFTS didn't terminate and it still executed a soft landing off shore.

AFTS is saved before the entry burn begins. AFTS is for ascent only. Why do you think the initial aiming point for landing is out to sea?
Exactly because AFTS is not active during entry and landing.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: niwax on 12/06/2018 10:21 am
Frankly, I'm surprised the AFTS didn't terminate and it still executed a soft landing off shore.

AFTS is saved before the entry burn begins. AFTS is for ascent only. Why do you think the initial aiming point for landing is out to sea?
Exactly because AFTS is not active during entry and landing.

AFTS is also pointless on landing, it just makes sure you scatter debris over the entire launch site. It works when your velocity vector is pointing away from the launchpad.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kevinof on 12/06/2018 10:31 am
I also think the optics of even a controlled termination is far worse than an intact stage gently landing on the water intact.

If you're going to have a failure, make it a good one.

Frankly, I'm surprised the AFTS didn't terminate and it still executed a soft landing off shore.

AFTS is saved before the entry burn begins. AFTS is for ascent only. Why do you think the initial aiming point for landing is out to sea?
Exactly because AFTS is not active during entry and landing.

AFTS is also pointless on landing, it just makes sure you scatter debris over the entire launch site. It works when your velocity vector is pointing away from the launchpad.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/06/2018 10:33 am
Frankly, I'm surprised the AFTS didn't terminate and it still executed a soft landing off shore.

AFTS is saved before the entry burn begins.

It is safed *after* the entry burn.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: MaxTeranous on 12/06/2018 10:47 am
Frankly, I'm surprised the AFTS didn't terminate and it still executed a soft landing off shore.

AFTS is saved before the entry burn begins.

It is safed *after* the entry burn.

If the entry burn fails, the stage breaks apart anyway doesn't it ?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CraigLieb on 12/06/2018 11:01 am
If this were the 1950-60s, we'd be talking about the unbelievable skills of the pilot who wrestled the craft all the way to the ground and regained control at literally the last moment to soft land his aircraft intact....

Good job Major Tom!

Dare I say, the avionics aboard B1050.1 has "The Right Stuff"?!

Maybe this "black box" could be Time magazine's Computer of the Year?  (Is Time still relevant?)
It’s the people that designed and implemented the control strategy you can recognize. Three cheers for the dedicated team of software and hardware designers that created this amazing vehicle and system.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Step55 on 12/06/2018 11:44 am
From "the camera that shall not be named", looks like they are loading some equipment onto OCISLY. Just saw them load to pallet sized objects onto the deck with the small crane.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jpo234 on 12/06/2018 11:55 am
If this were the 1950-60s, we'd be talking about the unbelievable skills of the pilot who wrestled the craft all the way to the ground and regained control at literally the last moment to soft land his aircraft intact....

Good job Major Tom!

Dare I say, the avionics aboard B1050.1 has "The Right Stuff"?!

Maybe this "black box" could be Time magazine's Computer of the Year?  (Is Time still relevant?)
It’s the people that designed and implemented the control strategy you can recognize. Three cheers for the dedicated team of software and hardware designers that created this amazing vehicle and system.

That would be Lars Blackmore (http://www.larsblackmore.com/)'s team.

https://twitter.com/larsblackmore/status/1070459490867142656

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: quagmire on 12/06/2018 12:21 pm
I am surprised there wasn't a plan in place to recover a booster after a water landing. Especially after the 1st stage that survived its intentional water landing, but had to be destroyed. One would think a plan would have been made on how to recover a booster bobbing in the water after they had to destroy that one.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: edzieba on 12/06/2018 12:32 pm
After the previous 'water landing' (B1032) that was successful but could not be recovered due to booster safety, I wonder if some splashdown-specific code was added (or even some minor hardware mods) to allow for the booster to reliably safe itself in the event of a splashdown. Approach to the booster seems to have been more blase than B1032, though it could just be that its presence near a major port and waterway (and proximity to land, and floating along the cost uncontrolled) was deemed as more of a hazard than approaching it with manned craft.
Dare I say, the avionics aboard B1050.1 has "The Right Stuff"?!

Maybe this "black box" could be Time magazine's Computer of the Year?  (Is Time still relevant?)
With the spin arrested by the leg deployment, and the leg pneumatic cylinders (and legs themselves) being made of CF, "Inanimate Carbon Rod" is still in the running!
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: woods170 on 12/06/2018 12:38 pm
Frankly, I'm surprised the AFTS didn't terminate and it still executed a soft landing off shore.

AFTS is saved before the entry burn begins.

It is safed *after* the entry burn.

I looked it up and you are correct. But, that still leaves the stage without AFTS after the initial aiming point has been established (via the entry burn and assumed ballistic entry from that point forward).

In short: by the time the the flight computer senses that the grid fins are not responding there is no active AFTS present to trigger a self-destruct.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: SciNews on 12/06/2018 12:39 pm
Hans Koenigsmann, SpaceX Vice President of Mission Assurance, about the anomaly
https://www.youtube.com/watch?v=SreNDDNZIG4
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RoboGoofers on 12/06/2018 12:48 pm
I think the anti slosh baffles had a lot to do with stopping the spin.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: LouScheffer on 12/06/2018 12:56 pm
It was the leg deployment that did most of the work.  And the same change in rotational inertial would have made it harder for the control system.
This assertion is contradicted by the onboard footage. The roll is mostly nulled by the time the legs begin to deploy.
I don't really agree with that, the instant the legs pop out the roll basically stops.
Both assertions are true.  Using this copy of the video (https://www.youtube.com/watch?v=nq3T_zPXOSE), we can use the time the shadow passes the tip of the left fin to measure the rotation rate.  Times are measured as youtube time + frames.
1:47 + 15/30
1:49 + 14/30
1:51 + 13/30
1:53 + 17/30
1:55 + 24/30
1:58 + 3/30
2:00 + 19/30
2:03 + 13/30
2:06 + 25/30
----- Legs come out
then about 1/4 more turn in 4 seconds.

So the roll rate was dropped from 1+29/30 (1.966) seconds per turn to 3+12/30 (3.40) seconds per turn before the legs came out, and was decreasing quite quickly. (By extrapolation, the next turn would have taken about 4 seconds.) But the legs also had a big effect, reducing the remaining roll rate by a factor 2-4.

EDIT: fix typo in last time.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/06/2018 12:56 pm
There's a lot of marine radio traffic involving our ships but I don't have time to listen and transcribe as I did last night.  Anyone?

https://www.broadcastify.com/listen/feed/21054/web (https://www.broadcastify.com/listen/feed/21054/web)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: envy887 on 12/06/2018 12:57 pm
Latest Elon tweet update-

"Pump is single string. Some landing systems are not redundant, as landing is considered ground safety critical, but not mission critical. Given this event, we will likely add a backup pump & lines."

Block 5.1

They have already made other changes to Block 5, like the new COPVs. Don't expect a new block yet.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: rsdavis9 on 12/06/2018 01:25 pm
Is the grid fin hydraulic motor powered by an electric motor?
I thought at first they used a hydraulic reservoir with gas pressure.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/06/2018 01:31 pm
I don't know whether the power source is electric or something else but I know that its no longer operated by a pressurized reservoir and the fluid disposed of overboard.  They're using a closed loop system with a pump now and have been for a long time, likely soon after they ran out of fluid on one of the early landings which was about the time that it became apparent that grid fins were getting the job done and it was worth investing more in them.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/06/2018 01:35 pm
It was the leg deployment that did most of the work.  And the same change in rotational inertial would have made it harder for the control system.
This assertion is contradicted by the onboard footage. The roll is mostly nulled by the time the legs begin to deploy.
I don't really agree with that, the instant the legs pop out the roll basically stops.
Both assertions are true.  Using this copy of the video (https://www.youtube.com/watch?v=nq3T_zPXOSE), we can use the time the shadow passes the tip of the left fin to measure the rotation rate.  Times are measured as youtube time + frames.
1:47 + 15/30
1:49 + 14/30
1:51 + 13/30
1:53 + 17/30
1:55 + 24/30
1:58 + 3/30
2:00 + 19/30
2:03 + 13/30
2:66 + 25/30
----- Legs come out
then about 1/4 more turn in 4 seconds.

So the roll rate was dropped from 1+29/30 (1.966) seconds per turn to 3+12/30 (3.40) seconds per turn before the legs came out, and was decreasing quite quickly. (By extrapolation, the next turn would have taken about 4 seconds.) But the legs also had a big effect, reducing the remaining roll rate by a factor 2-4.

The difference between engine roll cancellation and leg-deploy is that the legs are a one-time thing, and can only take out a fixed fraction of the roll (the ratio of the moments of inertia) - not zero it.

The engine, as long as it continues to fire, takes out spin at a fixed rate, and doesn't slow down towards the end.

The legs helped at the end, for sure, but that's the extent of it.  It might also be that by enlarging the perpendicular moments of inertia, the on-axis engine was able to get more "grip" for canceling axial rotation, something that some poster above found baffling (and rightly so)

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: freda on 12/06/2018 01:46 pm
In a rare case, at this moment, Port Canaveral Webcam is pointed at OCISLY at dock. I see no nearby activity; so I assume the booster remains slightly offshore, secured by the tug?  Waiting...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: flyright on 12/06/2018 01:51 pm
Go Quest is drifting south of the Channel according to an update they just gave the Coast Guard Sounds like they are meeting another ship, possibly "Pacific Talent".

Edit. "Pacific Talent" . appears to be a Bulk Carrier and Go Quest was being advised they were anchoring nearby. Probably unrelated to the recovery.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Hauerg on 12/06/2018 01:52 pm
Frankly, I'm surprised the AFTS didn't terminate and it still executed a soft landing off shore.

AFTS is saved before the entry burn begins.

It is safed *after* the entry burn.

I looked it up and you are correct. But, that still leaves the stage without AFTS after the initial aiming point has been established (via the entry burn and assumed ballistic entry from that point forward).

In short: by the time the the flight computer senses that the grid fins are not responding there is no active AFTS present to trigger a self-destruct.
Not needed since the booster cannot reach the pad, it needs to be working ok to GET OVER THERE.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/06/2018 02:02 pm
In a rare case, at this moment, Port Canaveral Webcam is pointed at OCISLY at dock. I see no nearby activity; so I assume the booster remains slightly offshore, secured by the tug?  Waiting...

Position as reported by Go Quest 10 minutes ago;

edit: Where they were last night the water depth was 39-42 feet.  Now if they are south of the channel(?) it may be ~3 feet more (give or take tide).  Can someone refresh me on leg length please?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: flyright on 12/06/2018 02:03 pm
There's a lot of marine radio traffic involving our ships but I don't have time to listen and transcribe as I did last night.  Anyone?

https://www.broadcastify.com/listen/feed/21054/web (https://www.broadcastify.com/listen/feed/21054/web)

I'm listening, but not making much sense of the transmissions. The Coast Guard is advising fishing vessels to remain more than 1/2 mile from the booster recovery operations which are apparently south of the channel along with Go Quest.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/06/2018 02:10 pm
Frankly, I'm surprised the AFTS didn't terminate and it still executed a soft landing off shore.

AFTS is saved before the entry burn begins.

It is safed *after* the entry burn.

I looked it up and you are correct. But, that still leaves the stage without AFTS after the initial aiming point has been established (via the entry burn and assumed ballistic entry from that point forward).

In short: by the time the the flight computer senses that the grid fins are not responding there is no active AFTS present to trigger a self-destruct.


True. I guess I was mostly surprised that the landing burn was actually initiated given the high roll rate and no way of making it to the desired landing point any more, but I guess there is good logic in burning off as much remaining RP-1 as possible before ocean impact and all that.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mlindner on 12/06/2018 02:12 pm
I think the anti slosh baffles had a lot to do with stopping the spin.

Anti slosh baffles only inhibit accelerations, they don't inhibit velocities, because there is no sloshing going on. In fact anti-slosh baffles would help keep a spin steady and resist efforts to slow it down.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: sghill on 12/06/2018 02:18 pm
Go Quest is drifting south of the Channel according to an update they just gave the Coast Guard Sounds like they are meeting another ship, possibly "Pacific Talon".

"Pacific Talent"

It's a bulk carrier. It is headed to Port Canaveral from Brazil, where it departed on Nov. 21. The captain is on the radio talking about meeting the pilot boat to go into the port.

https://www.marinetraffic.com/en/ais/home/shipid:3935544/zoom:10
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kevinof on 12/06/2018 02:26 pm
It has nothing to do with recovery - just working it's way to the anchorage point to wait for clearance to enter port.

Go Quest is drifting south of the Channel according to an update they just gave the Coast Guard Sounds like they are meeting another ship, possibly "Pacific Talon".

"Pacific Talent"

It's a bulk carrier. It is headed to Port Canaveral from Brazil, where it departed on Nov. 21. I doubt it is going over to the party.

https://www.marinetraffic.com/en/ais/home/shipid:3935544/zoom:10

On the otherhand, it does have several VERY large cranes on its deck...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lee Jay on 12/06/2018 03:00 pm
Musk's tweet was;

Quote
Engines stabilized rocket spin just in time, enabling an intact landing in water! Ships en route to rescue Falcon.

My question is, how can a single engine landing burn (center engine) null a spin? I'm not claiming it didn't (the video makes it clear it did) I'm just trying to understand how a center engine could generate the needed torque. 

This was answered farther back in the thread
Musk is referring to the cold nitrogen thrusters as "engines".
There is protracted debate about when a single, on-axis engine can induce torque to increase or decrease roll rates, but the basic answer is it can't do much, and certainly didn't for this fist stage.

This seems correct to me, save for the fact that the center engine does contribute substantially by slowing the decent and therefore reduces the aerodynamic torque being applied by the wayward grid fins, thus allowing the relatively weak cold gas thrusters to do their jobs.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: flyright on 12/06/2018 03:04 pm
Per marine radio, a diving team is joining Tugboat Eagle and Go Quest.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Pete on 12/06/2018 03:08 pm

Here's my question...If the stage knows it's aborting a pad landing to land on the ocean, why then lower the legs at all?  Would it then make lifting onto a barge eaiser with the legs connected to the stage?
It might allow the legs to take some of the impact instead of the engines taking it all.

It would also make the tip=over speed a good bit slower.

But I'm sure the stage knows nothing about that, it would have a VERY hardcoded and foolproof routine that says "ground detected at distance X, deploy legs" regardless of the nature of the ground, lateral velocity, etc. Point in case, the very failed landing of the FalconHeavy core started to try to deploy legs, despite approaching the sea at several hundred miles per hour.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mlindner on 12/06/2018 03:09 pm
Musk's tweet was;

Quote
Engines stabilized rocket spin just in time, enabling an intact landing in water! Ships en route to rescue Falcon.

My question is, how can a single engine landing burn (center engine) null a spin? I'm not claiming it didn't (the video makes it clear it did) I'm just trying to understand how a center engine could generate the needed torque. 

This was answered farther back in the thread
Musk is referring to the cold nitrogen thrusters as "engines".
There is protracted debate about when a single, on-axis engine can induce torque to increase or decrease roll rates, but the basic answer is it can't do much, and certainly didn't for this fist stage.

This seems correct to me, save for the fact that the center engine does contribute substantially by slowing the decent and therefore reduces the aerodynamic torque being applied by the wayward grid fins, thus allowing the relatively weak cold gas thrusters to do their jobs.

It also slows the spin by removing any spin energy that is transferred into spins about other axes. The rocket does not want to spin along the axis that runs the length of the booster so it will start to turn into a flat spin over time. These other spins the rocket can counteract and remove.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Dappa on 12/06/2018 03:20 pm
Musk's tweet was;

Quote
Engines stabilized rocket spin just in time, enabling an intact landing in water! Ships en route to rescue Falcon.

My question is, how can a single engine landing burn (center engine) null a spin? I'm not claiming it didn't (the video makes it clear it did) I'm just trying to understand how a center engine could generate the needed torque. 

This was answered farther back in the thread
Musk is referring to the cold nitrogen thrusters as "engines".
There is protracted debate about when a single, on-axis engine can induce torque to increase or decrease roll rates, but the basic answer is it can't do much, and certainly didn't for this fist stage.

This seems correct to me, save for the fact that the center engine does contribute substantially by slowing the decent and therefore reduces the aerodynamic torque being applied by the wayward grid fins, thus allowing the relatively weak cold gas thrusters to do their jobs.
Not only that, the grid fins will also have slowed down the rotation. Like a corkscrew, a given vertical speed will have a matching angular velocity where the grid fins slice through the air perfectly. As the vertical speed drops, the rotation will drop too.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RoboGoofers on 12/06/2018 03:40 pm
I think the anti slosh baffles had a lot to do with stopping the spin.

Anti slosh baffles only inhibit accelerations, they don't inhibit velocities, because there is no sloshing going on. In fact anti-slosh baffles would help keep a spin steady and resist efforts to slow it down.

I suppose i should have said "the complex interactions of the friction from the remaining fuel and the tank walls and the internal obstructions such as baffles whilst the engine is firing" play a part in slowing the spin rate.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/06/2018 04:05 pm
Diving seems to be going on now.?.  Go Quest is on scene, Go Navigator is in port, Go Searcher is...hmm, I don't know where.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: AJW on 12/06/2018 04:07 pm
From the 'landing' video, it sure looks like the RCS thrusters are fighting the gridfin induced spin from the moment it starts until the booster hits the water.  It isn't always visible near the base of the booster, especially while the booster is at high speed, but a short plume is visible when in the right light.  Without the RCS system fighting it, the rate of the spin would have continued to increase.  As the landing burn starts, the speed of the booster slows, so the gridfins become less and less effective, allowing the RCS system to counteract the spin until it is nullified just before landing.  I think that releasing the legs may have had some impact but it was negligible compared to the RCS.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/06/2018 04:13 pm
If the engine control system is taking the grid fins into account, then I think even a single engine can do it.


No, it is the grid fins and RCS that provide roll control.  A single engine can not provide roll control.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/06/2018 04:15 pm
I am curious to see how exactly they'll approach bringing a rocket back into port that didn't land on an ASDS. Why not just fish it out, put it on OCISLY, and then take it back to port that way?

And how exactly would you 'just' fish it out?


Put the crane on OCISLY


That is partially serious, but understand stability issues associated with sea state and that OCISLY's deck might not be able to handle the load

There are such things as crane barges...my son worked on one when he was in the Army Reserves (he was a Watercraft Engineer) ... they trained to lift some hairy stuff in non-ideal sea states

not in Port Canaveral
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/06/2018 04:18 pm

This assertion is contradicted by the onboard footage. The roll is mostly nulled by the time the legs begin to deploy.


Nah, the video confirms my point.   It is still spinning at the beginning of leg deployment. The leg deployment stops the roll.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/06/2018 04:20 pm
I don't really agree with that, the instant the legs pop out the roll basically stops.

The tracking shots all show that the vehicle's roll rate visibly decreases well before the legs pop out. The leg deployment helped, but the engine clearly did much, or even most, of the work first.

No, the engine has no role in stopping the roll.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/06/2018 04:21 pm

Here's my question...If the stage knows it's aborting a pad landing to land on the ocean, why then lower the legs at all?  Would it then make lifting onto a barge eaiser with the legs connected to the stage?
It might allow the legs to take some of the impact instead of the engines taking it all.

Great answers:  Thanks CorvusCorax and Nomadd.

Legs have the radar altimeter for landing too.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: groundbound on 12/06/2018 04:23 pm

No, the engine has no role in stopping the roll.

I often miss your humor but I caught that one.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/06/2018 04:24 pm
The engine, as long as it continues to fire, takes out spin at a fixed rate, and doesn't slow down towards the end.

No, the engine can not provide any torque on the longitudinal axis.  It is on the centerline, it can only provide pitch and yaw.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/06/2018 04:30 pm
I think that releasing the legs may have had some impact but it was negligible compared to the RCS.

It isn't "negligible".  The change in the moments of inertia was large and did remove most of the roll.  Just like a skater.  A skater's arms are a small fraction of the mass of the skater but it can greatly slow the spin.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Orbiter on 12/06/2018 04:32 pm
Conservation of angular momentum, guys. Jim's right, the legs stopped the roll. Think about the axis of rotation here in relation to the force of the engine, how could the engine possible stop the roll?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/06/2018 04:38 pm
A neat combination of views of the landing:

https://www.youtube.com/watch?v=_t6Rba1BuIo

Sadly the camera guy for the lower left feed "had one job", and managed to miss the most interesting part of the early wobble. Grumble.  :)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: sfxtd on 12/06/2018 04:40 pm
From the 'landing' video, it sure looks like the RCS thrusters are fighting the gridfin induced spin from the moment it starts until the booster hits the water.  It isn't always visible near the base of the booster, especially while the booster is at high speed, but a short plume is visible when in the right light.  Without the RCS system fighting it, the rate of the spin would have continued to increase.  As the landing burn starts, the speed of the booster slows, so the gridfins become less and less effective, allowing the RCS system to counteract the spin until it is nullified just before landing.  I think that releasing the legs may have had some impact but it was negligible compared to the RCS.

I think this analysis makes the most sense.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/06/2018 04:44 pm
Conservation of angular momentum, guys. Jim's right, the legs stopped the roll. Think about the axis of rotation here in relation to the force of the engine, how could the engine possible stop the roll?
Conservation of angular momentum means that the legs can only diminish the rate of rotation by the ratio of the moments of inertia (before and after).  "Ratio" means that by definition they can't stop the rotation, only reduce it.

The ratio can't be large either. The legs are not that heavy, their initial radius is about 2 m, and when they open up, most of their mass moves only a small distance.  Even with the r2 term, I'd be surprised if the ratio was 2x.

The engine, OTOH, can reduce the rate of rotation to zero, but coupling an axial engine to axial rotation is tricky and only works when there are things like grid fins to help cause precession.  I think the main contribution of the legs was to make the engine much more effective, plus give the obvious one time reduction from their moment of inertia.

-----
ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meberbs on 12/06/2018 04:56 pm
Nah, the video confirms my point.   It is still spinning at the beginning of leg deployment. The leg deployment stops the roll.
Wrong.
Conservation of angular momentum, the stage has just as much angular momentum before and after the leg deploy. It may be spinning slower, but there is just as much momentum to cancel. The only way in which the legs actually helped bring the spinning to a true stop is the additional rotational air drag on them.

No, the engine has no role in stopping the roll.
Wrong.
As has been said in other posts on here, the roll bled into other axes, which seems to be true if you look carefully at the video. Once the spin axis is no longer lined up with the main axis of the booster, the engine has some useful control authority.
Also, of the effects that allowed the booster to stop the roll, one of the most important would be the change in torque due to the grid fins. There are 2 effects, one is that as the booster slows down, the aerodynamic force on the fins decreases, which enables the RCS thrusters to start winning the fight. Second is that for a given downward speed, there should be a preferred spin rate at a stable equilibrium where the grid fins apply no torque. Decreases in the downward air speed reduce that spin rate, causing the grid fins to actually apply some torque in a helpful direction. Your pithy statements which ignore all of this are not helpful.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/06/2018 05:10 pm

Wrong.
As has been said in other posts on here, the roll bled into other axes, which seems to be true if you look carefully at the video. Once the spin axis is no longer lined up with the main axis of the booster, the engine has some useful control authority.

Wrong.  We are not talking spin but roll.  The other axis are not part of the discussion, of course the engine can affect those.

Your pithy statements which ignore all of this are not helpful.

Those are not part of the discussion.  The vehicle was no longer in a flat spin at the point of the discussion.  There only was roll remaining.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/06/2018 05:13 pm
"Ratio" means that by definition they can't stop the rotation, only reduce it.

That is why the term "remove most of the" was used.


The engine, OTOH, can reduce the rate of rotation to zero,

No, it has no affect on rates on the roll axis
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/06/2018 05:19 pm

The engine, OTOH, can reduce the rate of rotation to zero,

No, it has no affect on rates on the roll axis

That's categorically false.  A) See Musk's statement.  B) This is not a classical rigid body in vacuum problem.  The axes of rotation are coupled, as has been pointed above.  C) You can see the rate of rotation (roll) decreasing once the engine turns on, and before leg deployment.

EDIT: clarified this is about roll as well.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/06/2018 05:20 pm
No where in the discussion have I said "spin".  I am only talking about roll and that was only happening near the end when vehicle was vertical.    Of course, the engine damps out pitch and yaw.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/06/2018 05:21 pm
Legs have the radar altimeter for landing too.

Are you sure the radar is not actually mounted on the base of the rocket, I think a white rectangular addition to the side of the base was speculated in (now older) images?

Landing legs deploy mere meters before touchdown, I'd think it would be to late to incorporate radar altimetry into the thrust profile at that point.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/06/2018 05:23 pm
Logan reports to Eagle: Divers are clear, but there are some "guys around the leg on the surface"
Mental image of Slim Pickings riding that bomb...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/06/2018 05:24 pm
As has been said in other posts on here, the roll bled into other axes

Because the grid fins were locked into such a position that they induced a lift vector in addition to a roll torque?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meberbs on 12/06/2018 05:34 pm
Wrong.
As has been said in other posts on here, the roll bled into other axes, which seems to be true if you look carefully at the video. Once the spin axis is no longer lined up with the main axis of the booster, the engine has some useful control authority.
Wrong.  We are not talking spin but roll.  The other axis are not part of the discussion, of course the engine can affect those.
They aren't perfectly separable concepts in the real world, spins are not simply tied to a single body axis except in certain cases of perfect symmetry.

Your pithy statements which ignore all of this are not helpful.
Those are not part of the discussion.  The vehicle was no longer in a flat spin at the point of the discussion.  There only was roll remaining.
The things I described just before the quoted statement apply to the ideal pure roll case. You cannot redefine yourself out of the fact that your statements were incorrect.

"Ratio" means that by definition they can't stop the rotation, only reduce it.
That is why the term "remove most of the" was used.
Again, the moment of inertia change from leg deploy removes none of the angular momentum. The angular velocity may reduce, but the remaining work other mechanisms need to do to stop the spinning is unchanged.

No where in the discussion have I said "spin".  I am only talking about roll and that was only happening near the end when vehicle was vertical.    Of course, the engine damps out pitch and yaw.
If you think there is a difference, then you don't know what you are talking about. Unless there is perfect symmetry, a pure roll will turn into a generic spin which can then be removed.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vanoord on 12/06/2018 05:59 pm
As has been said in other posts on here, the roll bled into other axes

Because the grid fins were locked into such a position that they induced a lift vector in addition to a roll torque?

Presumably, if the grid fins were locked into different orientations that would induce sufficient instability to turn the roll into a wobble.

Going back to the point about the legs reducing the roll - yes, they had a marked effect but the roll was very much reduced by that time compared to the peak.

If anyone doesn't believe that, go the the onboard view uploaded by Elon and count each revolution, preferably out loud (the reflection of the sun on the sea is an obvious marker).

My guess would be that as the speed of the stage decreased, the effect of the stuck grid fins reduced and allowed the gas thrusters to start to get control.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/06/2018 05:59 pm
Excuse me while I put a momentary break into the "I know physics better than you **** measuring" with this...

From the update thread:

heard:  There is nowhere to put his feet to pull it up on the other side.

I wish I could suggest them to throw a rope over the top or something.

We're not there. Let's assume that they know what they are doing, and are being instructed by SpaceX who certainly know the booster and how to handle it.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: DigitalMan on 12/06/2018 06:03 pm
Excuse me while I put a momentary break into the "I know physics better than you **** measuring" with this...

From the update thread:

heard:  There is nowhere to put his feet to pull it up on the other side.

I wish I could suggest them to throw a rope over the top or something.

We're not there. Let's assume that they know what they are doing, and are being instructed by SpaceX who certainly know the booster and how to handle it.

relax, it was a joke.  clearly I need a new one.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Chris Bergin on 12/06/2018 06:13 pm
Ok, calm it down, everyone. This is not the party thread, nor is it the party pooper thread.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: HVM on 12/06/2018 06:19 pm
Landing burn slows down the airflow over (through) the grid fins, and fin's sides start to works as speed brakes, for the roll induced airflow. The landing leg deployment is not only change moment of inertia*, legs work as speed brakes too and reduce roll rate.

*moment of inertia and rotational speed changes, angular momentum remains constant. -elementary school physics.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/06/2018 07:04 pm
Its fun to see you argue over nothing. You are both right, yet fail to see that the other is right too.
1. The stage was rotating with high roll rate but also significant precession, especially early in the descent as the fins induced both a rolling and a pitching force.
2. The stage was fighting both roll and pitch/yaw with cold gas thrusters.
3. As the air density increased the roll rate did too, reducing prevession. In thos phase the booater is effectively spin stabilized.
4. Once the stage was subsonic the roll rate decreased as airspeed decreased.
5. The precession increased too, leading to quite an extreme lean during powered flight.
6. At the beginning of powered flight, main engine was almost in line with rotation axis, no authority over roll rate, effect of cold gas thrusters only.
7. With the "lean" seconds before touchdown, rotation axis was not inline and main engine could decrease rotation rate using yaw gimbal.
8. the booster uprights itself, but the rotation rate is now greatly reduced. Engine is now again in line with rot axis but booster is too slow for grid fins to do much harm. Gas thrusters still figgt rotation.
9. Throwing the legs out has a very visinle "ballerina" effect and instantly reduces rotation rate to a fraction of the already slowed rate.
10. Legs hit the water, arresting the remaining rotation. Booster seems to undergo some twisting oscillation where the interstage with grid fins overshoots by a few degrees, then twists back.
11. Booster goes horizontal and splashed down.


Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: edzieba on 12/06/2018 07:14 pm
Theory:

The hydraulic pump failure happened extremely early in descent (not long after - if not during - grid-fin deployment).

Evidence:

- The grid-fins do not move at all after deployment until after the roll has started, at which point one of the two visible grid fins 'flops' over to the end of travel and remains there.

- RCS thruster pulses are visible after atmospheric entry, something I can't recall seeing before. Likely the stage attempting to use whatever control authority it has available to it.

- Stage does not perform normal 'side on' descent to gain free aerobraking using the grid-fins (fins 'kick out; the top of the stage to the side against airflow, giving it a larger cross-section so more drag), so would be descending faster than normal

- Flight Club's CRS-16 sim has a nominal descent going transonic at T+460 (7 m 40s). The grid fin 'flops' over at 7m25s, which could match up with a faster than normal descent.

- The known 'transonic control inversion' issue with grid-fins would explain why at that time the stage rotation changes direction dramatically: while supersonic the free-floating grid fins were oriented slightly off and imparting a small clockwise roll moment. As the stage goes transonic, the grid-fin briefly acts as a big flap tangential to the airflow rather than a fin parallel to it, imparting a large momentary force to the fin that flops it over in the opposite direction. As the stage slows further, the grid fin then returns to acting as a fin again, and is now applying a grater roll moment in the opposite (anticlockwise) direction. We see this in the on-board video: clockwise roll slowly increasing in rate, grid fin flops over, roll stops, roll direction reverses with dramatic increase in roll rate.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: haywoodfloyd on 12/06/2018 07:26 pm
Logan reports to Eagle: Divers are clear, but there are some "guys around the leg on the surface"
Mental image of Slim Pickings riding that bomb...


I think you meant Slim Pickens.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Okie_Steve on 12/06/2018 07:29 pm
I apparently misunderstood Chris B's request to keep the spin discussion L2, because my question got deleted, so I'll ask it here instead.

The last time they had a floating stage recovery was discussed but eventually it was scuttled because IIRC there was no way to vent and it was too dangerous. So, is there any information about what changes were made to make it more feasible to try this time?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/06/2018 07:34 pm
Logan reports to Eagle: Divers are clear, but there are some "guys around the leg on the surface"
Mental image of Slim Pickings riding that bomb...


I think you meant Slim Pickens.
Heh yes ...

-----
ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: pb2000 on 12/06/2018 07:36 pm
I apparently misunderstood Chris B's request to keep the spin discussion L2, because my question got deleted, so I'll ask it here instead.

The last time they had a floating stage recovery was discussed but eventually it was scuttled because IIRC there was no way to vent and it was too dangerous. So, is there any information about what changes were made to make it more feasible to try this time?
The flight computer on the booster continued transmitting after touchdown+tip and reported that the safeing procedure was completed. Also, they want this one back, but 1032.2 was always meant to be expended.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/06/2018 07:40 pm
I apparently misunderstood Chris B's request to keep the spin discussion L2, because my question got deleted, so I'll ask it here instead.

The last time they had a floating stage recovery was discussed but eventually it was scuttled because IIRC there was no way to vent and it was too dangerous. So, is there any information about what changes were made to make it more feasible to try this time?

The stage was still transmitting data after splashdown, so they were able to confirm it had gone through its safing procedures, including venting fuel and LOX.

*edit* NINJA'D
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: edkyle99 on 12/06/2018 07:41 pm
I apparently misunderstood Chris B's request to keep the spin discussion L2, because my question got deleted, so I'll ask it here instead.

The last time they had a floating stage recovery was discussed but eventually it was scuttled because IIRC there was no way to vent and it was too dangerous. So, is there any information about what changes were made to make it more feasible to try this time?
In my view, SpaceX has not made any appreciable changes to account for a water "landing".  This is simply not the intended mode of recovery.  The last one sank due to wave action.  This one is likely also being stressed by wave action, albeit smaller waves, and won't last forever on the surface, not to mention the lengthy salt water exposure.  I don't see how this stage could ever be reused.  If the company wants to make adjustments for this scenario, it should design an easier way to sink the floating stage.

 - Ed Kyle 
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: rakaydos on 12/06/2018 07:41 pm
I apparently misunderstood Chris B's request to keep the spin discussion L2, because my question got deleted, so I'll ask it here instead.

The last time they had a floating stage recovery was discussed but eventually it was scuttled because IIRC there was no way to vent and it was too dangerous. So, is there any information about what changes were made to make it more feasible to try this time?
it was probably a failure of imagination last time around. The stage was supposed to come to 0 velocity just above the water, then shut down, crash and blow up. They missed the target in the EXACT way needed to splash down without blowing up, something the designers never considered.

Now, of course, they know it's possible, and probably even aim for a safe water landing at least for RTLS. Auto-safing is just common sense now that we know it's possible.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: StuffOfInterest on 12/06/2018 07:45 pm
Just saw on the update thread that GO Quest has recovered a leg.  I guess they are detaching the legs in the water.  Has to be some tricky work, but I guess if they do it will at least make it possible to tow the stage in and/or lift it out of the water.

https://twitter.com/spacexfleet/status/1070777385946103809

Quote
GO Quest has confirmed to the coast guard over marine radio that they recovered a rocket leg earlier today.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/06/2018 07:51 pm
Just saw on the update thread that GO Quest has recovered a leg.  I guess they are detaching the legs in the water.  Has to be some tricky work, but I guess if they do it will at least make it possible to tow the stage in and/or lift it out of the water.

https://twitter.com/spacexfleet/status/1070777385946103809

Quote
GO Quest has confirmed to the coast guard over marine radio that they recovered a rocket leg earlier today.

It's the new procedure..  detach the one that's underwater, then the stage auto-rotates to submerge the next one, repeat x4...

Either that, or one leg was lost during the topple maneuver...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: dnavas on 12/06/2018 07:52 pm
Just saw on the update thread that GO Quest has recovered "a leg".  I guess they are detaching the legs in the water.  Has to be some tricky work, but I guess if they do it will at least make it possible to tow the stage in and/or lift it out of the water.

If the stage was in trouble, I would have thought that the titanium fins would be higher priority, so I'm going to assume the plan continues to be full recovery of the stage (though, let's face it, *reuse* seems thoroughly unlikely).
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: joncz on 12/06/2018 07:52 pm
Quote
Just saw on the update thread that GO Quest has recovered a leg.  I guess they are detaching the legs in the water.  Has to be some tricky work, but I guess if they do it will at least make it possible to tow the stage in and/or lift it out of the water.


I don't believe that's the case.  Coast Guard asked them if the piece they recovered was from the interstage.  They said it was from the leg, and CG asked them to confirm that was the only piece recovered.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ellindsey on 12/06/2018 07:53 pm
I think it's a bit optimistic to assume the leg was removed intentionally.  I suspect it was broken off either by wave action or accidentally by hitting a tugboat or tow rope.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/06/2018 08:13 pm
https://twitter.com/KillianPhoto/status/1070781952398118912

Note - some (on the UPDATE thread) are interpreting the first image as showing a gash/hole in the interstage. But what looks like  a hole is actually an gray inflated bag attached to the grid fin. The bag has weird shadows thrown on it from the grid fin, making it look like water.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: saliva_sweet on 12/06/2018 08:21 pm
The fin is there. There is a gash, the wall is bent. There is no bag attached to the fin.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/06/2018 08:23 pm
The fin is there. There is a gash, the wall is bent. There is no bag attached to the fin.

What gash? Where is it bent? Look closer.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: stcks on 12/06/2018 08:25 pm
The fin is there. There is a gash, the wall is bent. There is no bag attached to the fin.

What gash? Where is it bent? Look closer.

Interstage
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/06/2018 08:25 pm
The fin is there. There is a gash, the wall is bent. There is no bag attached to the fin.

What gash? Where is it bent? Look closer.

I remember comments after Orbcomm-OG2 landing that the tankage had to be bent and crumpled. Turned out it was just a soot pattern, but hey. This is almost as interesting to follow.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/06/2018 08:27 pm
The fin is there. There is a gash, the wall is bent. There is no bag attached to the fin.

What gash? Where is it bent? Look closer.

Interstage

Sigh. I can't wait to see this thing lifted out of the water so people will see what is actually there. But then I remember all the old discussions where people insisted certain dirt streaks on the recovered booster was showing buckles in the tank. They never admitted they were wrong.

Anyway, look at BOTH images I attached a few posts ago. The gash mush come and go. It is a flotation bag with grid fin shadows on it.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ellindsey on 12/06/2018 08:29 pm
Zooming in on the first picture, you can see that not only is there a large rip in the interstage, but the shadow pattern shows a bend in the interstage wall where nearly a quarter of the interstage circumference has been torn and bent slightly outwards.  The top of the interstage is no longer circular, but has an outward bend in the torn area.  This is also slightly visible in the image which shows the top of the interstage, although there the torn section is mostly submerged.  This is going to make it impossible to attach the lifting cap, even assuming they could with the rocket sideways.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/06/2018 08:29 pm
If you zoom in on the full res images its quite clear. But the stage is rotated ( roll axis ) 90 degrees betwern the two photos showing stage from top and side.

In the too view where u can see inside the interstage the broken section is at the bottom, extending into the water.

In the side view the broken section is above the warer toeards tge viewer.

All 4 grid fins are there
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/06/2018 08:31 pm
If you zoom in on the full res images its quite clear. But the stage is rotated ( roll axis ) 90 degrees betwern the two photos showing stage from top and side.

In the too view where u can see inside the interstage the broken section is at the bottom, extending into the water.

In the side view the broken section is above the warer toeards tge viewer.

All 4 grid fins are there

The stage has not rotated in the two pictures. The SpaceX / F9 logo and US flag are on top of the stage in both pictures.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/06/2018 08:32 pm
If you zoom in on the full res images its quite clear. But the stage is rotated ( roll axis ) 90 degrees betwern the two photos showing stage from top and side.

In the too view where u can see inside the interstage the broken section is at the bottom, extending into the water.

In the side view the broken section is above the warer toeards tge viewer.

All 4 grid fins are there

The stage is not rotated 90 degrees. Pay attention to the where SpaceX and F9 logos are. :) And note that the interstage has THREE outer separation pushers at 120 degrees apart. If it was rotated 90 degrees they would not line up the same way.

I so look forward to seeing this on land.  ;D (stcks, ellindsey, CorvusCorax, saliva_sweet)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vanoord on 12/06/2018 08:33 pm
I think it's a bit optimistic to assume the leg was removed intentionally.  I suspect it was broken off either by wave action or accidentally by hitting a tugboat or tow rope.

If one of the legs had broken off, one would expect the stage to have rolled round so the lost leg was upwards.

If one leg has been removed *intentionally* to reduce the draught then that would explain the buoyancy bags, ie put them on the two horizontal legs, then drop the underwater leg off.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: stcks on 12/06/2018 08:36 pm
I so look forward to seeing this on land.  ;D

What will you do when you see a real gash there 8) Tell you what, ... loser pays for a 6-month L2 membership for someone?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/06/2018 08:48 pm
Given that we can already see that there isn't a gash, this is a very poor wager.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: 1 on 12/06/2018 08:51 pm
Wondering what kind of discussions might be going on right now for future "wet" recoveries. Can we take a page from the shuttle SRB experience?

Hypothetical. Let's say next time that a tanker gets sent out to flood the RP-1 tank with deionized water. The stage rights itself, and sinks much (most?) of the way below water. Stresses due to wave action should be reduced, and workers on the surface might have a much easier time fixing the end cap to allow crane lift right from the drink and back onto OCISLY avoiding the issue of towing altogether.

Feasible? Or am I talking about my butt more than I already realize? I'm fully aware that those people out there, with their 24 hours of experience, are now the worlds foremost experts on towing a floating rocket stage that was never intended to be towed or floated.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/06/2018 09:00 pm
Wondering what kind of discussions might be going on right now for future "wet" recoveries.

The "discussions" are probably like : "let's avoid them, m'kay?"
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vanoord on 12/06/2018 09:01 pm
IMHO, a lot is going to depend on how much they learn from this one / how much can be recovered.

I'd guess the aim will be to analyse this core to see what's been stressed the most, figure out the pump failure, *possibly* try and recover an engine to see if can be re-started and recover the grid fins and legs.

In future, I'd expect grid fin and leg recovery and not a lot else.

With the amount of out-of-parameter stress this stage has ensured, it's a useful learning exercise - but I don't see one stage ditched for every 20-30 recovered being anything than a parts scavenging exercise.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/06/2018 09:01 pm
Given that we can already see that there isn't a gash, this is a very poor wager.

This is pretty amazing. Do you see the dress as white and gold?

Looking down the barrel of the interstage there is CLEARLY no enormous gash on the side of it in the same place where there is that distorted reflection in the previous picture.

We've already established that the booster is in the same orientation in both pictures.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/06/2018 09:01 pm
Given that we can already see that there isn't a gash, this is a very poor wager.

This is pretty amazing. Do you see the dress as white and gold?

Are you suggesting that the gash will appear and disappear depending on light conditions?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: flyright on 12/06/2018 09:03 pm
Carnival Liberty is outbound and will likely be passing a mile or two from the booster recovery operation. Maybe there will be some fans on board with good lenses.  :)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: saliva_sweet on 12/06/2018 09:11 pm

Looking down the barrel of the interstage there is CLEARLY no enormous gash on the side of it in the same place where there is that distorted reflection in the previous picture.

We've already established that the booster is in the same orientation in both pictures.

The booster is unquestionably in the same orientation.

Are you suggesting that the gash will appear and disappear depending on light conditions?

I think it's another mystery of human perception. I am absolutely certain there is a large gash. Probably the broken flap is moving with waves so it's less visible from the top view. But deformation of the left side is visible from that view as well as the border of the gash on the bottom.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/06/2018 09:25 pm
Great tracking video of the landing - and this shot catches the severe tumble a few seconds after the braking burn.  :o

https://www.youtube.com/watch?v=WsyfC2i0mmQ
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/06/2018 09:26 pm

Looking down the barrel of the interstage there is CLEARLY no enormous gash on the side of it in the same place where there is that distorted reflection in the previous picture.

We've already established that the booster is in the same orientation in both pictures.

The booster is unquestionably in the same orientation.

Are you suggesting that the gash will appear and disappear depending on light conditions?

I think it's another mystery of human perception. I am absolutely certain there is a large gash. Probably the broken flap is moving with waves so it's less visible from the top view. But deformation of the left side is visible from that view as well as the border of the gash on the bottom.

Where's the "flap" in the 1st picture?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/06/2018 09:30 pm
 
Great tracking video of the landing - and this shot catches the severe tumble a few seconds after the braking burn.  :o

Wow. Good to see they transitioned from filming a camera screen with a camera to a proper capture in the last couple of launches.

If you pause at around 1:03 you can actually see the bow shock refracting the light of background clouds  :o

Reminds me of WB-57 chase plane footage of IIRC STS-114 launch, but the public video quality was very bad and the video was interlaced and created horrendous artifacts.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/06/2018 09:36 pm
Wow. Good to see they transitioned from filming a camera screen with a camera to a proper capture in the last couple of launches.

If you pause at around 1:03 you can actually see the bow shock refracting the light of background clouds  :o

Here is an animated GIF of the most eye-popping sequence  :o (not sped up!)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/06/2018 09:47 pm
Here is an animated GIF of the most eye-popping sequence  :o (not sped up!)

I think that's the point we got to see in the live stream, that roll reversal before they cut the feed. These guys have a serious tracking setup.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Gliderflyer on 12/06/2018 09:54 pm
Put me in the interstage is broken camp. The lower left section doesn't line up with the rest of it.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/06/2018 09:54 pm
Wow. Good to see they transitioned from filming a camera screen with a camera to a proper capture in the last couple of launches.

If you pause at around 1:03 you can actually see the bow shock refracting the light of background clouds  :o

Here is an animated GIF of the most eye-popping sequence  :o (not sped up!)

I can hear the "Oh! ... ... wooooOOOAAAHHH!!" from the SpaceX cafeteria crowd in my head as I watch that lol xD
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ellindsey on 12/06/2018 09:59 pm
Two very quick drawings where I outlined the damage to the interstage.  The first shows the location of the gash and a bend where the separated section of the interstage is pulled outward from its normal position.  The second is the end-on shot, where you can see that the top of the interstage is no longer circular, and has a large opening facing downwards.  Yellow shows the new profile of the top of the interstage, red is the edges of the tear and the position of the bend in the first image.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: flyright on 12/06/2018 10:05 pm
This might explain why the Coast Guard was asking Go Quest if they had picked up a piece of the interstage. Go Quest replied that they picked up a piece of a leg.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/06/2018 10:11 pm
Put me in the interstage is broken camp. The lower left section doesn't line up with the rest of it.

That'll buff right out.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/06/2018 10:17 pm
Two very quick drawings where I outlined the damage to the interstage.  The first shows the location of the gash and a bend where the separated section of the interstage is pulled outward from its normal position.  The second is the end-on shot, where you can see that the top of the interstage is no longer circular, and has a large opening facing downwards.  Yellow shows the new profile of the top of the interstage, red is the edges of the tear and the position of the bend in the first image.

Hmm, you could be on to something. There is new video in the update thread, it seems to support this too.  (although only 360p res uploaded so far)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/06/2018 10:18 pm
Two very quick drawings where I outlined the damage to the interstage.  The first shows the location of the gash and a bend where the separated section of the interstage is pulled outward from its normal position.  The second is the end-on shot, where you can see that the top of the interstage is no longer circular, and has a large opening facing downwards.  Yellow shows the new profile of the top of the interstage, red is the edges of the tear and the position of the bend in the first image.

That "large opening facing downwards" is just water inside the interstage.

I'm still not seeing a gash on the side of the interstage, I think it's just light bouncing off the water onto the interstage.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: llanitedave on 12/06/2018 10:18 pm
Also, there are no floatation bags on the interstage, so what looks like water, pretty much has to be water.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/06/2018 10:19 pm
Hmm, you could be on to something. There is new video in the update thread, it seems to support this too.  (although only 360p res uploaded so far)

Yeah, seems to me youtube is taking its sweet time encoding the other quality options.

Once it's done it should be legen-wait for it-dary.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: MattBaker on 12/06/2018 10:19 pm
Regardless of any gashes and landing legs being intentionally removed or torn off by Aquaman himself (clearly this whole thing is paid promotion from DC Comics proving water > space):

The stage has been in salt water for nearly 30 hours already and even if it would be out by 9 AM sharp tomorrow morning, 44 hours. Then hydraulics already failed before landing, who knows what caused that, and the whole thing took a sizeable whack when it tipped over into water and spent however many hours it will ultimately be subjected to the constant forces of ocean waves jerking it around, which might or might not have torn any gashes into it.

Add the recovery to it, it's not something that's really been done before so they might as well further damage it even with the best intentions.

All that taken together: Do you think this stage will ever fly again?

The way I see it, even if they successfully recover it, which seems like quite a headache, all value this stage has is forensics, which might be valuable in itself though.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Kabloona on 12/06/2018 10:22 pm

Here is an animated GIF of the most eye-popping sequence  :o (not sped up!)

Eye-popping indeed. Apollo 13, you're heading for gimbal lock!
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: leetdan on 12/06/2018 10:32 pm
Delta Mariner is heading in to port, and will pass right by the recovery area.  It's a shame they won't be passing during daylight hours, the photo caption possibilities would be nearly endless!
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/06/2018 10:35 pm
Two very quick drawings where I outlined the damage to the interstage.  The first shows the location of the gash and a bend where the separated section of the interstage is pulled outward from its normal position.  The second is the end-on shot, where you can see that the top of the interstage is no longer circular, and has a large opening facing downwards.  Yellow shows the new profile of the top of the interstage, red is the edges of the tear and the position of the bend in the first image.

You know what? I retract my previous statements. I see the flap now. That illustration was very helpful.

Sorry Lars-J, I'm in the "the interstage is busted" camp.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: DigitalMan on 12/06/2018 10:51 pm
Two very quick drawings where I outlined the damage to the interstage.  The first shows the location of the gash and a bend where the separated section of the interstage is pulled outward from its normal position.  The second is the end-on shot, where you can see that the top of the interstage is no longer circular, and has a large opening facing downwards.  Yellow shows the new profile of the top of the interstage, red is the edges of the tear and the position of the bend in the first image.

You know what? I retract my previous statements. I see the flap now. That illustration was very helpful.

Sorry Lars-J, I'm in the "the interstage is busted" camp.

It seems to me the interstage would have impacted the ocean with the most force since it is at the top.  Also interesting that the damage is on the same side as the probable leg 'issue'.  Whether the leg was damaged or removed is a good question but I don't recall hearing anything about leg removal on the radio link.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/06/2018 10:52 pm
AmericaSpace has an article with pictures looking down the barrel that clearly shows the interstage is broken.

https://www.americaspace.com/2018/12/06/teams-working-to-recover-floating-falcon-9-rocket-off-cape-canaveral/
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/06/2018 11:09 pm
Two very quick drawings where I outlined the damage to the interstage.  The first shows the location of the gash and a bend where the separated section of the interstage is pulled outward from its normal position.  The second is the end-on shot, where you can see that the top of the interstage is no longer circular, and has a large opening facing downwards.  Yellow shows the new profile of the top of the interstage, red is the edges of the tear and the position of the bend in the first image.

You know what? I retract my previous statements. I see the flap now. That illustration was very helpful.

Sorry Lars-J, I'm in the "the interstage is busted" camp.

Yep, I see it too. I stand corrected. Fortunately my hat is very tasty.  ;D
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: flyright on 12/06/2018 11:16 pm
SpaceX is moving the ASDS and the little spacer barge about 300 feet to the west.
Getting help from two tugs.

I'm guessing they are making room for the booster.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mlindner on 12/06/2018 11:22 pm
Conservation of angular momentum, guys. Jim's right, the legs stopped the roll. Think about the axis of rotation here in relation to the force of the engine, how could the engine possible stop the roll?

There is not a single axis of rotation, as I've stated several times. The engine helps to null those other axis of rotations. The rocket is also constantly transferring energy into those axes of rotation.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Herb Schaltegger on 12/06/2018 11:23 pm
Yep, I see it too. I stand corrected. Fortunately my hat is very tasty.  ;D

Good on you.

(Others - too many  should take finding out they're wrong with as much grace and good humor).
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: stcks on 12/06/2018 11:25 pm
Yep, I see it too. I stand corrected. Fortunately my hat is very tasty.  ;D

 ;D I only wish you had taken me up on my wager  :P
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Joffan on 12/06/2018 11:40 pm
I'm not saying that the interstage could be regarded as a LEGO element, but it's probably a close approach to one, in terms of plugging in a replacement. How much of a stage needs to refly before it's a reflight?

Getting into Grandfather's axe/Ship of Theseus territory...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: envy887 on 12/06/2018 11:56 pm
I'm not saying that the interstage could be regarded as a LEGO element, but it's probably a close approach to one, in terms of plugging in a replacement. How much of a stage needs to refly before it's a reflight?

Getting into Grandfather's axe/Ship of Theseus territory...

Just the tail number...

But I can't see them taking apart the tanks, which are welded together. If the tanks fly again, it's a reflight.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/07/2018 12:41 am
I'm not saying that the interstage could be regarded as a LEGO element, but it's probably a close approach to one, in terms of plugging in a replacement. How much of a stage needs to refly before it's a reflight?

Getting into Grandfather's axe/Ship of Theseus territory...

Just the tail number...

But I can't see them taking apart the tanks, which are welded together. If the tanks fly again, it's a reflight.

The longer it sits in the ocean, the less likely it is that it (the major structure) will fly again. But... They can recover the Titanium grid fins now, and that will save some $$$.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Chris_Pi on 12/07/2018 01:10 am
I'm not saying that the interstage could be regarded as a LEGO element, but it's probably a close approach to one, in terms of plugging in a replacement. How much of a stage needs to refly before it's a reflight?

Getting into Grandfather's axe/Ship of Theseus territory...

Rivet the existing serial number plate onto a new thrust structure and call it good...  :)

Definitely looks like the interstage is toast. All the broken-up stuff is well above the gridfin attachment, So that's probably still there along with the misbehaving hydraulic pump.

What I'm wondering is did the top ring on the O2 tank it bolts on to deform any? If it's not round the tank's probably scrap, and that could be it for the rocket regardless of saltwater damage. But The interstage might be quite weak in side-loads like those that probably happened when it slapped the surface. So the tank could be fine.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: DigitalMan on 12/07/2018 01:17 am
Discussions with GoQuest and I don't know who:   A couple guys talking about the plan to come back and be prepared around 6 - 6:30am, but one of them says it could wind up being 11am before they get to attempt bringing it in based on morning traffic.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lee Jay on 12/07/2018 01:36 am
It seems to me the interstage would have impacted the ocean with the most force since it is at the top.

Wouldn't the interstage also suffer the most damage from the slap into the water because it's not pressurized, and the tanks are?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lee Jay on 12/07/2018 01:40 am
This seems correct to me, save for the fact that the center engine does contribute substantially by slowing the decent and therefore reduces the aerodynamic torque being applied by the wayward grid fins, thus allowing the relatively weak cold gas thrusters to do their jobs.

It also slows the spin by removing any spin energy that is transferred into spins about other axes. The rocket does not want to spin along the axis that runs the length of the booster so it will start to turn into a flat spin over time. These other spins the rocket can counteract and remove.

In case anyone doubts the above, I just want to remind everyone of this coolest-of-all demos of the intermediate axis theorem:

https://www.youtube.com/watch?v=1n-HMSCDYtM
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: spacenut on 12/07/2018 02:49 am
Is the Dragon capsule ok and when will it berth with the ISS? 
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ellindsey on 12/07/2018 02:54 am
Is the Dragon capsule ok and when will it berth with the ISS?
What, that boring cargo shipment of moldy mouse food?  Nobody cares about that, all the drama is about the booster landing.

Yeah, it's doing fine.  Solar panels deployed and everything.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: MattBaker on 12/07/2018 03:51 am
NASA TV coverage is on Saturday from 04:30 AM ET for the rendevous and capture scheduled for ~6 Eastern and 7:30 AM ET for the berthing. +5 for UTC and London, +6 for Paris, Berlin, Rome, -3 for the West Coast if you feel like getting up at 1 AM to watch a spacecraft edge ever so slightly closer for one and a half hours.

-Someone who keeps a notepad file of space stuff going on in the next week so he can plan early to get up at 1 AM and watch a spacecraft edge ever so slightly closer for one and a half hours
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/07/2018 04:00 am
Is the Dragon capsule ok and when will it berth with the ISS?

Yea, but its more interesting to watch the sea dragon.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/07/2018 04:10 am
Hypothetical. Let's say next time that a tanker gets sent out to flood the RP-1 tank with deionized water. The stage rights itself, and sinks much (most?) of the way below water. Stresses due to wave action should be reduced, and workers on the surface might have a much easier time fixing the end cap to allow crane lift right from the drink and back onto OCISLY avoiding the issue of towing altogether.

Feasible? Or am I talking about my butt more than I already realize? I'm fully aware that those people out there, with their 24 hours of experience, are now the worlds foremost experts on towing a floating rocket stage that was never intended to be towed or floated.

Or how about this - Put RP-1 in the RP-1 tank.  The stage rights itself and sinks much (most?) of the way below the water.  Broken hydraulic pump is now at the top out of the water, fix it. Then put in Lox, helium, TEA/B, Nitrogen.  Light a fire at the bottom of it and send it back to LZ-1.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Roy_H on 12/07/2018 05:13 am
https://www.youtube.com/watch?v=kSjfBmkl5-I

So, this shows the rocket under tow. Looks like north instead of south?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/07/2018 05:58 am
So, this shows the rocket under tow. Looks like north instead of south?

At that point I believe it was just anchored in place. What looks like movement is likely the current heading south.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kevinof on 12/07/2018 06:37 am
Far as I know the current there is northbound. Either way I think it's just being held in place and not actively towing.

So, this shows the rocket under tow. Looks like north instead of south?

At that point I believe it was just anchored in place. What looks like movement is likely the current heading south.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: woods170 on 12/07/2018 06:38 am
So, this shows the rocket under tow. Looks like north instead of south?

At that point I believe it was just anchored in place. What looks like movement is likely the current heading south.

Correct. At the time that footage was shot the booster was anchored in place. It was not being towed.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/07/2018 06:43 am
So, this shows the rocket under tow. Looks like north instead of south?

At that point I believe it was just anchored in place. What looks like movement is likely the current heading south.
Far as I know the current there is northbound. Either way I think it's just being held in place and not actively towing.

No, it landed off-shore the landing pad, and drifted south towards Port Canaveral where it was at that point.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kevinof on 12/07/2018 06:47 am
Current is going north at 0.7, wind was going south at 10 kts. Wind caused it to drift south.

So, this shows the rocket under tow. Looks like north instead of south?

At that point I believe it was just anchored in place. What looks like movement is likely the current heading south.
Far as I know the current there is northbound. Either way I think it's just being held in place and not actively towing.

No, it landed off-shore the landing pad, and drifted south towards Port Canaveral where it was at that point.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vanoord on 12/07/2018 08:32 am
Wind will probably have more effect on the booster than tide.

Given the damage to the interstage, lifting it out of the water conventionally with a cap would appear to be a no-go.

It should be relatively simple to connect up the large crane to the octaweb to lift most of the weight, but unless they're happy to lift the booster upside down and further damage it when it's put down, presumably a second crane will be required with the booster slung either just under the interstage or at the interbank bulkhead.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Hauerg on 12/07/2018 08:57 am
Regardless of any gashes and landing legs being intentionally removed or torn off by Aquaman himself (clearly this whole thing is paid promotion from DC Comics proving water > space):

The stage has been in salt water for nearly 30 hours already and even if it would be out by 9 AM sharp tomorrow morning, 44 hours. Then hydraulics already failed before landing, who knows what caused that, and the whole thing took a sizeable whack when it tipped over into water and spent however many hours it will ultimately be subjected to the constant forces of ocean waves jerking it around, which might or might not have torn any gashes into it.

Add the recovery to it, it's not something that's really been done before so they might as well further damage it even with the best intentions.

All that taken together: Do you think this stage will ever fly again?

The way I see it, even if they successfully recover it, which seems like quite a headache, all value this stage has is forensics, which might be valuable in itself though.
At least some of the grid fins will fly again. (They are expensive as hell.)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vanoord on 12/07/2018 09:08 am
At least some of the grid fins will fly again. (They are expensive as hell.)

This recovery effort is worth it just to get the fins back.

As for the rest of it, the damage caused by immersion in sea water can be massively reduced by action taken immediately after recovery - for something like a boat engine, that means strip down, wash down and coat in oil as soon as practically possible. If things are left, even for a couple of days, that's usually enough to finish them off.

Anything electrical will be a write-off straight away. For example, water gets down the inside of wires and that's made worse if there's any current in it when it's immersed: even though wires might look okay, they can fail 6, 12, 18 months later. Not the end of the world if it's a little outboard motor on a boat, but a big problem if it's part of a rocket.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: speedevil on 12/07/2018 10:45 am
Anything electrical will be a write-off straight away. For example, water gets down the inside of wires and that's made worse if there's any current in it when it's immersed: even though wires might look okay, they can fail 6, 12, 18 months later. Not the end of the world if it's a little outboard motor on a boat, but a big problem if it's part of a rocket.
I would not be surprised to see a nontrivial fraction of the electronics in well sealed boxes, for the purposes nominally of remaining at near STP during flight, and secondary purposes of avoiding sea air ingress in nominal launch and landing.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/07/2018 10:51 am
At least some of the grid fins will fly again. (They are expensive as hell.)

This recovery effort is worth it just to get the fins back.

And the hydraulic pump for a teardown to see why it stalled, unless salt water ingress has washed away (no pun intended) that evidence by now.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: JoostNL on 12/07/2018 11:20 am
So is there a thread following the berthing operations for Dragon? IIRC there was always a thread for this but I cannot seem to find it.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: sghill on 12/07/2018 01:32 pm
Eagle captain is talking to SpaceX on the radio.

The plan is to bring it into the west basin, then turn it around with two boats.

The webcam-that-shall-not-be-named has a lovely view of the entrance to the port this morning.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: rakaydos on 12/07/2018 01:44 pm
So is there a thread following the berthing operations for Dragon? IIRC there was always a thread for this but I cannot seem to find it.
it's also this thread, but with a long phasing orbit, there's nothing to talk about (yet) on dragon, and lots to talk about on Falcon.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kevinof on 12/07/2018 01:51 pm
Now if only I could remember the name of that webcam that shall  not be named....

Eagle captain is talking to SpaceX on the radio.

The plan is to bring it into the west basin, then turn it around with two boats.

The webcam-that-shall-not-be-named has a lovely view of the entrance to the port this morning.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/07/2018 01:53 pm
Looks like a stiff breeze from the north...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Wolfram66 on 12/07/2018 01:58 pm
Not sure why this is such a difficult problem to solve. SpaceX owns a MARMAC barge, this is designed to do things like this.. Drive lift crane onto OCISLY, dispatch to booster w/ tug, Lift booster on to deck, return to dock, drive crane off OCISLY, deal with booster.....

It's like watching mimes in a box... guys... there IS no box.

There is a similar barge with a crane or excavator currently maintaining the Port Canaveral channel as we speak.... so don't say it can't be done. 

After the last time they soft landed a booster in the water, they should have had a contingency plan in place.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jpo234 on 12/07/2018 01:59 pm
Now if only I could remember the name of that webcam that shall  not be named....

Eagle captain is talking to SpaceX on the radio.

The plan is to bring it into the west basin, then turn it around with two boats.

The webcam-that-shall-not-be-named has a lovely view of the entrance to the port this morning.

Google is your friend. Search for "port canaveral web cam".
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: sanman on 12/07/2018 02:01 pm
Why can't they make gridfins electromechanical instead of hydraulic? Wouldn't that improve their reliability?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/07/2018 02:10 pm
https://www.broadcastify.com/listen/feed/21054
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: edkyle99 on 12/07/2018 02:13 pm
After the last time they soft landed a booster in the water, they should have had a contingency plan in place.
I agree.  The contingency plan should be to tow it out of sea lanes and to provide a means to safely sink it.  This thing is probably costing them more money to salvage than it would cost to pull to deep water and sink.  Or, better yet, modify the software to do a crash landing instead of a soft landing in such instances.

 - Ed Kyle
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: freda on 12/07/2018 02:14 pm
At this moment, a view of the booster on the Two Palms webcam. http://twopalms.com
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vanoord on 12/07/2018 02:17 pm
Not sure why this is such a difficult problem to solve. SpaceX owns a MARMAC barge, this is designed to do things like this.. Drive lift crane onto OCISLY, dispatch to booster w/ tug, Lift booster on to deck, return to dock, drive crane off OCISLY, deal with booster.....

It's like watching mimes in a box... guys... there IS no box.

There is a similar barge with a crane or excavator currently maintaining the Port Canaveral channel as we speak.... so don't say it can't be done. 

There's no way of getting any big crane onto OCISLY as the barge has deck extensions which will not take much weight.

It's much simpler to bring the booster into the port and deal with it there.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vanoord on 12/07/2018 02:22 pm
I agree.  The contingency plan should be to tow it out of sea lanes and to provide a means to safely sink it.  This thing is probably costing them more money to salvage than it would cost to pull to deep water and sink.  Or, better yet, modify the software to do a crash landing instead of a soft landing in such instances.

The grid fins are worth recovering and will more than cover the cost of the salvage operation.

Future contingency plans may well involve sinking the core (after removal of grid fins and perhaps legs) but this time SpaceX have the opportunity to recover a core and assess the effects of 2 days floating to see whether they are worth recovering in future.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Steve D on 12/07/2018 02:24 pm
From looking at the two palms webcam it seems to be under tow right now
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Step55 on 12/07/2018 02:24 pm
After the last time they soft landed a booster in the water, they should have had a contingency plan in place.
I agree.  The contingency plan should be to tow it out of sea lanes and to provide a means to safely sink it.  This thing is probably costing them more money to salvage than it would cost to pull to deep water and sink.  Or, better yet, modify the software to do a crash landing instead of a soft landing in such instances.

 - Ed Kyle

Would there be a security issue with leaving almost pristine Merlin 1Ds in shallow water?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/07/2018 02:32 pm
After the last time they soft landed a booster in the water, they should have had a contingency plan in place.
I agree.  The contingency plan should be to tow it out of sea lanes and to provide a means to safely sink it.  This thing is probably costing them more money to salvage than it would cost to pull to deep water and sink.  Or, better yet, modify the software to do a crash landing instead of a soft landing in such instances.

 - Ed Kyle

Would there be a security issue with leaving almost pristine Merlin 1Ds in shallow water?

Nah, the guys from BO would probably get to it first, and they have all the required clearances >;>>>
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: SimonFD on 12/07/2018 02:45 pm
From looking at the two palms webcam it seems to be under tow right now


The stage has exited stage-right (pun intended) :)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: joncz on 12/07/2018 02:51 pm
VoldeCam just went passive-aggressive

{and I've been clicking through their ads from time to time}
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ValmirGP on 12/07/2018 02:54 pm
A note to our newer members. In the past that webcam operator was very unhappy with us space fans. I suggest to NOT post any screen shots from their cam (they actually forbid it and your posts will be deleted if you do post images) and refrain from linking to them. We used to reference to them as the "web cam that shall not be named".

PS: Welcome to the forum :)

Good to finally know the history behind this. I'm not so knew to the forum and have seen mentions to this web cam from time to time and was curious about the "shall not be named" thing, but not so much so as to take the time to ask.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RoboGoofers on 12/07/2018 02:55 pm
Not sure why this is such a difficult problem to solve. SpaceX owns a MARMAC barge, this is designed to do things like this.. Drive lift crane onto OCISLY, dispatch to booster w/ tug, Lift booster on to deck, return to dock, drive crane off OCISLY, deal with booster.....

It's like watching mimes in a box... guys... there IS no box.

There is a similar barge with a crane or excavator currently maintaining the Port Canaveral channel as we speak.... so don't say it can't be done. 

There's no way of getting any big crane onto OCISLY as the barge has deck extensions which will not take much weight.

It's much simpler to bring the booster into the port and deal with it there.

OCISLY has probably got too much valuable equipment on it for this, but i thought that they could fill some of the compartments with water to partially submerge one side and then scoop up stuff.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Joffan on 12/07/2018 03:04 pm
OCISLY has probably got too much valuable equipment on it for this, but i thought that they could fill some of the compartments with water to partially submerge one side and then scoop up stuff.

You might be able to do something subtle with a tilted barge, dragging the (legs-off)) stage onto rollers and maybe moving  your pulling engine to control center of mass. But would definitely need to be slowly and definitely only in sheltered waters.

A straight (multi-)crane op is far more likely.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Semmel on 12/07/2018 03:05 pm
A note to our newer members. In the past that webcam operator was very unhappy with us space fans. I suggest to NOT post any screen shots from their cam (they actually forbid it and your posts will be deleted if you do post images) and refrain from linking to them. We used to reference to them as the "web cam that shall not be named".

PS: Welcome to the forum :)

Good to finally know the history behind this. I'm not so knew to the forum and have seen mentions to this web cam from time to time and was curious about the "shall not be named" thing, but not so much so as to take the time to ask.

Go back to the thread of the first booster recovery at sea and you find it in all its glory. Was some messy business and some people, not connected to this forum, got overexcited and pulled some (illegal) content grabbing. Thus bypassing the advertisement on their web page. This lead to the operator getting _very_ annoyed with space geeks in general and legal consequences were named. I dont remember any actual repercussions though. We try to stay away from them if possible.

I would love to grab my dinner at Fishlips today. Too bad I live a few thousand km away..
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/07/2018 03:11 pm
A note to our newer members. In the past that webcam operator was very unhappy with us space fans. I suggest to NOT post any screen shots from their cam (they actually forbid it and your posts will be deleted if you do post images) and refrain from linking to them. We used to reference to them as the "web cam that shall not be named".

PS: Welcome to the forum :)

Good to finally know the history behind this. I'm not so knew to the forum and have seen mentions to this web cam from time to time and was curious about the "shall not be named" thing, but not so much so as to take the time to ask.

Go back to the thread of the first booster recovery at sea and you find it in all its glory. Was some messy business and some people, not connected to this forum, got overexcited and pulled some (illegal) content grabbing. Thus bypassing the advertisement on their web page. This lead to the operator getting _very_ annoyed with space geeks in general and legal consequences were named. I dont remember any actual repercussions though. We try to stay away from them if possible.

I would love to grab my dinner at Fishlips today. Too bad I live a few thousand km away..
Perhaps they deliver...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: IntoTheVoid on 12/07/2018 03:16 pm
A note to our newer members. In the past that webcam operator was very unhappy with us space fans. I suggest to NOT post any screen shots from their cam (they actually forbid it and your posts will be deleted if you do post images) and refrain from linking to them. We used to reference to them as the "web cam that shall not be named".

PS: Welcome to the forum :)

Good to finally know the history behind this. I'm not so knew to the forum and have seen mentions to this web cam from time to time and was curious about the "shall not be named" thing, but not so much so as to take the time to ask.

Go back to the thread of the first booster recovery at sea and you find it in all its glory. Was some messy business and some people, not connected to this forum, got overexcited and pulled some (illegal) content grabbing. Thus bypassing the advertisement on their web page. This lead to the operator getting _very_ annoyed with space geeks in general and legal consequences were named. I dont remember any actual repercussions though. We try to stay away from them if possible.

I would love to grab my dinner at Fishlips today. Too bad I live a few thousand km away..
Perhaps they deliver...
Perhaps... But, they've out-sourced the delivery of the view, and the issues are with their chosen contractor. ;)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/07/2018 03:22 pm
Some construction barge might be mucking-up things...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: sghill on 12/07/2018 03:30 pm
Harbormaster: "Inbound high-priority tug and tow. Stay out of the channel."
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kevinof on 12/07/2018 03:35 pm
I see The Verge has a piece on this launch. More about the affordability of the loss than the actual loss itself.

https://www.theverge.com/2018/12/7/18129539/spacex-falcon-9-rocket-water-landing-valuation-investors (https://www.theverge.com/2018/12/7/18129539/spacex-falcon-9-rocket-water-landing-valuation-investors)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: pb2000 on 12/07/2018 03:38 pm
https://twitter.com/Cygnusx112/status/1071081139299905537


Edit: The interstage did indeed get busted up pretty bad.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: cartman on 12/07/2018 03:41 pm
How hard would it be to try to estimate the empty weight of the stage from these photos?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RoboGoofers on 12/07/2018 03:47 pm
How hard would it be to try to estimate the empty weight of the stage from these photos?
a very simple displacement calculator; will give a bad estimate:
http://www.blueheronwings.com/bh/comps/bdesign.html

~18 metric tons?

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: joncz on 12/07/2018 03:50 pm
😂

There's a *rocket* being towed into port and the highlight of one guy's day on the radio chatter was landing eleven mackerel.

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: pb2000 on 12/07/2018 03:54 pm
I guess the lifting cap is out of the question on this one... how the heck are they gonna get it on the stand?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: joncz on 12/07/2018 03:59 pm
I guess the lifting cap is out of the question on this one... how the heck are they gonna get it on the stand?

There was mention on the radio of a pair of cranes.  Sounds like they'll sling it out, and I guess remove the legs with another crane and cherry-picker, then place it directly on the trailer.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vanoord on 12/07/2018 04:02 pm
Lift it with two cranes and keep it horizontal would be my guess - but that would need the fourth leg either removed already or remove it while the booster is hanging.

Then
- put the stage down horizontally to get the remaining legs off and then lift it onto the transporter
or
- remove the other legs while it's hanging from the crane and then put it on the transporter
or
- put it on the transport and the remove the other three legs (which may be impossible depending how the attachment on the transporter works)

Arguably they could sling from the grid fins (if all four are still there) but unless they know the fins can take the weight, that could be risky.

It would also be possible to attach ropes to the octaweb, run the ropes to a single point above the top of the stage  and then sling round the stage under the grid fines to anchor the ropes against the side of the booster - I've seen boat masts lifted that way, but I'm not sure I'd like to try it with a rocket booster!
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OnWithTheShow on 12/07/2018 04:02 pm
I would guess they might attach the lifting ring they usually use in the HIF
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/07/2018 04:04 pm
Lift it with two cranes and keep it horizontal would be my guess - but that would need the fourth leg either removed already or remove it while the booster is hanging.

Then
- put the stage down horizontally to get the remaining legs off and then lift it onto the transporter
or
- remove the other legs while it's hanging from the crane and then put it on the transporter
or
- put it on the transport and the remove the other three legs (which may be impossible depending how the attachment on the transporter works)

Arguably they could sling from the grid fins (if all four are still there) but unless they know the fins can take the weight, that could be risky.

It would also be possible to attach ropes to the octaweb, run the ropes to a single point above the top of the stage  and then sling round the stage under the grid fines to anchor the ropes against the side of the booster - I've seen boat masts lifted that way, but I'm not sure I'd like to try it with a rocket booster!

The leg that was underwater was removed by divers yesterday.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: chrisking0997 on 12/07/2018 04:04 pm
I guess the lifting cap is out of the question on this one... how the heck are they gonna get it on the stand?

There was mention on the radio of a pair of cranes.  Sounds like they'll sling it out, and I guess remove the legs with another crane and cherry-picker, then place it directly on the trailer.
 

 With the interstage damaged, how are they going to put it on the transporter?  The attachment ring runs around the interstage.   
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: StuffOfInterest on 12/07/2018 04:07 pm
I guess the lifting cap is out of the question on this one... how the heck are they gonna get it on the stand?

There was mention on the radio of a pair of cranes.  Sounds like they'll sling it out, and I guess remove the legs with another crane and cherry-picker, then place it directly on the trailer.
 

 With the interstage damaged, how are they going to put it on the transporter?  The attachment ring runs around the interstage.   

I would guess either some cribbing or bags just back of the interstage and then a lot of bungy cords so it doesn't roll off.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/07/2018 04:09 pm
The images in this tweet are worth looking at in full screen!! There's an excellent shot of the interior of the interstage.

https://twitter.com/johnkrausphotos/status/1071083985537851392
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mme on 12/07/2018 04:15 pm
After the last time they soft landed a booster in the water, they should have had a contingency plan in place.
I agree.  The contingency plan should be to tow it out of sea lanes and to provide a means to safely sink it.  This thing is probably costing them more money to salvage than it would cost to pull to deep water and sink.  Or, better yet, modify the software to do a crash landing instead of a soft landing in such instances.

 - Ed Kyle
I don't think this recovery is about saving money, I think it's about collecting information.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/07/2018 04:15 pm
I guess the lifting cap is out of the question on this one... how the heck are they gonna get it on the stand?

There was mention on the radio of a pair of cranes.  Sounds like they'll sling it out, and I guess remove the legs with another crane and cherry-picker, then place it directly on the trailer.
 

 With the interstage damaged, how are they going to put it on the transporter?  The attachment ring runs around the interstage.   

I would guess either some cribbing or bags just back of the interstage and then a lot of bungy cords so it doesn't roll off.
A little force and some ratchet-straps might work. Not like it going to damage it more than it is...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/07/2018 04:21 pm
After the last time they soft landed a booster in the water, they should have had a contingency plan in place.
I agree.  The contingency plan should be to tow it out of sea lanes and to provide a means to safely sink it.  This thing is probably costing them more money to salvage than it would cost to pull to deep water and sink.  Or, better yet, modify the software to do a crash landing instead of a soft landing in such instances.

 - Ed Kyle
I don't think this recovery is about saving money, I think it's about collecting information.

Ahem... Grid fins. What people forget is that now that SpaceX has a higher confidence of getting the boosters back, they are putting more expensive components on them. Grid fins being the prime example, but there is probably more components on there that they will use on another flight.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mme on 12/07/2018 04:28 pm
...
I don't think this recovery is about saving money, I think it's about collecting information.

Ahem... Grid fins. What people forget is that now that SpaceX has a higher confidence of getting the boosters back, they are putting more expensive components on them. Grid fins being the prime example, but there is probably more components on there that they will use on another flight.
Yeah, totally true and I feel silly. :facepalm:

I still think they'd want the pieces back even if there was no hope of salvaging them.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Greg Hullender on 12/07/2018 04:30 pm
Why didn't it rupture and blow up when it tipped over? From the blooper reel, it looks like the first stage blew up on all previous failed landings (even ones in the water) when it tipped over.

Forgive me if this has already been asked and answered, but I looked back through two days of posts and didn't see it.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kevinof on 12/07/2018 04:32 pm
I think the low speed as it settled into the sea helped, also there was little if any horizontal velocity that would have put additional pressure on the stage.

or just plain luck?

Why didn't it rupture and blow up when it tipped over? From the blooper reel, it looks like the first stage blew up on all previous failed landings (even ones in the water) when it tipped over.

Forgive me if this has already been asked and answered, but I looked back through two days of posts and didn't see it.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: BunkerTheHusky on 12/07/2018 04:33 pm
We always here about how many times these rockets can be reflown, but has it ever been stated or predicted how many times the titanium grid fins can be reflown without replacement? That would really put into perspective how valuable they are to SpaceX to get back
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/07/2018 04:36 pm
After the last time they soft landed a booster in the water, they should have had a contingency plan in place.
I agree.  The contingency plan should be to tow it out of sea lanes and to provide a means to safely sink it.  This thing is probably costing them more money to salvage than it would cost to pull to deep water and sink.  Or, better yet, modify the software to do a crash landing instead of a soft landing in such instances.

 - Ed Kyle
I don't think this recovery is about saving money, I think it's about collecting information.

Ahem... Grid fins. What people forget is that now that SpaceX has a higher confidence of getting the boosters back, they are putting more expensive components on them. Grid fins being the prime example, but there is probably more components on there that they will use on another flight.

They'll want to recover the COPV v2.0s, certainly
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: envy887 on 12/07/2018 04:36 pm
At least some of the grid fins will fly again. (They are expensive as hell.)

This recovery effort is worth it just to get the fins back.

As for the rest of it, the damage caused by immersion in sea water can be massively reduced by action taken immediately after recovery - for something like a boat engine, that means strip down, wash down and coat in oil as soon as practically possible. If things are left, even for a couple of days, that's usually enough to finish them off.

Anything electrical will be a write-off straight away. For example, water gets down the inside of wires and that's made worse if there's any current in it when it's immersed: even though wires might look okay, they can fail 6, 12, 18 months later. Not the end of the world if it's a little outboard motor on a boat, but a big problem if it's part of a rocket.

They can probably strip it down to bare metal tanks and octaweb, rebuild it with new electronics, engines, and pneumatics etc, and still be cheaper than a new one.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/07/2018 04:37 pm
We always here about how many times these rockets can be reflown, but has it ever been stated or predicted how many times the titanium grid fins can be reflown without replacement? That would really put into perspective how valuable they are to SpaceX to get back

Elon Musk has said they can be reused indefinitely. Titanium is very robust.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: DigitalMan on 12/07/2018 04:46 pm
After the last time they soft landed a booster in the water, they should have had a contingency plan in place.
I agree.  The contingency plan should be to tow it out of sea lanes and to provide a means to safely sink it.  This thing is probably costing them more money to salvage than it would cost to pull to deep water and sink.  Or, better yet, modify the software to do a crash landing instead of a soft landing in such instances.

 - Ed Kyle
I don't think this recovery is about saving money, I think it's about collecting information.

Ahem... Grid fins. What people forget is that now that SpaceX has a higher confidence of getting the boosters back, they are putting more expensive components on them. Grid fins being the prime example, but there is probably more components on there that they will use on another flight.

They'll want to recover the COPV v2.0s, certainly

I thought Hans said the COPV 2.0s were only on stage 2.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/07/2018 04:48 pm
Thank you Tom!! :)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RoboGoofers on 12/07/2018 04:54 pm
Why didn't it rupture and blow up when it tipped over? From the blooper reel, it looks like the first stage blew up on all previous failed landings (even ones in the water) when it tipped over.

Forgive me if this has already been asked and answered, but I looked back through two days of posts and didn't see it.

the sea state probably has a lot to do with it.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: webdan on 12/07/2018 04:55 pm
I've managed to crop out the detail from inside the interstage. Check out what the arrow points to.

Also really cool to finally observe, the hydraulic actuators for the fins. You can clearly see 3 of them and how they are  arranged in a push/pull configuration.

Edit: Original from John Kraus
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Joffan on 12/07/2018 04:59 pm
Why didn't it rupture and blow up when it tipped over? From the blooper reel, it looks like the first stage blew up on all previous failed landings (even ones in the water) when it tipped over.

Forgive me if this has already been asked and answered, but I looked back through two days of posts and didn't see it.

the sea state probably has a lot to do with it.
I'd say that's the least likely factor to save the stage. I'd say the stage came in close enough to vertical that it went in fairly deep and could start its topple slowly. It may even have been helped by the fact that it had just rotated past vertical, so was slightly "pre-toppled".

Alternative non-serious hypothesis: the stage has to be spinning to survive.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Orbiter on 12/07/2018 05:01 pm
This is new -- looks like SpaceX will be doing a webcast for the CRS-16 rendezvous (maybe it'll just be a rehost of the NASA stream):

https://www.youtube.com/watch?v=fDJ6A-0jpkE
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: pb2000 on 12/07/2018 05:01 pm
I've managed to crop out the detail from inside the interstage. Check out what the arrow points to.

Also really cool to finally observe, the hydraulic actuators for the fins. You can clearly see 3 of them and how they are  arranged in a push/pull configuration.
I'll have to dig up the article where I got the picture to give it proper image credit, but we've already seen inside an interstage.

Edit: image credit https://www.bloomberg.com/news/features/2018-07-26/she-launches-spaceships-sells-rockets-and-deals-with-elon-musk
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Mike_1179 on 12/07/2018 05:02 pm
I've managed to crop out the detail from inside the interstage. Check out what the arrow points to.


That is one of the supports for the "pusher" that extends out to guide the MVac (+ nozzle extension) out of the interstage during stage separation, right?

If its the same design as the one in the picture posted above (with Shotwell in front of it) you see that support is attached to the top of the stage 1 tank. Wonder what made it buckle.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Johnnyhinbos on 12/07/2018 05:04 pm
Based on radio chatter I was thinking that they were going to haul the booster out upside down by the hold downs. However there was just mention of needing the divers to put in a "belly pan", which has eluded me...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: pb2000 on 12/07/2018 05:05 pm
If its the same design as the one in the picture posted above (with Shotwell in front of it) you see that support is attached to the top of the stage 1 tank. Wonder what made it buckle.
Probably the missing part of the interstage was pushed into it.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vanoord on 12/07/2018 05:06 pm
They can probably strip it down to bare metal tanks and octaweb, rebuild it with new electronics, engines, and pneumatics etc, and still be cheaper than a new one.

Given the potential for the tanks to have been strained in unusual ways, I don't see a future for them other than being dismantled for inspection.

Even if used for a SpaceX test flight, there's still a risk to the pad if they try to fly it again - unless it's shipped to MacGregor and used to see if they can take off with legs folded down... now there's an idea!  ;D
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: webdan on 12/07/2018 05:08 pm
I've managed to crop out the detail from inside the interstage. Check out what the arrow points to.

Also really cool to finally observe, the hydraulic actuators for the fins. You can clearly see 3 of them and how they are  arranged in a push/pull configuration.
I'll have to dig up the article where I got the picture to give it proper image credit, but we've already seen inside an interstage.

Edit: image credit https://www.bloomberg.com/news/features/2018-07-26/she-launches-spaceships-sells-rockets-and-deals-with-elon-musk

Ah yes, missed that picture, thanks for sharing. Notice that the fin arms aren't attached yet. From that perspective you can plainly see how flat those arms are. Also someone is being crushed by the rocket :)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Joffan on 12/07/2018 05:08 pm
If its the same design as the one in the picture posted above (with Shotwell in front of it) you see that support is attached to the top of the stage 1 tank. Wonder what made it buckle.
Probably the missing part of the interstage was pushed into it.
Yes, I'm sure the flap went in first before it was dragged to its current out position. I'm not sure there's anything large part missing; we'll see today or tomorrow I guess.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RoboGoofers on 12/07/2018 05:08 pm
Why didn't it rupture and blow up when it tipped over? From the blooper reel, it looks like the first stage blew up on all previous failed landings (even ones in the water) when it tipped over.

Forgive me if this has already been asked and answered, but I looked back through two days of posts and didn't see it.

the sea state probably has a lot to do with it.
I'd say that's the least likely factor to save the stage. I'd say the stage came in close enough to vertical that it went in fairly deep and could start its topple slowly. It may even have been helped by the fact that it had just rotated past vertical, so was slightly "pre-toppled".

Alternative non-serious hypothesis: the stage has to be spinning to survive.

i mean if it falls across a swell, like a 'backbreaker' move in wrestling.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Slarty1080 on 12/07/2018 05:16 pm
Is there any information as to what caused this recovery failure?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ellindsey on 12/07/2018 05:18 pm
Is there any information as to what caused this recovery failure?
Hydraulic pump motor stalled.  Which caused the grid fins to all lock in place immobile during the descent process.  The rocket was unable to navigate to the landing site, and picked up a significant spin during descent.

What caused the pump motor to stall is yet to be determined, they'll probably have to get it on land and take it apart to tell.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: HVM on 12/07/2018 05:38 pm
Is there any information as to what caused this recovery failure?
Hydraulic pump motor stalled.  Which caused the grid fins to all lock in place immobile during the descent process.  The rocket was unable to navigate to the landing site, and picked up a significant spin during descent.

What caused the pump motor to stall is yet to be determined, they'll probably have to get it on land and take it apart to tell.

"A leading cause of many hydraulic pump failures is hydraulic fluid contamination". In freezing condition it can be water. Maybe SpX tell us, maybe not. It's SpX internal investigation, or with NASA?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: deruch on 12/07/2018 05:51 pm
Why didn't it rupture and blow up when it tipped over? From the blooper reel, it looks like the first stage blew up on all previous failed landings (even ones in the water) when it tipped over.

Forgive me if this has already been asked and answered, but I looked back through two days of posts and didn't see it.

Seems to actually be closer to 50/50 for soft touchdowns in the water living past tipping over.  We know from the video recovery effort that CRS-3 survived toppling.  So did GovSat-1/SES-16 (the one that got used for target practice).  I seem to recall another instance where Elon talked about sending out recovery vessels to try to pick up a soft landed core in the water which survived toppling, but that it sank before they could get to it possibly due to heavy weather/waves (maybe CRS-4?). 
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Barrie on 12/07/2018 06:15 pm
  It's SpX internal investigation, or with NASA?

As booster recovery isn't a NASA requirement, I assume it is a purely SpaceX investigation
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kevinof on 12/07/2018 06:25 pm
Presume it's only SpaceX involved as Nasa have nothing to do with the landing. I also wouldn't call it an "investigation" as that sounds very formal. They will take the pump apart, find the fault and make a change to make sure it doesn't happen again.

Is there any information as to what caused this recovery failure?
Hydraulic pump motor stalled.  Which caused the grid fins to all lock in place immobile during the descent process.  The rocket was unable to navigate to the landing site, and picked up a significant spin during descent.

What caused the pump motor to stall is yet to be determined, they'll probably have to get it on land and take it apart to tell.

"A leading cause of many hydraulic pump failures is hydraulic fluid contamination". In freezing condition it can be water. Maybe SpX tell us, maybe not. It's SpX internal investigation, or with NASA?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/07/2018 06:29 pm
To pull it out of the water by crane they need attachment points both at bottom and top. Bottom.is obvious: hold down clamp latches.
top would usually go on that interstage crane adapter. Thats not an option, but the grid fin attachment mounts should be able to take the load, too. It might make sense to remove the grid fins first and attach some hooks to the mounts instead, them run a cable or sling through for the crane.

If they rotate the damaged part to the top, then the stage should be able to rest in the bottom half cradle of the transporter truck around the intact half of the interstage.

Not very secure, but its not that far from pier to their hangar, is it?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/07/2018 06:49 pm
I don't see any reason the could not lift around the grid-fin mount area, it is robust to take the aero loads there from them. Remove them for safe keeping and install lift pins in place...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: MechE31 on 12/07/2018 07:01 pm
Remember that during processing, the first stage is lifted at various stages of build flow, perhaps without an interstage.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: edkyle99 on 12/07/2018 07:06 pm
Long ago, SpaceX lifted the Falcon 9 proto-stage like this.

 - Ed Kyle
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: guckyfan on 12/07/2018 07:08 pm
I don't see any reason the could not lift around the grid-fin mount area, it is robust to take the aero loads there from them. Remove them for safe keeping and install lift pins in place...

The interstage is damaged. I would not want to lift the stage that way.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: lonestriker on 12/07/2018 07:12 pm
I don't see any reason the could not lift around the grid-fin mount area, it is robust to take the aero loads there from them. Remove them for safe keeping and install lift pins in place...

The interstage is damaged. I would not want to lift the stage that way.

Lifting the booster out of the water really isn't rocket science. Just use a strap under the top portion (below the interstage) and however they normally attach the bottom. This isn't flight hardware now so you can just jury-rig something together that gets it up in one piece.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/07/2018 07:13 pm
I don't see any reason the could not lift around the grid-fin mount area, it is robust to take the aero loads there from them. Remove them for safe keeping and install lift pins in place...

The interstage is damaged. I would not want to lift the stage that way.

The damage appears. To ve only above the grid fins,which are at the bottom of the interstage. But you'd haveto inspect if there are smaller fractures makibg thus unsafe. A belt around the tank section would work but then they need to make sure they lift even so it wont slide either way. Sounds easy enough, but that thing is big ;) and in the water.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/07/2018 07:17 pm
I don't see any reason the could not lift around the grid-fin mount area, it is robust to take the aero loads there from them. Remove them for safe keeping and install lift pins in place...

The interstage is damaged. I would not want to lift the stage that way.

The damage appears. To ve only above the grid fins,which are at the bottom of the interstage. But you'd haveto inspect if there are smaller fractures makibg thus unsafe. A belt around the tank section would work but then they need to make sure they lift even so it wont slide either way. Sounds easy enough, but that thing is big ;) and in the water.

Two-crane lifts require good coordination, but are not unusual.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/07/2018 07:19 pm
I don't see any reason the could not lift around the grid-fin mount area, it is robust to take the aero loads there from them. Remove them for safe keeping and install lift pins in place...

The interstage is damaged. I would not want to lift the stage that way.
It's below the interstage...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: guckyfan on 12/07/2018 07:21 pm
I don't see any reason the could not lift around the grid-fin mount area, it is robust to take the aero loads there from them. Remove them for safe keeping and install lift pins in place...

The interstage is damaged. I would not want to lift the stage that way.
It's below the interstage...

The grid fins are mounted at the interstage.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: david1971 on 12/07/2018 07:21 pm
I rationally understand the physics and economics of the situation...  And I don't want to be yet another SLS-basher on NSF...  But watching this entire recovery process makes me sad for all of those magnificent SSMEs we are going to send to the bottom of the ocean.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mlindner on 12/07/2018 07:26 pm
SpaceX will do a live coverage of CRS-16 Dragon rendezvous, arrival and capture at the ISS starting at 1:30am PST or 9:30 UTC on December 8th.

YouTube link here:

https://www.youtube.com/watch?v=fDJ6A-0jpkE

Has this ever happened before? I don't remember SpaceX ever doing live streams of berthings, even for the very first berthing. Wonder if something different is planned? It will be awesome if we get livestream from cameras on board the Dragon.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/07/2018 07:28 pm
I don't see any reason the could not lift around the grid-fin mount area, it is robust to take the aero loads there from them. Remove them for safe keeping and install lift pins in place...

The interstage is damaged. I would not want to lift the stage that way.
It's below the interstage...

The grid fins are mounted at the interstage.
They go through a circular structural member at the top of the tank for load paths...AFAIK. If you know of something other please let me know...

Edit to add:
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kdhilliard on 12/07/2018 07:34 pm
SpaceX will do a live coverage of CRS-16 Dragon rendezvous, arrival and capture at the ISS starting at 1:30am PST or 9:30 UTC on December 8th.
Has this ever happened before? I don't remember SpaceX ever doing live streams of berthings, even for the very first berthing. Wonder if something different is planned? It will be awesome if we get livestream from cameras on board the Dragon.

Perhaps they wanted some practice prior to the livestream of DM-1.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: cygnusx112 on 12/07/2018 09:08 pm
Here are some of my pictures from the booster return this morning.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: SDSmith on 12/07/2018 10:54 pm
Looking at the interstage the pusher looks a little racked. The top right strut looks bent and the bottom strut appears to be broken.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: AndyH on 12/07/2018 11:44 pm
It sounds like they're starting to take up the slack in the lifting strap at the interstage junction.  They're placing foam to protect the raceway.

https://www.broadcastify.com/listen/feed/21054/web (https://www.broadcastify.com/listen/feed/21054/web)

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: MKremer on 12/08/2018 12:19 am
Looking at the interstage the pusher looks a little racked. The top right strut looks bent and the bottom strut appears to be broken.

Appears to me that the side that is broken/slightly caved in was the side that struck the water almost on the grid fin when the stage fell over. The force caved in the composite around the mounting support and perhaps weakened the structure above it.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Wolfram66 on 12/08/2018 12:28 am
Looking at the interstage the pusher looks a little racked. The top right strut looks bent and the bottom strut appears to be broken.

Adjusted to show more detail w/ Photoshop Express App for iPad
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: leetdan on 12/08/2018 04:10 am
Caught some pictures from Gator's (fka Milliken's Reef) as the lift was happening...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Cheapchips on 12/08/2018 09:20 am

I've really enjoyed these recovery pictures.  Space hardware with people and everyday things surround them are some of my favourite images.  I think these are probably the best scale views we've had of an F9 with its legs out.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mainmind on 12/08/2018 10:14 am
Does anyone know the operational constraint that required the back-away from capture volume because Comm with the ground was going to go down? The astronauts are driving the SRMS and the Dragon is in closed-loop communications with the station directly. Why couldn't they press for capture and wait to continue berth operations until comm was restored? This seems really wasteful.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: cygnusx112 on 12/08/2018 12:19 pm
Booster out of the water and the crew is starting to show up. Should be interesting seeing the legs removed.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jakusb on 12/08/2018 12:22 pm
Booster out of the water and the crew is starting to show up. Should be interesting seeing the legs removed.

Why not post this in Update thread? ;)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jakusb on 12/08/2018 12:24 pm
Booster out of the water and the crew is starting to show up. Should be interesting seeing the legs removed.

Looks like the one leg collapsed backward and dented an engine bell...
Clearly not possible on impact, so most likely a failed attempt at pulling with a line from it?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/08/2018 12:45 pm
Booster out of the water and the crew is starting to show up. Should be interesting seeing the legs removed.

Looks like the one leg collapsed backward and dented an engine bell...
Clearly not possible on impact, so most likely a failed attempt at pulling with a line from it?

Why would it not be posible on impact, specifically during tipover if the leg broke off and the weight of the rocket came down on it? The dent lines up nicely with the way the leg bulges outward around the centerline.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kdhilliard on 12/08/2018 01:07 pm
Booster out of the water and the crew is starting to show up. Should be interesting seeing the legs removed.

Are the blue stands supporting the stage on either end something we have seen before?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jakusb on 12/08/2018 01:16 pm
Booster out of the water and the crew is starting to show up. Should be interesting seeing the legs removed.

Looks like the one leg collapsed backward and dented an engine bell...
Clearly not possible on impact, so most likely a failed attempt at pulling with a line from it?

Why would it not be posible on impact, specifically during tipover if the leg broke off and the weight of the rocket came down on it? The dent lines up nicely with the way the leg bulges outward around the centerline.

Because the leg would be pushed up against the side as the water would push it back up, not down...
Unless it made lateral move before falling over, but it clearly did not..
Also the piston would first have to come off before it would be able to hit the engine bell..
To me it correlates more with a failed attempt to attach a line to it and then ripping off the piston first and the leg falling down on the engine bell both by gravity and a tug pulling the line.

It also explains the clear instructions towards the recovery crew to absolutely NOT attach anything to the legs as they would break... I was wondering how they would be so clear minded on warning them in advance but now I think it might be a response to it actually being just experienced in practice..
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Wolfram66 on 12/08/2018 01:24 pm
Booster out of the water and the crew is starting to show up. Should be interesting seeing the legs removed.


Adjusted CygnusX112 for clarity & exposure
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Johnnyhinbos on 12/08/2018 02:11 pm
Some reflections...

- Clearly see the load spreader on the sling I referred to yesterday.

- Strange seeing the booster “post recovery” with the grid fins deployed.

- strange seeing the booster horizontal with (most) legs deployed.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: SDSmith on 12/08/2018 03:35 pm
I only see 3 grid fins.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: pb2000 on 12/08/2018 04:00 pm
In the interests of science and combustion instability testing (or just for sh|ts and giggles), I think that bent merlin needs to be hooked up on the test stand and fired one last time before its retired.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mainmind on 12/08/2018 04:32 pm
Does anyone know the operational constraint that required the back-away from capture volume because Comm with the ground was going to go down? The astronauts are driving the SRMS and the Dragon is in closed-loop communications with the station directly. Why couldn't they press for capture and wait to continue berth operations until comm was restored? This seems really wasteful.

Re-upping this question so it doesn't get lost among the booster recovery talk. What is the constraint that they had to do a Dragon back-away to the 30m hold when they weren't going to have TDRSS at the planned capture time? Abundance of caution? Is the command to send Dragon to free drift right before grapple coming in over TDRSS and not a direct command from ISS? It sounded  like the back-away command was sent from ISS.

Thank you
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ellindsey on 12/08/2018 04:33 pm
I only see 3 grid fins.
I think the fourth one is still there, just hidden behind the blue cradle that the booster is resting on.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/08/2018 04:35 pm
In the interests of science and combustion instability testing (or just for sh|ts and giggles), I think that bent merlin needs to be hooked up on the test stand and fired one last time before its retired.

If only test stands were as disposable.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/08/2018 04:54 pm
I only see 3 grid fins.
No you don't.
You see 2 grid fins.
The thIrd grin fin is behind the booster, not visible, on the other side and you assume its there because it was visible in earlier photos.

( But if they are actually working on removing the fins, we cannot simply assume that its there either )

The 4th grid fin would be on the bottom on the booster and currently hidden by that rack thongy they put underneath to support its weight.

From the current angle we can't tell if its there or not. It was not visible in previous photos since it was under water. ( or too dark )
So there is some mystery around it, but not enough evidence to say wether its actually missing ;)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: oiorionsbelt on 12/08/2018 05:59 pm
Is the similarity of shape between the grid fin attachment points and the "ice" that was liberated on ascent just a coincidence?

https://twitter.com/w00ki33
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/08/2018 06:06 pm
Is the similarity of shape between the grid fin attachment points and the "ice" that was liberated on ascent just a coincidence?

https://twitter.com/w00ki33

Probably not. That ice obviously formed around some sort of port in ring shape, so it matches that shape like a negative imprint. But its not necessarily from the grid fin attachment point. All 4 gridfins were still there, there would have been no way for it to cone off in one piece without the grid fin coming off first.

Are there umbilical attachments or other ports near or underneath the grid fins or at the botton.of the 1 st stage that have a similar shape?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 12/08/2018 06:10 pm
Is the similarity of shape between the grid fin attachment points and the "ice" that was liberated on ascent just a coincidence?

They're both ring-like, that's about it. The grid attachments actually have a cover on during flight which was apparently taken off here for purposes of fin removal.

It's more likely that the ice formed around one of the interstage vents that dumps various MVac GOX/LOX bleeds during prop load and 1st stage flight. I.e. the flexible hoses you can see flapping around inside the interstage after stage sep.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: deruch on 12/08/2018 06:16 pm
It's SpX internal investigation, or with NASA?

As booster recovery isn't a NASA requirement, I assume it is a purely SpaceX investigation

I'm pretty sure there will be some sort of landing mishap investigation.  It will likely be SpaceX only with possible involvement/positions for USAF Range Safety and the FAA as those are the two organizations responsible for approving RTLS landings operations.  And maybe an observer from NASA just to keep their hand in.  The technical focus of exactly what failed and why won't be of much interest to any one but SpaceX.  However a review of the performance of in-place safety rules/precautions for RTLS and an examination of potential areas of improvement or needed changes will be of interest to the other groups.  If Range Safety and FAA aren't actually represented on the board, for sure they will be CC'd on the report as well as be doing their own analysis as to safety impacts.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Patchouli on 12/08/2018 06:23 pm
In the interests of science and combustion instability testing (or just for sh|ts and giggles), I think that bent merlin needs to be hooked up on the test stand and fired one last time before its retired.

If only test stands were as disposable.
Yah it could damage the test stand.
Though I think just the nozzle extension is damaged which I think is replaceable.
If all else fails it could make an interesting lawn decoration for one of their buildings.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: gongora on 12/08/2018 06:38 pm
It's SpX internal investigation, or with NASA?

As booster recovery isn't a NASA requirement, I assume it is a purely SpaceX investigation

I'm pretty sure there will be some sort of landing mishap investigation.  It will likely be SpaceX only with possible involvement/positions for USAF Range Safety and the FAA as those are the two organizations responsible for approving RTLS landings operations.  And maybe an observer from NASA just to keep their hand in.  The technical focus of exactly what failed and why won't be of much interest to any one but SpaceX.  However a review of the performance of in-place safety rules/precautions for RTLS and an examination of potential areas of improvement or needed changes will be of interest to the other groups.  If Range Safety and FAA aren't actually represented on the board, for sure they will be CC'd on the report as well as be doing their own analysis as to safety impacts.

I agree with this, it would be a missed opportunity for the FAA and USAF ranges not to review what happened on this flight.  They definitely have an interest in the SpaceX landing processes.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/08/2018 07:00 pm
The thing is, something obviously went wrong. It didn't go "horribly" wrong. SpaceX inherently safe landing approach procedure worked, and some aspects of their flight control software got a very rare chance to demonstrate how awesome they are. It also demonstrated that propulsive landing can still work even if aerodynamic control fails ( that will come up again, when the discussion of propulsive versus horizontal airplane like landing comes up again, for example with that point 2 point passenger idea with BFR )

But ultimately this mishap will have had both root cause and contributing factors, some of which might affect launches too, not just landings.

Some component didn't work as it should have, and it wasn't noticed until that component was needed in flight.

Obviously adding redundancy might help. But if an investigation comes to the conclusion that overlooking something in assembly or during test procedures contributed to a faulty part ending up on an operational flight, this might end up with suggestions for operational, test or QC procedure changes that have implications for other flight hardware, relevant to commercial and possibly crewed launches too.

That does not necessarily mean someone did something wrong. Sometimes its just that theres a way stuff could have been done even better.

If SpaceX really wants to reach Air-travel-like reliability, they will want and have to go that route. And the more partners they could get into the investigation, the better. NASA, FAA, Airforce, NTSB even?

It doesn't look like they'd have to stand down or delay launches until the result of that investigation. After all, nothing bad happened and theres no indication that theres anything inherently wrong with SpaceX hardware or procedures. But that doesnt mean the investigation should be any less thorrough than if a launcher had blown up.

Its definitely going to be easier though. After all they recovered the core mostly intact and can look in depth at all data as well as the components itself. Should be fun.

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: weepingdragon on 12/08/2018 07:00 pm
Looks like the one leg collapsed backward and dented an engine bell...
Clearly not possible on impact, so most likely a failed attempt at pulling with a line from it?

Landing damage does seems wrong angle. Though landing could have done damage to that leg.

Likely leg caught on a sandbar (or bottom in shallow water). Gives right angle to damage engine bell.  And current/wind was really moving the booster south at a nice clip considering where/when it's movement was finally arrested compared to where it hit the water.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: weepingdragon on 12/08/2018 07:14 pm
Re-upping this question so it doesn't get lost among the booster recovery talk. What is the constraint that they had to do a Dragon back-away to the 30m hold when they weren't going to have TDRSS at the planned capture time? Abundance of caution? Is the command to send Dragon to free drift right before grapple coming in over TDRSS and not a direct command from ISS? It sounded  like the back-away command was sent from ISS.

Thank you

info probably over here SpaceX CRS-16 Dragon - RNDZ, ISS Ops, EOM - UPDATES (https://forum.nasaspaceflight.com/index.php?topic=46944.0)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mainmind on 12/08/2018 07:26 pm
Re-upping this question so it doesn't get lost among the booster recovery talk. What is the constraint that they had to do a Dragon back-away to the 30m hold when they weren't going to have TDRSS at the planned capture time? Abundance of caution? Is the command to send Dragon to free drift right before grapple coming in over TDRSS and not a direct command from ISS? It sounded  like the back-away command was sent from ISS.

Thank you

info probably over here SpaceX CRS-16 Dragon - RNDZ, ISS Ops, EOM - UPDATES (https://forum.nasaspaceflight.com/index.php?topic=46944.0)


Sadly no. It just notes the ground issue with TDRSS causing a retreat to the 30 meter hold from the capture box and later the resumption of approach to capture point. No explanation of why ISS to ground link is required to perform the capture with SSRMS. Good thought, but the mods seem to keep the "update" threads clean of extra info.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/08/2018 07:57 pm
It's SpX internal investigation, or with NASA?

As booster recovery isn't a NASA requirement, I assume it is a purely SpaceX investigation

I'm pretty sure there will be some sort of landing mishap investigation.  It will likely be SpaceX only with possible involvement/positions for USAF Range Safety and the FAA as those are the two organizations responsible for approving RTLS landings operations.  And maybe an observer from NASA just to keep their hand in.  The technical focus of exactly what failed and why won't be of much interest to any one but SpaceX.  However a review of the performance of in-place safety rules/precautions for RTLS and an examination of potential areas of improvement or needed changes will be of interest to the other groups.  If Range Safety and FAA aren't actually represented on the board, for sure they will be CC'd on the report as well as be doing their own analysis as to safety impacts.

I agree with this, it would be a missed opportunity for the FAA and USAF ranges not to review what happened on this flight.  They definitely have an interest in the SpaceX landing processes.

Absolutely.  And it's 100% in SpaceX's benefit for this investigations to happen, since SpaceX came out of this looking really good - there was an anomaly, and existing plans and designs worked, plus later the vehicle even saved itself, for extra credit.

When the time comes for P2P talks, this is as good a demonstrator SpaceX can have for their approach.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: RedLineTrain on 12/08/2018 08:06 pm
Really liked the rendezvous and berthing webcast.  Great dry-run for DM-1 & 2.  As a suggestion to SpaceX, it would be nice if there were some information on the screen:

*the speaker identified (as in many videoconference programs); and
*some sort of timeline or on-screen notations to indicate what is happening or about to happen, as on the launch webcasts.

Another suggestion:

*auto fade-in and fade-out on the music when speakers are talking.  Love to listen to the radio comms.

Overall, I thought the talking heads did a great job, but they narrated things a bit more heavily than is my taste over such a long webcast.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/08/2018 08:25 pm
https://www.youtube.com/watch?v=aVXJhrUyuTA
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: wannamoonbase on 12/08/2018 09:38 pm
After a nice salty soak and the initial quenching it’s hard to see how this bird flys again.

But I want to see them try.  Just recovering it is impressive.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Mixi55 on 12/08/2018 09:48 pm
Great video - Falcon 9 booster landing in ocean with music from the "Interstellar".
The descent looks even more suspenseful and exciting this way  :)

https://www.youtube.com/watch?v=ObRfjxN9M_Y

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: webdan on 12/08/2018 09:57 pm
Interesting video analysis, his voice reminds me of Craig Ferguson.

I'm agreeing with most except where the fins actually do operate as he mentions.

In other words, I would have thought that each is individually controlled, because they do have separate actuators.

If not, does anybody have any reference so I can update my mental knowledge base? Thanks!
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: JBF on 12/08/2018 10:48 pm
Interesting video analysis, his voice reminds me of Craig Ferguson.

I'm agreeing with most except where the fins actually do operate as he mentions.

In other words, I would have thought that each is individually controlled, because they do have separate actuators.

If not, does anybody have any reference so I can update my mental knowledge base? Thanks!

They are individually controlled, but there is only 1 pump to pressurize the system.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Joffan on 12/08/2018 10:57 pm
Interesting video analysis, his voice reminds me of Craig Ferguson.

I'm agreeing with most except where the fins actually do operate as he mentions.

In other words, I would have thought that each is individually controlled, because they do have separate actuators.

If not, does anybody have any reference so I can update my mental knowledge base? Thanks!
As far as I can tell, grid fins have individual actuation (and they wouldn't be very useful without that). For the divert maneuver, they would likely operate roughly in the way that Scott Manley described,  with one pair driving the pitch-over to retarget onto the landing pad, although that wouldn't be the only way they could operate. Based on Elon's remarks since the failure, all the fins are supplied with pressure fluid from a common hydraulic reservoir which is pressurized with just the one pump.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: AndyH on 12/09/2018 01:14 am
Re-upping this question so it doesn't get lost among the booster recovery talk. What is the constraint that they had to do a Dragon back-away to the 30m hold when they weren't going to have TDRSS at the planned capture time? Abundance of caution? Is the command to send Dragon to free drift right before grapple coming in over TDRSS and not a direct command from ISS? It sounded  like the back-away command was sent from ISS.

Thank you

info probably over here SpaceX CRS-16 Dragon - RNDZ, ISS Ops, EOM - UPDATES (https://forum.nasaspaceflight.com/index.php?topic=46944.0)


Sadly no. It just notes the ground issue with TDRSS causing a retreat to the 30 meter hold from the capture box and later the resumption of approach to capture point. No explanation of why ISS to ground link is required to perform the capture with SSRMS. Good thought, but the mods seem to keep the "update" threads clean of extra info.
Apparently the arm is at least initially controlled from the ground, and there was a ground failure that prevented the TDRS link required.  They moved Dragon back until the ground crew had a good satellite link, then they resumed the process.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: MattBaker on 12/09/2018 01:17 am
Well, they didn't let them do an RTLS at Vandenberg earlier this week in case something happens, I wonder how the Air Force looks at that decision after this failure.

On the one hand if the exact same failure happens, seems like there's no danger to Vandenberg at all, the stage just lands in the Pacific (that recovery would be worse though, seeing as the West Coast SpaceX fleet is based further away than "just pop down the road"-Cape Canaveral).

On the other hand, if something happens a couple of minutes later during the landing burn or something else just doesn't work in general...sure shows there'll always be some danger to this whole thing.

Actually now that I think about it, having your landing site be directly next to your launch pad is probably convenient but if something goes wrong...especially at your only West Coast pad compared to the two Florida pads you have...well, I hope all their failures end as smoothly and entertainingly as this one.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/09/2018 06:20 am
Well, they didn't let them do an RTLS at Vandenberg earlier this week in case something happens, I wonder how the Air Force looks at that decision after this failure.

On the one hand if the exact same failure happens, seems like there's no danger to Vandenberg at all, the stage just lands in the Pacific (that recovery would be worse though, seeing as the West Coast SpaceX fleet is based further away than "just pop down the road"-Cape Canaveral).

On the other hand, if something happens a couple of minutes later during the landing burn or something else just doesn't work in general...sure shows there'll always be some danger to this whole thing.

Actually now that I think about it, having your landing site be directly next to your launch pad is probably convenient but if something goes wrong...especially at your only West Coast pad compared to the two Florida pads you have...well, I hope all their failures end as smoothly and entertainingly as this one.
We know the answer to your first question.

The stage doesn't shift the IIP onto shore until the main engine relight happens and the engine is confirmed good.

We can also assume that any other health checks that fail also result in an offshore landing.

They can also walk the IIP along a safe corridor as it approaches the landing pad.  There's no reason that the post-relight path must be collinear with the pre-relight path.

-----
ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: MattBaker on 12/09/2018 07:49 am
What if the hydraulic pump stalls during the final main engine relight? Especially during the transition of the landing point so it can't stabilise to stop lateral movement?

Which of course is an unfair question because we don't know what caused it or what the stage's reaction to it would be so I can use the hydraulics as "magical failure turning this into dangerous hypothetical that probably never happens".

But when their secret billion dollar projects are on the line the Air Force can probably be pretty unfair, too.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/09/2018 09:18 am
What if the hydraulic pump stalls during the final main engine relight? Especially during the transition of the landing point so it can't stabilise to stop lateral movement?

Which of course is an unfair question because we don't know what caused it or what the stage's reaction to it would be so I can use the hydraulics as "magical failure turning this into dangerous hypothetical that probably never happens".

But when their secret billion dollar projects are on the line the Air Force can probably be pretty unfair, too.

Actually, we had that before. Remember a certain drone ship landing that grid fins went into hardover due to lack of hydraulic fluid?

The stage still managed to hit the deck of the ship, but wasn't able to land. If it can hit the deck then it can certainly hit its landing pad.

The drone ship mishaps provide a useful case study for minimum safe distance and debris impacts. I think the COPV reach the furthest since they are mini-helium-rockets in their own right ;)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: MattBaker on 12/09/2018 12:02 pm
Oh man, that was, what, 30 launches ago? Forgot about that.

Hope we never have to find out what's the worst case on the West Coast then because it's pretty close (https://cdn.teslarati.com/wp-content/uploads/2018/09/SLC-4E-overview-3-1.jpg) from the landing pad to everything else, the Cape is sorta more forgiving there.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jcc on 12/09/2018 02:09 pm
Interesting video analysis, his voice reminds me of Craig Ferguson.

I'm agreeing with most except where the fins actually do operate as he mentions.

In other words, I would have thought that each is individually controlled, because they do have separate actuators.

If not, does anybody have any reference so I can update my mental knowledge base? Thanks!
As far as I can tell, grid fins have individual actuation (and they wouldn't be very useful without that). For the divert maneuver, they would likely operate roughly in the way that Scott Manley described,  with one pair driving the pitch-over to retarget onto the landing pad, although that wouldn't be the only way they could operate. Based on Elon's remarks since the failure, all the fins are supplied with pressure fluid from a common hydraulic reservoir which is pressurized with just the one pump.

Soon to be two pumps.
You wonder why they didn't consider this previously, but they were a part way through grasshopper landing test when they realized that they needed grid fins.

Makes me wonder how well the " fins" on the New Glenn booster will work out for BO, or if they will have to iterate the design.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/09/2018 02:14 pm
What if the hydraulic pump stalls during the final main engine relight? Especially during the transition of the landing point so it can't stabilise to stop lateral movement?

Which of course is an unfair question because we don't know what caused it or what the stage's reaction to it would be so I can use the hydraulics as "magical failure turning this into dangerous hypothetical that probably never happens".

But when their secret billion dollar projects are on the line the Air Force can probably be pretty unfair, too.
We in the current generation, the engine was able to recover a wildly spinning ship and still land.

So the answer to your question is that if the fins failed after relight, the stage will land at the pad.  The fins are relatively ineffective at that point.

But you may as well alao ask what if the engine failed after relight...  To which the old aviation joke applies: "well sir, in that case, I guarantee you that we won't stay in the air forever".



-----
ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kdhilliard on 12/09/2018 03:35 pm
I only see 3 grid fins.
I think the fourth one is still there, just hidden behind the blue cradle that the booster is resting on.
Thanks to guckyfan for pointing me to some Ken Kremer tweets (1 (https://tinyurl.com/y8g3vcd8), 2 (https://tinyurl.com/y7jkf6rt)) with photos accounting for all four grid fins.

Edited to add: Not that we all haven't seen photos of the top three fins (that second photo is for completeness), but all the other photos of the stage on shore that I've seen only hinted at the possibility of a grid fin hiding behind that blue support structure.  This is the first one that makes it clear.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/09/2018 05:56 pm
Some component didn't work as it should have, and it wasn't noticed until that component was needed in flight.

Obviously adding redundancy might help. But if an investigation comes to the conclusion that overlooking something in assembly or during test procedures contributed to a faulty part ending up on an operational flight, this might end up with suggestions for operational, test or QC procedure changes that have implications for other flight hardware, relevant to commercial and possibly crewed launches too.

Suggestion: Do a test flight before using a booster for launches that count.  That's the way I think they do it in the airplane world.

Now shifting a bit... There's currently only one hydraulic pump because recovery isn't mission critical.  And the leading candidate change from this is to add a redundant pump.  But you also lack redundancy in the center engine during the recovery burns.  Just staying with pumps there's only one turbopump, one thrust vectoring hydraulic pump (or is it electric motor (doesn't matter)) and one of just about everything else on the engine.  Are you going to double those up now that recovery is a proven real part of flying F9?

Which brings me to... We've seen 3 engine landings, we've seen in this flight that roll control authority can be a challenge in some off script scenarios, we know that its not only the center engine but two additional ones (the ones which are used for re-entry burn) that have an enhanced TEA/TEB capacity and re-startability... I think this leads them to want to write some more software to allow F9 to make a choice to go to a 2 engine (the 2 outboard engines from the re-entry burn) landing burn in some off nominal situations such as the landing we had here.  Perhaps 2 engines could have controlled the roll early and allowed an early decision to go for a normal landing.?.

...Or not as a 2 engine landing burn would have been started at a much lower altitude thus cutting off the option of diverting to the LZ.  Hmm, I can see that this would work beneficially for an ASDS landing where the water impact point is probably much closer to the intended LZ (as evidenced by FH core's impact close to the ASDS) but maybe not so useful in an RTLS scenario where more horizontal divert is needed.  Corollary thought - intentional 3 engine burns are unlikely to be planned for RTLS not only because ASDS is the way to go in propellant challenged recoveries but also because 2 or 3 engine landings significantly reduce the distance between default impact point and intended LZ.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jak Kennedy on 12/09/2018 06:58 pm
 2 hydraulic pumps seems the simplest option but perhaps an accumulator or electric servos would be useful even with 1 or 2 pumps to give enough control to return the grid fins to a neutral position instead of them locking in a hard over position.

Edit, spelling
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: AJW on 12/10/2018 12:43 am
Through many decades of hard lessons, modern aircraft use both multiple actuators on each control surface as well as multiple independent hydraulic systems.  In commercial it is common to have at least three hydraulic systems using even different power sources.  As an example, Captain ‘Sully’s decision to start the APU early was considered critical in keeping his aircraft flying.   There are additional best practices for areas such as hydraulic line routing that need to be followed, so a single event is less likely to sever multiple controls. (UA232)

I think it has been an error to not have used redundant hydraulics, a standard that was used even on the Saturn V guidance and control system.   The CRS-16 control failure was just a matter of time and with landings moved out of the 'experimental' stage, I won't be surprised if RTLS is stopped until this single point of failure is properly addressed.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: LouScheffer on 12/10/2018 02:28 am
I think it has been an error to not have used redundant hydraulics, a standard that was used even on the Saturn V guidance and control system.   The CRS-16 control failure was just a matter of time and with landings moved out of the 'experimental' stage, I won't be surprised if RTLS is stopped until this single point of failure is properly addressed.
It's clear they need to do something.  A 1 in 30 chance of losing a $10m booster costs them $300k each time on the average.  But it's not obvious to me the best thing to do is make it redundant.  If instead they can make it 100x more reliable, then the cost of $3K would likely be less than redundant pumps, lines, tests, etc.  And since it only runs for 8 minutes at a time, finding or creating a pump that fails less than once per 8 minutes x 3000 missions = 24,000 minutes = every 17 days, does not seem to be impossible.  Lots of other hydraulics are more reliable than that.

Obviously, I don't have the detailed data to say whether a redundant pump, or a better pump, is the right solution.  I'm just pointing out that low cost is the goal, not reliability per se, and the more reliable system may not be the cheapest overall.
Title: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/10/2018 03:13 am
I think it has been an error to not have used redundant hydraulics, a standard that was used even on the Saturn V guidance and control system.   The CRS-16 control failure was just a matter of time and with landings moved out of the 'experimental' stage, I won't be surprised if RTLS is stopped until this single point of failure is properly addressed.

The landings are clearly not out of the experimental stage. You seem to not acknowledge the difference between flight critical systems (that are redundant) to landing systems (some which are not).

Did I miss Saturn V landings that exhibited redundant landing systems?

As for RTLS being stopped, I wouldn’t bet on it. Odds are SpaceX might address it before it would become an issue anyways.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: niwax on 12/10/2018 09:38 am
I think it has been an error to not have used redundant hydraulics, a standard that was used even on the Saturn V guidance and control system.   The CRS-16 control failure was just a matter of time and with landings moved out of the 'experimental' stage, I won't be surprised if RTLS is stopped until this single point of failure is properly addressed.

The landings are clearly not out of the experimental stage. You seem to not acknowledge the difference between flight critical systems (that are redundant) to landing systems (some which are not).

That's exactly the point. They have missions that are just light enough to be landed - FH center core and that heavy GTO record for example. Adding extra mass for non mission-critical items that pushes these launches to expendable boosters is not an effective solution. Maybe there are completely different solutions such as an improved hydraulic system combined with some sort of insurance - their landing record is now as good as some of the best launchers.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jcc on 12/10/2018 11:18 am
What I would like to know is how precisely did the stage hit the water target. It seems pretty clear that if it had landed on a hard surface it would have landed upright, so could it have landed on the ASDS?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: vanoord on 12/10/2018 11:43 am
The landings are clearly not out of the experimental stage. You seem to not acknowledge the difference between flight critical systems (that are redundant) to landing systems (some which are not).

Did I miss Saturn V landings that exhibited redundant landing systems?

As for RTLS being stopped, I wouldn’t bet on it. Odds are SpaceX might address it before it would become an issue anyways.

While landings are no longer described as 'experimental' on the SpaceX webcasts, as far as I can recall there was always an expectation that some cores would be lost on landing.

The current success rate for landings is around 82% overall and 89% for Block 5.

If they lose 1 in 10 over the next couple of years, that shouldn't be too surprising.

Over time that figure is likely to come down as new issues are discovered, dealt with and the landing process refined.

Landing the booster(s) is not the primary mission objective, but has been a useful bonus which has turned into an important part of the business - and there's no reason to halt attempts just because one booster has made a contingency landing at sea.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Zed_Noir on 12/10/2018 12:21 pm
What I would like to know is how precisely did the stage hit the water target. It seems pretty clear that if it had landed on a hard surface it would have landed upright, so could it have landed on the ASDS?

Since SpaceX only have the OCISLY ASDS available on the East Coast now. The ASDS have to be available and not transporting another recovered core at the time or laid up at dock for maintenance.

Consideration also have to be given to how much priority the future cores being recovered might be. Giving redundant landing opportunity to a RTLS core might cost you the availability of the ASDS until you disembarked the landed core and refitted the ASDS. So you might want to spend more effect on recovering newer cores and less on older cores.

IMO SpaceX needs at least 2 ASDS if they want at least one available for down range recovery operations every 2 weeks or so. Without even accounting for unscheduled downtime for any of the ASDS.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: edzieba on 12/10/2018 01:44 pm
What I would like to know is how precisely did the stage hit the water target. It seems pretty clear that if it had landed on a hard surface it would have landed upright, so could it have landed on the ASDS?
From the tracking video, the stage had a decent amount of angle and sideslip on 'land'ing. We've seen that combination in the past with CRS-6, and it did not end well for the stage.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/10/2018 03:22 pm
What I would like to know is how precisely did the stage hit the water target. It seems pretty clear that if it had landed on a hard surface it would have landed upright, so could it have landed on the ASDS?
From the tracking video, the stage had a decent amount of angle and sideslip on 'land'ing. We've seen that combination in the past with CRS-6, and it did not end well for the stage.
If I had to perform a cross-controlled water landing in ocean swells I doubt I would have fared better... ;D
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: SimonFD on 12/10/2018 03:27 pm
What I would like to know is how precisely did the stage hit the water target. It seems pretty clear that if it had landed on a hard surface it would have landed upright, so could it have landed on the ASDS?
From the tracking video, the stage had a decent amount of angle and sideslip on 'land'ing. We've seen that combination in the past with CRS-6, and it did not end well for the stage.

Yes, late on in the descent it seemed to be attempting a landing on a specific bit of water rather than the water directly below it.
I suspect some extra code along the lines of "if we're not landing on land, don't bother veering off 10 feet to the left, 50 feet off the water" will be added.
Of course, it could have been a gust of wind which triggered the "correct for wind" algorithm. The above still applies though.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/10/2018 03:44 pm
the engine was able to recover a wildly spinning ship .


Not that incorrect statement again
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/10/2018 03:45 pm
What I would like to know is how precisely did the stage hit the water target. It seems pretty clear that if it had landed on a hard surface it would have landed upright, so could it have landed on the ASDS?
From the tracking video, the stage had a decent amount of angle and sideslip on 'land'ing. We've seen that combination in the past with CRS-6, and it did not end well for the stage.

Yes, late on in the descent it seemed to be attempting a landing on a specific bit of water rather than the water directly below it.
I suspect some extra code along the lines of "if we're not landing on land, don't bother veering off 10 feet to the left, 50 feet off the water" will be added.
Of course, it could have been a gust of wind which triggered the "correct for wind" algorithm. The above still applies though.
I'm sure they will look at all the data and contingency. Let's not forget that the stage would be coping with wind shear at different altitudes while rapidly descending through them...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/10/2018 03:49 pm
What I would like to know is how precisely did the stage hit the water target. It seems pretty clear that if it had landed on a hard surface it would have landed upright, so could it have landed on the ASDS?
From the tracking video, the stage had a decent amount of angle and sideslip on 'land'ing. We've seen that combination in the past with CRS-6, and it did not end well for the stage.

Yes, late on in the descent it seemed to be attempting a landing on a specific bit of water rather than the water directly below it.
I suspect some extra code along the lines of "if we're not landing on land, don't bother veering off 10 feet to the left, 50 feet off the water" will be added.
Of course, it could have been a gust of wind which triggered the "correct for wind" algorithm. The above still applies though.
I'm sure they will look at all the data and contingency. Let's not forget that the stage would be coping with wind shear at different altitudes while rapidly descending through them...
Yup, but the tilt at about 5 seconds before touchdown looked like a very deliberate counter-wind maneuver.


IIRC it was windy during launch, and touchdown was with very little horizontal speed.

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ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/10/2018 03:55 pm
What I would like to know is how precisely did the stage hit the water target. It seems pretty clear that if it had landed on a hard surface it would have landed upright, so could it have landed on the ASDS?
From the tracking video, the stage had a decent amount of angle and sideslip on 'land'ing. We've seen that combination in the past with CRS-6, and it did not end well for the stage.

Yes, late on in the descent it seemed to be attempting a landing on a specific bit of water rather than the water directly below it.
I suspect some extra code along the lines of "if we're not landing on land, don't bother veering off 10 feet to the left, 50 feet off the water" will be added.
Of course, it could have been a gust of wind which triggered the "correct for wind" algorithm. The above still applies though.
I'm sure they will look at all the data and contingency. Let's not forget that the stage would be coping with wind shear at different altitudes while rapidly descending through them...
Yup, but the tilt at about 5 seconds before touchdown looked like a very deliberate counter-wind maneuver.


IIRC it was windy during launch, and touchdown was with very little horizontal speed.

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ABCD: Always Be Counting Down
Like I said they will look at "all the data"...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: edzieba on 12/10/2018 03:55 pm
the engine was able to recover a wildly spinning ship .


Not that incorrect statement again
For the record (using 'rotation about the Y axis' as 'Roll' as 'rotation about the stage's long axis' convention):

- A centre mounted engine can do nothing about spin purely about the rocket's own Y axis.
- A centre mounted engine can arrest rotation about an axis perpendicular to the Earth's surface (i.e. Y in world coodrinates) provided the stage's own Y axis is not aligned to this axis
- The amount of world-coord-Y-rotation the engine can arrest is proportional to the angle between the stage-centric Y axis and the world-centric Y axis (i.e. Sin(offset)). 0% at 0° offset, 100% at 90° offset or the stage perpendicular to the ground.
- Or alternatively, the inverse of the offset (Cos(offset)) is the residual 'spin' the engine will be unable to arrest.
- Given sufficient time (which a stage hurtling towards unscheduled Lithobraking does not have) atmospheric coupling can be used to convert stage-centric-Y roll to world-centric-Y roll, which the engine would then be able to arrest.

tl;dr: how much 'spin' a centre-mounted engine can arrest depends on what your specific definition of spin is, and how much time you have between atmospheric entry and "Oh no, not again".
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/10/2018 04:06 pm
the engine was able to recover a wildly spinning ship .


Not that incorrect statement again
For the record (using 'rotation about the Y axis' as 'Roll' as 'rotation about the stage's long axis' convention):

- A centre mounted engine can do nothing about spin purely about the rocket's own Y axis.
- A centre mounted engine can arrest rotation about an axis perpendicular to the Earth's surface (i.e. Y in world coodrinates) provided the stage's own Y axis is not aligned to this axis
- The amount of world-coord-Y-rotation the engine can arrest is proportional to the angle between the stage-centric Y axis and the world-centric Y axis. 0% at 0° offset, 100% at 90° offset (i.e. Sin(offset)), or the stage perpendicular to the ground.
- Or alternatively, the inverse of the offset (Cos(offset)) is the residual 'spin' the engine will be unable to arrest.
- Given sufficient time (which a stage hurtling towards unscheduled Lithobraking does not have) atmospheric coupling can be used to convert stage-centric-Y roll to world-centric-Y roll, which the engine would then be able to arrest.

tl;dr: how much 'spin' a centre-mounted engine can arrest depends on what your specific definition of spin is, and how much time you have between atmospheric entry and "Oh no, not again".
It's pretty simple...  The effect of leg extension is easy to calculate and it will simply reduce the rate of rotation by the ratio of moments of inertia, before and after deployment.  It cannot null the rotation.

But somebody clearly did, and it wasn't the fins.

So this leaves the engine.  The majority of the work done by the engine was to righten the stage (as would be the priority of the control system) but as it did so, the moment of inertia of the stage clearly decreased - so why didn't speed of rotation increase?  (Skater analogy again)

The reason was, again, because the control system was actively taking spin about the Z axis out of the system.



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ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/10/2018 04:11 pm
For conventions sake: Would apply to the entire stack including booster return.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: edzieba on 12/10/2018 04:15 pm
I was only talking about the engine's contribution specifically. In addition, there will be drag from the fins (actuated or not), drag from the legs (extended or retracted, they protrude from the stage), moment of inertia change from leg extension, drag from the stage itself (skin drag), drag from the stage body being not perfectly aligned to the world-centric axis of spin, the actions of the cold-gas thrusters, and the reduction in induced spin from the offset fin as the stage slowed.

No one factor is "the reason" the stage was able to (just about) arrest the induced rotation. Only some of these factors would be ones the stage's GNC could potentially control, and it is likely that only the cold-gas thrusters were ones it was actively attempting to use to arrest the spin, with the aerodynamic effects and the engine being offset likely being coincidental help rather than deliberate action (though I wouldn't put it past SpaceX to make them deliberate actions eventually, as with the 'if the stage blows up, deploy the chutes' logic for Dragon after CRS-7).
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Kansan52 on 12/10/2018 04:27 pm
Part of the investigation will be "How did we do that!?". That landing recovery seemed doomed when the control problems began.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/10/2018 04:54 pm
Part of the investigation will be "How did we do that!?". That landing recovery seemed doomed when the control problems began.
Just to play "devil's advocate" for a second... How do we know the did not try this failure out in a sim? A great question for Chris to ask... ;)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: hootowls on 12/10/2018 04:54 pm
Well, they didn't let them do an RTLS at Vandenberg earlier this week in case something happens, I wonder how the Air Force looks at that decision after this failure.

On the one hand if the exact same failure happens, seems like there's no danger to Vandenberg at all, the stage just lands in the Pacific (that recovery would be worse though, seeing as the West Coast SpaceX fleet is based further away than "just pop down the road"-Cape Canaveral).

On the other hand, if something happens a couple of minutes later during the landing burn or something else just doesn't work in general...sure shows there'll always be some danger to this whole thing.

Actually now that I think about it, having your landing site be directly next to your launch pad is probably convenient but if something goes wrong...especially at your only West Coast pad compared to the two Florida pads you have...well, I hope all their failures end as smoothly and entertainingly as this one.
We know the answer to your first question.

The stage doesn't shift the IIP onto shore until the main engine relight happens and the engine is confirmed good.

We can also assume that any other health checks that fail also result in an offshore landing.

They can also walk the IIP along a safe corridor as it approaches the landing pad.  There's no reason that the post-relight path must be collinear with the pre-relight path.

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ABCD: Always Be Counting Down



The IIP shift to land logic is not univesally true - look at the SAOCOM-1A mission.
Title: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Johnnyhinbos on 12/10/2018 05:01 pm
the engine was able to recover a wildly spinning ship .


Not that incorrect statement again
What I can’t conceive of is how there was any kind of control authority with the landing burn. The stage is rotating - the center engine is gimbaling to balance the booster during descent, but the rotation the changes the relative angle of thrust so the control algorithm has to gimbal in a new angle, but the booster rotates, so it has to gimbal again to correct, but the booster rotates... you get the idea. This looks like it would quickly lead to a runaway instability situation as the mechanical actuators fall behind the control inputs. How they kept that thing under control is pretty impressive.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/10/2018 05:04 pm
the engine was able to recover a wildly spinning ship .


Not that incorrect statement again
What I can’t conceive of is how there was any kind of control authority with the landing burn. The stage is rotating - the center engine is gimbaling to balance the booster during descent, but the rotation the changes the relative angle of thrust so the control algorithm has to gimbal in a new angle, but the booster rotates, so it has to gimbal again to correct, but the booster rotates... you get the idea. This looks like it would quickly lead to a runaway instability situation as the mechanical actuators fall behind the control inputs. How they kept that thing under control is pretty impressive.
Computers, man.  They're the future!

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ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/10/2018 05:09 pm
the engine was able to recover a wildly spinning ship .


Not that incorrect statement again
What I can’t conceive of is how there was any kind of control authority with the landing burn. The stage is rotating - the center engine is gimbaling to balance the booster during descent, but the rotation the changes the relative angle of thrust so the control algorithm has to gimbal in a new angle, but the booster rotates, so it has to gimbal again to correct, but the booster rotates... you get the idea. This looks like it would quickly lead to a runaway instability situation as the mechanical actuators fall behind the control inputs. How they kept that thing under control is pretty impressive.

The RCS thrusters.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/10/2018 05:14 pm
the engine was able to recover a wildly spinning ship .


Not that incorrect statement again
What I can’t conceive of is how there was any kind of control authority with the landing burn. The stage is rotating - the center engine is gimbaling to balance the booster during descent, but the rotation the changes the relative angle of thrust so the control algorithm has to gimbal in a new angle, but the booster rotates, so it has to gimbal again to correct, but the booster rotates... you get the idea. This looks like it would quickly lead to a runaway instability situation as the mechanical actuators fall behind the control inputs. How they kept that thing under control is pretty impressive.

The RCS thrusters.
True, but I don't think they do much compared to what the fins are doing, and they have limited stored impulse. They're mostly for use in vacuum when disturbing forces are low.  (Hence the grid fins)


 Can calculate though...  Later today...

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ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Kabloona on 12/10/2018 05:16 pm
the engine was able to recover a wildly spinning ship .


Not that incorrect statement again
What I can’t conceive of is how there was any kind of control authority with the landing burn. The stage is rotating - the center engine is gimbaling to balance the booster during descent, but the rotation the changes the relative angle of thrust so the control algorithm has to gimbal in a new angle, but the booster rotates, so it has to gimbal again to correct, but the booster rotates... you get the idea. This looks like it would quickly lead to a runaway instability situation as the mechanical actuators fall behind the control inputs. How they kept that thing under control is pretty impressive.

The RCS thrusters.

Yes, if you watch Scott Manley's commentary video, he observes that towards the end of the landing burn, as the stage slows, the grid fins exert less roll torque on the stage, and the RCS thrusters manage to null the roll, and even over-correct to the point that you can see an RCS thruster firing to counter the over-correction.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Kabloona on 12/10/2018 05:18 pm
[

The RCS thrusters.
True, but I don't think they do much compared to what the fins are doing, and they have limited stored impulse. They're mostly for use in vacuum when disturbing forces are low.  (Hence the grid fins)


 Can calculate though...  Later today...

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ABCD: Always Be Counting Down

See above post. Watch Scott Manley's video. You can see the RCS thrusters gaining control of the roll in the last few seconds as the stage slows and the grid fins lose their mojo. The thrusters even manage to over-correct, then fire one last burst in the opposite direction to null the over-correction.

See at about 4:30 into the video.

https://www.youtube.com/watch?v=EH1nyPIvLjI
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/10/2018 05:20 pm
the engine was able to recover a wildly spinning ship .


Not that incorrect statement again
What I can’t conceive of is how there was any kind of control authority with the landing burn. The stage is rotating - the center engine is gimbaling to balance the booster during descent, but the rotation the changes the relative angle of thrust so the control algorithm has to gimbal in a new angle, but the booster rotates, so it has to gimbal again to correct, but the booster rotates... you get the idea. This looks like it would quickly lead to a runaway instability situation as the mechanical actuators fall behind the control inputs. How they kept that thing under control is pretty impressive.

The RCS thrusters.

Yes, if you watch Scott Manley's commentary video, he observes that towards the end of the landing burn, as the stage slows, the grid fins exert less roll torque on the stage, and the RCS thrusters manage to null the roll, and even over-correct to the point that you can see an RCS thruster firing to counter the over-correction.

I think Scott misinterpreted the last part... The RCS never completely cancelled out the rotation completely. The last switch in RCS thruster direction was to prevent the booster from falling over.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: rocketguy101 on 12/10/2018 05:23 pm
For conventions sake: Would apply to the entire stack including booster return.

From the horse's mouth...https://www.spacex.com/sites/spacex/files/falcon_9_users_guide_rev_2.0.pdf (https://www.spacex.com/sites/spacex/files/falcon_9_users_guide_rev_2.0.pdf)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/10/2018 05:24 pm
Here's are some quick numbers for the legs.

The stage weighs 25 tons empty.  good approx. Is that the mass is at 1.7 m radius.  MR2 = 72.25

After leg deploy, 2 tons moved out about 2.5 m (based on c.g. of the legs being about 1/3 of the way out) so now

23 tons at 1.7 m and 2 tons at 4.2 m = 66.5+35.3 = 112.

So the ratio of moments of inertia is 112/75 = 1.5. 

That's all there is.  I ball-parked it at 2.0 previously.

So leg deployment reduces the rate of rotation by 1.5x or maybe 2.0x if I got the c.g. a little bit wrong.

I'll see what the RCS can do later on, but I want to watch the video again to see if they were on after leg deployment.

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Kabloona on 12/10/2018 05:27 pm

I'll see what the RCS can do later on, but I want to watch the video again to see if they were on after leg deployment.

Yes, they were. Again, watch the video above. You can see around 4:30 one of the RCS thrusters is on almost coninuously to counter the roll just before splashdown.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Kabloona on 12/10/2018 05:28 pm
the engine was able to recover a wildly spinning ship .


Not that incorrect statement again
What I can’t conceive of is how there was any kind of control authority with the landing burn. The stage is rotating - the center engine is gimbaling to balance the booster during descent, but the rotation the changes the relative angle of thrust so the control algorithm has to gimbal in a new angle, but the booster rotates, so it has to gimbal again to correct, but the booster rotates... you get the idea. This looks like it would quickly lead to a runaway instability situation as the mechanical actuators fall behind the control inputs. How they kept that thing under control is pretty impressive.

The RCS thrusters.

Yes, if you watch Scott Manley's commentary video, he observes that towards the end of the landing burn, as the stage slows, the grid fins exert less roll torque on the stage, and the RCS thrusters manage to null the roll, and even over-correct to the point that you can see an RCS thruster firing to counter the over-correction.

I think Scott misinterpreted the last part... The RCS never completely cancelled out the rotation completely. The last switch in RCS thruster direction was to prevent the booster from falling over.

That's a good point about trying to stay upright vs. countering the roll, but it does look to me like the RCS nulled the rate pretty close to zero by touchdown.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/10/2018 05:29 pm
For conventions sake: Would apply to the entire stack including booster return.

From the horse's mouth...https://www.spacex.com/sites/spacex/files/falcon_9_users_guide_rev_2.0.pdf (https://www.spacex.com/sites/spacex/files/falcon_9_users_guide_rev_2.0.pdf)
Standard coordinate conventions... :)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Kabloona on 12/10/2018 05:38 pm
This also begs the question of how F9 managed not to run out of GN2 for the RCS thrusters. From the video it's evident that the thrusters are only intermittently trying to counter the roll, not thrusting continuously, so there must be some control logic that is designed to conserve GN2 even in the case of a hard-over grid fin.

Maybe someone thought through failure scenarios enough to realize that, in the case of a stuck grid fin causing roll, the grid fins would eventually lose aerodynamic control authority just before landing, and the RCS thrusters would be able to recover as long as they had enough GN2 left.

In which case the priority becomes conserving GN2 on the way down vs. blowing it all out trying futilely to counter the grid fins.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/10/2018 05:46 pm
This also begs the question of how F9 managed not to run out of GN2 for the RCS thrusters. From the video it's evident that the thrusters are not "full on" all the time trying to counter the roll, so there must be some control logic that is designed to conserve GN2 even in the case of a hard-over grid fin.

Maybe someone thought through failure scenarios enough to realize that, in the case of a stuck grid fin causing roll, the grid fins would eventually lose aerodynamic control authority just before landing, and the RCS thrusters would be able to recover as long as they had enough GN2 left.

In which case the priority becomes conserving GN2 on the way down vs. blowing it all out trying futilely to counter the grid fins.
Throw in the conservation of angular momentum with leg extension and you're golden... ;)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/10/2018 05:47 pm
This also begs the question of how F9 managed not to run out of GN2 for the RCS thrusters. From the video it's evident that the thrusters are only intermittently trying to counter the roll, not thrusting continuously, so there must be some control logic that is designed to conserve GN2 even in the case of a hard-over grid fin.

Maybe someone thought through failure scenarios enough to realize that, in the case of a stuck grid fin causing roll, the grid fins would eventually lose aerodynamic control authority just before landing, and the RCS thrusters would be able to recover as long as they had enough GN2 left.

In which case the priority becomes conserving GN2 on the way down vs. blowing it all out trying futilely to counter the grid fins.

Grid fins have superior control authority for the vast majority of the descent through the atmosphere. The RCS thrusters would only be useful when the grid fins can't control the booster, which would be prior to reentry and in the last couple seconds before touchdown.

Would be simple to program the booster to not bother to use RCS at all until it is useful, rather than for a failure.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/10/2018 06:03 pm
Don't underestimate the torque being imparted in the final moments during the rotating leg extension through the CoG...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Kabloona on 12/10/2018 06:16 pm
This also begs the question of how F9 managed not to run out of GN2 for the RCS thrusters. From the video it's evident that the thrusters are only intermittently trying to counter the roll, not thrusting continuously, so there must be some control logic that is designed to conserve GN2 even in the case of a hard-over grid fin.

Maybe someone thought through failure scenarios enough to realize that, in the case of a stuck grid fin causing roll, the grid fins would eventually lose aerodynamic control authority just before landing, and the RCS thrusters would be able to recover as long as they had enough GN2 left.

In which case the priority becomes conserving GN2 on the way down vs. blowing it all out trying futilely to counter the grid fins.

Grid fins have superior control authority for the vast majority of the descent through the atmosphere. The RCS thrusters would only be useful when the grid fins can't control the booster, which would be prior to reentry and in the last couple seconds before touchdown.

Would be simple to program the booster to not bother to use RCS at all until it is useful, rather than for a failure.

It does appear in the video that the RCS is inhibited until just before the landing burn. Then the RCS thrusters come on intermittently trying to null the roll. But even then, they're not on continuously. The one visible in the camera field of view operates only intermittently, until just before splashdown when it fires for several seconds in a last, apparently successful, attempt to stop the roll.

So yes, it does make sense to inhibit RCS most of the way down, but even when the RCS is re-enabled and tried to stop the roll, the thrusters aren't running continuously.

Which intermittence is either control logic whose purpose escapes me, or possible conservation logic to preserve GN2.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/10/2018 06:19 pm

So this leaves the engine. 


Wrong, there is the RCS.  Which does roll control on single engine burns above the atmosphere and during slow speeds in the atmosphere.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Pete on 12/10/2018 06:20 pm

What I can’t conceive of is how there was any kind of control authority with the landing burn. The stage is rotating - the center engine is gimbaling to balance the booster during descent, but the rotation the changes the relative angle of thrust so the control algorithm has to gimbal in a new angle, but the booster rotates, so it has to gimbal again to correct, but the booster rotates... you get the idea. This looks like it would quickly lead to a runaway instability situation as the mechanical actuators fall behind the control inputs. How they kept that thing under control is pretty impressive.

Obviously, the reaction time for the engine gimbal is quicker than the rate of change imparted by that spin.
Which, yes, means that is one ridiculously nimble engine!
I expect they did this to make the propulsive landing possible in the first place, you do not want a large actuator lag for gimbal control on top of all the other control delays in the last few milliseconds of a landing.

Does anyone here have actual info on the max gimbal speed/rate of the center engine? For example, from first command to position achieved, how long for the engine to gimbal 4 degrees?
For that matter, just what is the maximum deflection achievable on that engine?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/10/2018 06:22 pm

So this leaves the engine. 


Wrong, there is the RCS.  Which does roll control on single engine burns above the atmosphere and during slow speeds in the atmosphere.
I'll look into the RCS later, but are we at least done saying the leg extension did it?

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ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/10/2018 06:34 pm

So this leaves the engine. 


Wrong, there is the RCS.  Which does roll control on single engine burns above the atmosphere and during slow speeds in the atmosphere.
I'll look into the RCS later, but are we at least done saying the leg extension did it?


No,  Read the original post.

https://forum.nasaspaceflight.com/index.php?topic=45881.msg1884475#msg1884475
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/10/2018 07:08 pm

So this leaves the engine. 


Wrong, there is the RCS.  Which does roll control on single engine burns above the atmosphere and during slow speeds in the atmosphere.
I'll look into the RCS later, but are we at least done saying the leg extension did it?


No,  Read the original post.

https://forum.nasaspaceflight.com/index.php?topic=45881.msg1884475#msg1884475

No.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Cinder on 12/10/2018 07:50 pm
What I would like to know is how precisely did the stage hit the water target. It seems pretty clear that if it had landed on a hard surface it would have landed upright, so could it have landed on the ASDS?
The stage looked like it was busier staying vertical than aiming for an area the size of an ASDS, so it'd've'd to be something larger like some vacant lot of land.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: marsbase on 12/10/2018 08:56 pm
What I would like to know is how precisely did the stage hit the water target. It seems pretty clear that if it had landed on a hard surface it would have landed upright, so could it have landed on the ASDS?
The stage looked like it was busier staying vertical than aiming for an area the size of an ASDS, so it'd've'd to be something larger like some vacant lot of land.
The center core of the FH Demo did real damage to OCISLY so maybe it's not a good idea to aim a malfunctioning rocket at an expensive vessel.  I suspect this booster could have landed at LZ1 if given the chance, but of course that is not possible.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Joffan on 12/10/2018 10:02 pm
What I would like to know is how precisely did the stage hit the water target. It seems pretty clear that if it had landed on a hard surface it would have landed upright, so could it have landed on the ASDS?
The stage looked like it was busier staying vertical than aiming for an area the size of an ASDS, so it'd've'd to be something larger like some vacant lot of land.
The center core of the FH Demo did real damage to OCISLY so maybe it's not a good idea to aim a malfunctioning rocket at an expensive vessel.  I suspect this booster could have landed at LZ1 if given the chance, but of course that is not possible.
I strongly doubt this booster could have realigned itself to the pad. It just managed to beat the spin right at the end but it couldn't have translated the target point during the spin with any great control.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/10/2018 10:56 pm
the engine was able to recover a wildly spinning ship .


Not that incorrect statement again
What I can’t conceive of is how there was any kind of control authority with the landing burn. The stage is rotating - the center engine is gimbaling to balance the booster during descent, but the rotation the changes the relative angle of thrust so the control algorithm has to gimbal in a new angle, but the booster rotates, so it has to gimbal again to correct, but the booster rotates... you get the idea. This looks like it would quickly lead to a runaway instability situation as the mechanical actuators fall behind the control inputs. How they kept that thing under control is pretty impressive.

The answer to that is "feed forward control". In a nutshell, the computer knows how quick the TVC gimbal can possibly respond. As such they don't "chase" the control loop by moving the TVC where it would have to be now to fix the current situation (atitude, rotation speed) but to the orientation it needs to be in a short time in the future if the system keeps transitioning based on physics (inertia, current control output)

with some control algorithms (model predictive control for example) the computer simulates the behavior of the entire system a few seconds into the future and tries to find the sequence of control outputs that leads to the best possible output.

if its really good, it even "knows" (based on sensors, hydraulic pressure, or inherent system analysis based one expected and actual outcome) that the grid fins aren't doing their job and altered the model based on observed behavior as opposed to a hardcoded model.

you can do that kind of thing arbitrarily complex, but at some point it becomes too computationally expensive, so you take shortcuts with lookup tables based on values you expect not to change (like system geometry and resulting aerodynamic forces) so obviously there's a point when even that sophisticated system can't cope.

but that SpaceX is doing more than just a simple PID controller, I think this landing demonstrated quite impressively :-)

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: marsbase on 12/10/2018 11:05 pm
What I would like to know is how precisely did the stage hit the water target. It seems pretty clear that if it had landed on a hard surface it would have landed upright, so could it have landed on the ASDS?
The stage looked like it was busier staying vertical than aiming for an area the size of an ASDS, so it'd've'd to be something larger like some vacant lot of land.
The center core of the FH Demo did real damage to OCISLY so maybe it's not a good idea to aim a malfunctioning rocket at an expensive vessel.  I suspect this booster could have landed at LZ1 if given the chance, but of course that is not possible.
I strongly doubt this booster could have realigned itself to the pad. It just managed to beat the spin right at the end but it couldn't have translated the target point during the spin with any great control.
Yes, I think you're right. The grid fins play a major role in translation as I understand it.  I just meant that if the guidance had targeted LZ1 from the beginning the booster, which was almost vertical and not rotating much at touchdown ,might have remained standing on the pad. 
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/10/2018 11:54 pm
What I would like to know is how precisely did the stage hit the water target. It seems pretty clear that if it had landed on a hard surface it would have landed upright, so could it have landed on the ASDS?
The stage looked like it was busier staying vertical than aiming for an area the size of an ASDS, so it'd've'd to be something larger like some vacant lot of land.
The center core of the FH Demo did real damage to OCISLY so maybe it's not a good idea to aim a malfunctioning rocket at an expensive vessel.  I suspect this booster could have landed at LZ1 if given the chance, but of course that is not possible.
I strongly doubt this booster could have realigned itself to the pad. It just managed to beat the spin right at the end but it couldn't have translated the target point during the spin with any great control.
Yes, I think you're right. The grid fins play a major role in translation as I understand it.  I just meant that if the guidance had targeted LZ1 from the beginning the booster, which was almost vertical and not rotating much at touchdown ,might have remained standing on the pad.
Remember grasshopper? 

I'm pretty sure the translation from ocean to pad occurs (gently) over the course of the landing burn, principally by the engine.

The fins control the booster mainly between the burns.


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ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: georgegassaway on 12/11/2018 01:16 am
Remember grasshopper? 

I'm pretty sure the translation from ocean to pad occurs (gently) over the course of the landing burn, principally by the engine.

The fins control the booster mainly between the burns.

I remember Grasshopper. The translation it did was maybe 200-300 feet. Not several MILES.

The F9 re-entry is very steep, nearly vertical, ballistically falling towards a spot a few miles out from shore.

After reentry burn, the grid fins aerodynamically steer it in a steep diagonal dogleg path towards the landing zone (the translational distance from ballistic path in the ocean towards to the LZ).

By the time that the landing burn begins , the translation begins to slow and the path begins to curve from a steep diagonal dogleg towards vertical. In other words, there is LESS translation once the landing burn begins, not more. And the grid fins are still helping with the steering during that time. Indeed the first part of the landing burn the grid fins should still be dominant in steering.  When it gets slower, then the thrust vectoring has more of an effect in steering than the grid fins do, more and more effective as it gets slower and slower.

Tim Dodd (Everyday Astronaut) posted a very good video which explains the landing process, with the grid fins steering the dogleg translation, among other things. Maybe it has already been posted in this thread, but apparently some have not seen it.

https://www.youtube.com/watch?v=_KAK64wtMe4

With the grid fin steering out, the best that the Falcon could do, was to land slowly somewhere, totally incapable of steering to a specific spot (especially with the rolling). And that somewhere was in the ocean as it was  too far out to make it to land (thank goodness). It was surprising it ended up as close as a half mile away from shore, that is far closer than was supposed to possible. I won’t be surprised if CCAFS investigates how it could get that close. Most likely that it did already start the aerodynamic translation for a short time before things went to hell, then once the grid fins went out the transition ended to become mostly ballistic again (albeit rolling, but averaging out any pitch/yaw effects from the stuck fins). But by then it had moved the ballistic path closer to the  coastline.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/11/2018 01:21 am
Remember grasshopper? 

I'm pretty sure the translation from ocean to pad occurs (gently) over the course of the landing burn, principally by the engine.

The fins control the booster mainly between the burns.

I remember Grasshopper. The translation it did was maybe 200-300 feet. Not several MILES.

The F9 re-entry is very steep, nearly vertical, ballistically falling towards a spot a few miles out from shore.

After reentry burn, the grid fins aerodynamically steer it in a steep diagonal dogleg path towards the landing zone (the translational distance from ballistic path in the ocean towards to the LZ).

By the time that the landing burn begins , the translation begins to slow and the path begins to curve from a steep diagonal dogleg towards vertical. In other words, there is LESS translation once the landing burn begins, not more. And the grid fins are still helping with the steering during that time. Indeed the first part of the landing burn the grid fins should still be dominant in steering.  When it gets slower, then the thrust vectoring has more of an effect in steering than the grid fins do, more and more effective as it gets slower and slower.

Tim Dodd (Everyday Astronaut) posted a very good video which explains the landing process, with the grid fins steering the dogleg translation, among other things. Maybe it has already been posted in this thread, but apparently some have not seen it.

https://www.youtube.com/watch?v=_KAK64wtMe4

With the grid fin steering out, the best that the Falcon could do, was to land slowly somewhere, totally incapable of steering to a specific spot (especially with the rolling). And that somewhere was in the ocean as it was  too far out to make it to land (thank goodness). It was surprising it ended up as close as a half mile away from shore, that is far closer than was supposed to possible. I won’t be surprised if CCAFS investigates how it could get that close. Most likely that it did already start the aerodynamic translation for a short time before things went to hell, then once the grid fins went out the transition ended to become mostly ballistic again (albeit rolling, but averaging out any pitch/yaw effects from the stuck fins). But by then it had moved the ballistic path closer to the  coastline.

The video states no roll control from single engine and leg deployment reducing roll.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/11/2018 01:43 am
Remember grasshopper? 

I'm pretty sure the translation from ocean to pad occurs (gently) over the course of the landing burn, principally by the engine.

The fins control the booster mainly between the burns.

I remember Grasshopper. The translation it did was maybe 200-300 feet. Not several MILES.

The F9 re-entry is very steep, nearly vertical, ballistically falling towards a spot a few miles out from shore.

After reentry burn, the grid fins aerodynamically steer it in a steep diagonal dogleg path towards the landing zone (the translational distance from ballistic path in the ocean towards to the LZ).

By the time that the landing burn begins , the translation begins to slow and the path begins to curve from a steep diagonal dogleg towards vertical. In other words, there is LESS translation once the landing burn begins, not more. And the grid fins are still helping with the steering during that time. Indeed the first part of the landing burn the grid fins should still be dominant in steering.  When it gets slower, then the thrust vectoring has more of an effect in steering than the grid fins do, more and more effective as it gets slower and slower.

Tim Dodd (Everyday Astronaut) posted a very good video which explains the landing process, with the grid fins steering the dogleg translation, among other things. Maybe it has already been posted in this thread, but apparently some have not seen it.

https://www.youtube.com/watch?v=_KAK64wtMe4

With the grid fin steering out, the best that the Falcon could do, was to land slowly somewhere, totally incapable of steering to a specific spot (especially with the rolling). And that somewhere was in the ocean as it was  too far out to make it to land (thank goodness). It was surprising it ended up as close as a half mile away from shore, that is far closer than was supposed to possible. I won’t be surprised if CCAFS investigates how it could get that close. Most likely that it did already start the aerodynamic translation for a short time before things went to hell, then once the grid fins went out the transition ended to become mostly ballistic again (albeit rolling, but averaging out any pitch/yaw effects from the stuck fins). But by then it had moved the ballistic path closer to the  coastline.

The video states no roll control from single engine and leg deployment reducing roll.
Whose video?  EDA's?  He's just a webcaster, and he uses Kerbal, and his simulated F9 does not have the real F9's control software, so of course he can't do fancy stuff like coupled rotational axes.

The man in charge, meanwhile, said it was the engine.

And nobody argued the legs reduce roll.  I even calculated it above.  Somewhere between 1.5, and 2.  Clearly a lot less then we saw in practice.

The fact is, roll decreased before the legs deployed.

How long was the RCS firing, comulatively?

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ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/11/2018 01:48 am
The man in charge, meanwhile, said it was the engine.

If you are going to quote the man in charge, don't mis-quote. engineS. (so ... including RCS)

https://twitter.com/elonmusk/status/1070399755526656000
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/11/2018 01:54 am
The man in charge, meanwhile, said it was the engine.

If you are going to quote the man in charge, don't mis-quote. engineS. (so ... including RCS)

https://twitter.com/elonmusk/status/1070399755526656000

OK fair enough, so RCS is fair play based on Musk's statement.  Also, unlike the leg deployment, RCS can indeed bring the roll to zero.

Let's figure out how much they did tho.  Based on the videos, how long IYO were the RCS firing?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Kabloona on 12/11/2018 02:23 am
The man in charge, meanwhile, said it was the engine.

If you are going to quote the man in charge, don't mis-quote. engineS. (so ... including RCS)

https://twitter.com/elonmusk/status/1070399755526656000

OK fair enough, so RCS is fair play based on Musk's statement.  Also, unlike the leg deployment, RCS can indeed bring the roll to zero.

Let's figure out how much they did tho.  Based on the videos, how long IYO were the RCS firing?

I get about 12 seconds of roll-correction thrusting visible from the one thruster in the camera's field of view, starting from just prior to landing burn ignition through touchdown.

The thruster pulses appear to be around 0.75 seconds long each, regularly spaced in time, though some are partially obscured by saturation from the main engine plume, and then there's a multi-second firing just before touchdown.

But, the thruster pulses are ineffective during most of the landing burn because overwhelmed by grid fin forces. It's only at the end when the stage has been slowed enough that the grid fins lose force and the thrusters can dominate. So where do you draw the line? It's not clear.

Having said that, it looks to me that only the last 4 seconds or so of RCS thrusting had an effect on roll, in concert with leg deployment.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/11/2018 04:22 am
The man in charge, meanwhile, said it was the engine.

If you are going to quote the man in charge, don't mis-quote. engineS. (so ... including RCS)

https://twitter.com/elonmusk/status/1070399755526656000

OK fair enough, so RCS is fair play based on Musk's statement.  Also, unlike the leg deployment, RCS can indeed bring the roll to zero.

Let's figure out how much they did tho.  Based on the videos, how long IYO were the RCS firing?

I get about 12 seconds of roll-correction thrusting visible from the one thruster in the camera's field of view, starting from just prior to landing burn ignition through touchdown.

The thruster pulses appear to be around 0.75 seconds long each, regularly spaced in time, though some are partially obscured by saturation from the main engine plume, and then there's a multi-second firing just before touchdown.

But, the thruster pulses are ineffective during most of the landing burn because overwhelmed by grid fin forces. It's only at the end when the stage has been slowed enough that the grid fins lose force and the thrusters can dominate. So where do you draw the line? It's not clear.

Having said that, it looks to me that only the last 4 seconds or so of RCS thrusting had an effect on roll, in concert with leg deployment.

Yes, agreed on the observations.

I can't find a good estimate on the force of the thrusters.  It's v*dm/dt, and v is probably 500-600, but I can't find dm/dt.   Given how quickly the thrusters flip a still-loaded stage around, they're not chump change, and 12 seconds is a lot of time.   From this, I draw the same conclusion you did - that during most of the time, the fins overwhelm the thrusters.

But the fins lose effectiveness towards the end (probably very non-linearly), and then both things happen - the legs deploy and cut the rotation speed as I calculated above, and the thrusters finally get their way.

As for the main engine - as explained by several people above - when there are external forces on the booster (such as gravity, aerodynamic loads, etc) a center engine can absolutely affect axial spin.  I think during that time, the fins are powerful enough that only something like the main engine can really fight them.

As an aside - I'm surprised by how much spare capacity the RCS thrusters had. 

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/11/2018 06:14 am
The fins have lost most of their control authority toward the final landing burn due to the deceased airflow though them as the velocity bled off as is drag on the entire vehicle. The gimbled throttle changes also imparted another torque though the CoG before touchdown righting the vehicle along with my previously mentioned torque (gyroscopic) during leg extension and the conservation of angular momentum. The roll RCS also had a great effect in reduction of rotation as well. Fuel load being burned off also has it's own contribution. Thus compound effects at play which is to be expected in complex motion...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jpo234 on 12/11/2018 07:17 am
Obviously, the reaction time for the engine gimbal is quicker than the rate of change imparted by that spin.
Which, yes, means that is one ridiculously nimble engine!
I expect they did this to make the propulsive landing possible in the first place, you do not want a large actuator lag for gimbal control on top of all the other control delays in the last few milliseconds of a landing.

Does anyone here have actual info on the max gimbal speed/rate of the center engine? For example, from first command to position achieved, how long for the engine to gimbal 4 degrees?
For that matter, just what is the maximum deflection achievable on that engine?

Oldie but goldie:

https://youtu.be/Pigsq5rt-mY
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jakusb on 12/11/2018 09:24 am
Obviously, the reaction time for the engine gimbal is quicker than the rate of change imparted by that spin.
Which, yes, means that is one ridiculously nimble engine!
I expect they did this to make the propulsive landing possible in the first place, you do not want a large actuator lag for gimbal control on top of all the other control delays in the last few milliseconds of a landing.

Does anyone here have actual info on the max gimbal speed/rate of the center engine? For example, from first command to position achieved, how long for the engine to gimbal 4 degrees?
For that matter, just what is the maximum deflection achievable on that engine?

Oldie but goldie:

https://www.youtube.com/watch?v=Pigsq5rt-mY

I understand how just 1 engine is not able to counter a spin as it can only target one direction at a time, but having it gimble in certain way (counter clockwise?) could it not help counter some spin? And what is the effect of the jet hitting the water? Would it not feedback in some way that might also kill any movement relative to the water?
Or does the jet only give upward energy and no counter spin energy as feedback?

Please Note: I only have a basic education in Theoretical Physics, so forgive me if above is a complete garbage reasoning.. ;)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: friendly3 on 12/11/2018 09:37 am
I understand how just 1 engine is not able to counter a spin as it can only target one direction at a time, but having it gimble in certain way (counter clockwise?) could it not help counter some spin? And what is the effect of the jet hitting the water? Would it not feedback in some way that might also kill any movement relative to the water?
Or does the jet only give upward energy and no counter spin energy as feedback?

How could a center engine gimbal counterclockwise?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: octavo on 12/11/2018 09:43 am
I understand how just 1 engine is not able to counter a spin as it can only target one direction at a time, but having it gimble in certain way (counter clockwise?) could it not help counter some spin? And what is the effect of the jet hitting the water? Would it not feedback in some way that might also kill any movement relative to the water?
Or does the jet only give upward energy and no counter spin energy as feedback?

How could a center engine gimbal counterclockwise?

Huh? The engine can gimbal in any direction. If you gimbal from center to north and then north east, then east, then southeast, then south- you are in effect gimballing counterclockwise, no?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jakusb on 12/11/2018 09:50 am
I understand how just 1 engine is not able to counter a spin as it can only target one direction at a time, but having it gimble in certain way (counter clockwise?) could it not help counter some spin? And what is the effect of the jet hitting the water? Would it not feedback in some way that might also kill any movement relative to the water?
Or does the jet only give upward energy and no counter spin energy as feedback?

How could a center engine gimbal counterclockwise?

Huh? The engine can gimbal in any direction. If you gimbal from center to north and then north east, then east, then southeast, then south- you are in effect gimballing counterclockwise, no?

That is indeed what I mean.. Also that energy should counter spin, would it not?
Only trouble would be that you need the gimbling to also steer the rocket to its intended landing spot..
So either they have foreseen this scenario and programmed to mitigate a spin (as much as possible), while steering at the same time...
The scenario is not that unthinkable, however countering a spin while steering does sound pretty complex, if not impossible... Then again, it clearly countered the spin in some way in the end.. ;)

My main question however is if it is theoratically possible there is feedback energy from the one jet hitting water? And such feedback that would also help counter spin...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: speedevil on 12/11/2018 09:56 am
That is indeed what I mean.. Also that energy should counter spin, would it not?
No.
Take a screwdriver, place it in a screw, and move it in a cone around the screw. It does not tighten or loosen the screw.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jakusb on 12/11/2018 10:00 am
That is indeed what I mean.. Also that energy should counter spin, would it not?
No.
Take a screwdriver, place it in a screw, and move it in a cone around the screw. It does not tighten or loosen the screw.

Ok, stand on a turning chair and sling something around... ;)
The engine gimbals outward not inward...
Some weight (engine bell) is effectively moved around the center axis..
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: octavo on 12/11/2018 10:08 am
That is indeed what I mean.. Also that energy should counter spin, would it not?
No.
Take a screwdriver, place it in a screw, and move it in a cone around the screw. It does not tighten or loosen the screw.

In this scenario the gimballing engine would be the screw, not the screwdriver. I'm not sure how you would get a screwdriver straight and get a screw to wobble in a cone under the screwdriver. That's why it's not a great analogy.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/11/2018 11:10 am
He's actually right. You could use both the engine bell and the exhaust volume inside it as an impromptu "reaction wheel" by constantly actuating in a circular matter. And since the gas volume is being continuously expelled it even acts a bit like a yoyo despin-weight in fluid form, so it would be able to give a continuous rotational force without saturating. You rotate a gas volume relative to the core, then get rid of it. (The resulting gas jet would have spiral shape and expand away from the core)

The effect is going to be miniscule and orders of magnitude below the aerodynamic effect of the grid fins or the effects achievable if the rotation axis goes NOT through the gimbal bearing. But if you were in vacuum and this is the only effect you can use, it might actually work.

It has no practical application to this particular core landing, but I don't think you can completely neglect it in vacuum. ;)

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/11/2018 11:24 am
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=46944.0;attach=1532170;sess=47262
https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=46944.0;attach=1532172;sess=47262

what a line-up.   Progress, Soyuz, Cygnus, Dragon.
Only missing, yet another Progress and another Soyuz on the other side of the station. This rules!
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jakusb on 12/11/2018 11:35 am
He's actually right. You could use both the engine bell and the exhaust volume inside it as an impromptu "reaction wheel" by constantly actuating in a circular matter. And since the gas volume is being continuously expelled it even acts a bit like a yoyo despin-weight in fluid form, so it would be able to give a continuous rotational force without saturating. You rotate a gas volume relative to the core, then get rid of it. (The resulting gas jet would have spiral shape and expand away from the core)

The effect is going to be miniscule and orders of magnitude below the aerodynamic effect of the grid fins or the effects achievable if the rotation axis goes NOT through the gimbal bearing. But if you were in vacuum and this is the only effect you can use, it might actually work.

It has no practical application to this particular core landing, but I don't think you can completely neglect it in vacuum. ;)

What about the effect of the jet hitting (not rotating, thus counter moving) water?
Would it move the water in rotating motion, or would it have no effect at all?
If it would move the water, it would also feedback to the core, would it not?

Or would the rotating energy of the jet hitting the water have no (significant) effect at all?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/11/2018 11:48 am
He's actually right. You could use both the engine bell and the exhaust volume inside it as an impromptu "reaction wheel" by constantly actuating in a circular matter. And since the gas volume is being continuously expelled it even acts a bit like a yoyo despin-weight in fluid form, so it would be able to give a continuous rotational force without saturating. You rotate a gas volume relative to the core, then get rid of it. (The resulting gas jet would have spiral shape and expand away from the core)

The effect is going to be miniscule and orders of magnitude below the aerodynamic effect of the grid fins or the effects achievable if the rotation axis goes NOT through the gimbal bearing. But if you were in vacuum and this is the only effect you can use, it might actually work.

It has no practical application to this particular core landing, but I don't think you can completely neglect it in vacuum. ;)

What about the effect of the jet hitting (not rotating, thus counter moving) water?
Would it move the water in rotating motion, or would it have no effect at all?
If it would move the water, it would also feedback to the core, would it not?

Or would the rotating energy of the jet hitting the water have no (significant) effect at all?

None. Energy or torque exchanged between air and water has no effect whatsoever on the core. Since the exhaust is entirely supersonic, there is no force transfer "backwards" through the gas stream, and the inflicted forces against the engine bell and thrust chamber are exactly the same, regardless of whether the gas jet hits a shockwave during supersonic retropropulsion, goes into vacuum, or hits a water surface. There is no change in chamber pressure.

There might be a miniscule effect once the jet+steam+water droplets reflected by the water surface briefly hits parts of the rocket such as the legs, but that is very minor compared to the legs touching the liquid water itself only a fraction of a second later.



Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/11/2018 01:09 pm
For a rocket in vacuum, a central engine can't affect spin.

When there are other non axial forces, like gravity and fin forces, the central engine creates force pairs with all of then and so creates torques in all directions and affects axial spin.

If the control system didn't take that into account, they'd get unexpected spin during engine operation.



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ABCD: Always Be Counting Down
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Kabloona on 12/11/2018 01:14 pm

Yes, agreed on the observations.

I can't find a good estimate on the force of the thrusters.  It's v*dm/dt, and v is probably 500-600, but I can't find dm/dt.   Given how quickly the thrusters flip a still-loaded stage around, they're not chump change, and 12 seconds is a lot of time.   From this, I draw the same conclusion you did - that during most of the time, the fins overwhelm the thrusters.

But the fins lose effectiveness towards the end (probably very non-linearly), and then both things happen - the legs deploy and cut the rotation speed as I calculated above, and the thrusters finally get their way.

As for the main engine - as explained by several people above - when there are external forces on the booster (such as gravity, aerodynamic loads, etc) a center engine can absolutely affect axial spin.  I think during that time, the fins are powerful enough that only something like the main engine can really fight them.

As an aside - I'm surprised by how much spare capacity the RCS thrusters had.

We might be able to get ballpark RCS thrust figures by considering the proposed application to Tesla roadsters. Everyday Astronaut did a writeup on that, in which he cited "speculation" that the thrusters were around 1,000-2,000 lbf.

https://everydayastronaut.com/spacex-rockets-on-the-new-tesla-roadster-seriously/

That seems reasonable in light of Musk's notion of putting 10 thrusters on a Tesla, and his somewhat tongue-in-cheek statement that the thrusters could enable "short hops," presumably meaning that if you put one downward-pointing thruster at each corner of the car, you could get T/W>1.

So let's assume as a minimum that the output of 4 thrusters > weight of one Tesla roadster. Add a driver and call the roadster 3,000 pounds loaded. Then if each thruster is 1,000 lbf, 4 thrusters gives you 4,000 lbf, for a T/W=4,000/3,000=1.33, definitely enough to achieve liftoff.

But of course, thrust depends on chamber pressure, and the thrusters may have higher thrust on F9's and lower thrust on roadsters, simply by using lower-pressure gas on the roadster for convenience (higher safety margin, less energy required to repressurize tanks while driving, etc) But Musk did say the Tesla thrusters would run on "ultra high pressure air," and "ultra high" sounds to me like F9 pressure territory.

So if if we assume that Tesla thrusters would run at the same "ultra high pressure" as F9 thrusters, 1,000 lbf sounds like a reasonable minimum, given that 4 placed at the corners would, in fact, enable the "short hops" that Elon mentioned.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: The Vorlon on 12/11/2018 02:57 pm
I would be REAL respectful of a tank that was at 1K PSI.  Just saying...
Title: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Herb Schaltegger on 12/11/2018 03:45 pm
I would be REAL respectful of a tank that was at 1K PSI.  Just saying...
Scuba tanks run 3 times higher than that and they get clanked around on docks and boat decks all over the world every minute of every day. Nothing special about 1,000 PSI per se. Only how robust the tank and fittings are (or aren’t) really matters.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/11/2018 03:48 pm
For a rocket in vacuum, a central engine can't affect spin.

When there are other non axial forces, like gravity and fin forces, the central engine creates force pairs with all of then and so creates torques in all directions and affects axial spin.

If the control system didn't take that into account, they'd get unexpected spin during engine operation.
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ABCD: Always Be Counting Down

The thrust force of a engine does not  affect spin on an axis which goes through that engine's center of thrust (the way the roll axis goes through the center engine on F9)

ignore the thrust for a moment.
The engine has 2-axis TVC, which means the engine can be tilted in both pitch and yaw direction. This means the mass of the engine bell can be moved slightly off-axis in two directions.

If you gyrate the TVC around its center position in a circular fashion, you are moving (the) mass ( of the engine bell) in a circle. Doing so generates torque.

This is very similar to a reaction wheel. You can create a torque force if you accelerate or decelerate this gyrating movement, but the force is not continuous, only momentarily while you accelerate or decelerate the gyration.

Now enter thrust:

Under thrust the engine bell is filled with gas under pressure. This gas is mostly accelerating backwards, propelling the vehicle forward. But the gyration of the engine bell also imparts a circular motion on this gas volume, while it traverses the engine bell. As such it carries a small but measurable rotational momentum

This gas continuously exits the engine bell out the rear and takes this rotational momentum with it. This is visible to an outside observer in that the exhaust stream now forms an expanding spiral pattern instead of straight backwards.

That means, while under thrust, the gyrating engine bell imparts momentum continuously on the exhaust gas, resulting in a torque force (measurable in higher force needed to move the TVC in a circle than there would be if there was no thrust, thanks to the extra mass of the gas volume that needs to be accelerated) this torque force in turn adds or substracts from the vehicles rotational momentum, spinning it up or slowing it down.

the effect is very small due to the small time the gas spends within the engine bell and the small extra acceleration the movement of the engine bell due to TVC actuation imparts on the gas compared to the overall thrust. But in vacuum this effect would be measurable and possibly usable.

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: edzieba on 12/11/2018 03:49 pm
Yep, 300 Bar (4350 PSI) is something I'd be happy to be around in a nice hefty steel tank. In a thin walled CoPV designed to be as light as possible without popping and making a big mess? Somewhat less happy.

On an unrelated note: Has anyone caught a photo of the inside of the interstage from the 'right' side (with the booster orientation assumed to be damaged-part-down)? John Kraus' fantastic photos (from the left side) during towing tantalisingly show the hydraulic feed lines vanishing under the left lip of the interstage, but hide the hydraulic equipment itself from view. There would be a lot of mysteries clarified by seeing how the grid-fin hydraulics are configured.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/11/2018 03:51 pm
If we're heading down the road of thruster thrust be mindful that its proportional (or at least related) to tank pressure and whatever pressure was available during the flip maneuver is likely to be significantly reduced by the time it gets close to landing in a normal landing and in this case where there was an ongoing battle between grid fins and thrusters I'd expect the pressure to be lower than what the designers had hoped for in their lowest pressure scenario.  Or not, maybe the tanks are vastly larger than necessary.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/11/2018 03:54 pm
If we're heading down the road of thruster thrust be mindful that its proportional (or at least related) to tank pressure and whatever pressure was available during the flip maneuver is likely to be significantly reduced by the time it gets close to landing in a normal landing and in this case where there was an ongoing battle between grid fins and thrusters I'd expect the pressure to be lower than what the designers had hoped for in their lowest pressure scenario.  Or not, maybe the tanks are vastly larger than necessary.
Good point.

Damn that system is complicated.

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ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Johnnyhinbos on 12/11/2018 04:01 pm
I would be REAL respectful of a tank that was at 1K PSI.  Just saying...
Scuba tanks run 3 times higher than that and they get clanked around on docks and boat decks all over the world every minute of every day. Nothing special about 1,000 PSI per se. Only how robust the tank and fittings are (or aren’t) really matters.


Well - true, and yet sadly people do die or get maimed by SCUBA tanks every year. An acquaintance of mine is in possession of the tank from the following incident from January.

Quote
Yesterday evening,There was an explosion of a dive tank on the Utila Cays,causing Mr Newton Diamond to lose his leg and Keily Pineda whom loss her life.

Mr Newton suffered a massive amount of blood loss and needed to be taken to La Ceiba immediately. Utila is a small island and news travels very fast,and being our airport doesn’t have lights,everyone with a vehicle got together and went up on the airport to shine the way for the airplane to takeoff.
He made it to La Ceiba safe where he was interned in the hospital for surgery. We’re happy to announce that he’s doing good,he will have a long and slow recovery but we have faith that he will be good.

Keily was only 16 years old and she loss her life in this tragic accident. Her family is from the mainland but she’s born and raised on the Utila Cays and her body will be laid to rest here.

We’d like to thank the entire community for coming together when called upon to help in time of need and also a special thanks to Captain Clint Gerner for your rapid response and generous contribution to saving Mr Newton’s life. We will forever be grateful for what you did for our community.

Thank you all.
-Utila 911 team
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/11/2018 04:34 pm
So if if we assume that Tesla thrusters would run at the same "ultra high pressure" as F9 thrusters, 1,000 lbf sounds like a reasonable minimum...

My guess would be that the Tesla thrusters run at whatever pressure your local scuba shop is willing to sell you, at least for the first shot.  Second shot at a lower pressure.  Third shot at a lower pressure.  And so on until you visit the scuba shop again. So maybe you go out onto an empty mall parking lot and try some really sharp high speed corners and are amazed at the 3G corners that it'll achieve.  Then after doing a few and getting the feel you go get your friend to show him / her (think of all the videos of passengers being shown Ludicrous acceleration) but by now the tank pressure is a small portion of what it was and you go off the road and into the forest and you and your friend get killed then re-killed by the COPV bursting.

That is one tank fill situation, fill it with air intermittently at the scuba shop.  But that would require that a) Tesla supplies a very long hose connect your car in the parking lot with the compressor in the shop, and b) that the tank be metal (vs. plastic composite) or that Tesla / SpaceX is OK with air (oxygen) in the composite tank, and c) that the tank be filled without being immersed in cooling water which most shops would probably not go along with, or d) that you would need to take the tank into the shop.

Other potential fill scenarios would be if the car had an onboard compressor (energy consumptive, inefficient, slow, potentially noisy), or you would be given a high pressure compressor at home.  And in in both cases they could choose to fill the tanks with air or with nitrogen separated from air.

Hmm, just thought of another option which seems to me very likely - You obtain liquid nitrogen locally and its stored in a dewar in the car to be warmed (hopefully with heat from a heat exchanger rather than battery) and the resulting high pressure gas stored for the next shot or two.

Now that I've given it some thought I've convinced me that the Spacex option package on Roadster is the case of Elon getting ahead of himself without thinking it through.  May the force be with the engineers he's assigned to make it happen.

Some may argue that I've digressed from strictly CRS-16 content in this post and that may be true.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Chris Bergin on 12/11/2018 05:15 pm
Yeah, people are reporting to mod over this, so back on topic please (as in from this post onwards).
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: jpo234 on 12/11/2018 06:43 pm
https://twitter.com/cygnusx112/status/1072541873724710913

Quote
The CBI truck backed up to the #Falcon9 and connected into the rear. They must be draining something before moving to the transporter. #SpaceX

For those wondering: CBI is Cliff Berry, Inc. (https://www.cliffberryinc.com/)
One of the services they provide is Marine & Onshore Tank Cleaning (https://www.cliffberryinc.com/services/industrial). This makes me think that they are draining RP1 contaminated sea water.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: llanitedave on 12/11/2018 07:55 pm
He's actually right. You could use both the engine bell and the exhaust volume inside it as an impromptu "reaction wheel" by constantly actuating in a circular matter. And since the gas volume is being continuously expelled it even acts a bit like a yoyo despin-weight in fluid form, so it would be able to give a continuous rotational force without saturating. You rotate a gas volume relative to the core, then get rid of it. (The resulting gas jet would have spiral shape and expand away from the core)

The effect is going to be miniscule and orders of magnitude below the aerodynamic effect of the grid fins or the effects achievable if the rotation axis goes NOT through the gimbal bearing. But if you were in vacuum and this is the only effect you can use, it might actually work.

It has no practical application to this particular core landing, but I don't think you can completely neglect it in vacuum. ;)


The gas generator also contributes a small amount of thrust, and it is off center.  So the combined thrust vector can actually have a slight effect on cancelling roll.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ellindsey on 12/11/2018 08:06 pm
He's actually right. You could use both the engine bell and the exhaust volume inside it as an impromptu "reaction wheel" by constantly actuating in a circular matter. And since the gas volume is being continuously expelled it even acts a bit like a yoyo despin-weight in fluid form, so it would be able to give a continuous rotational force without saturating. You rotate a gas volume relative to the core, then get rid of it. (The resulting gas jet would have spiral shape and expand away from the core)

The effect is going to be miniscule and orders of magnitude below the aerodynamic effect of the grid fins or the effects achievable if the rotation axis goes NOT through the gimbal bearing. But if you were in vacuum and this is the only effect you can use, it might actually work.

It has no practical application to this particular core landing, but I don't think you can completely neglect it in vacuum. ;)


The gas generator also contributes a small amount of thrust, and it is off center.  So the combined thrust vector can actually have a slight effect on cancelling roll.

Unless I'm mistaken, the gas generator and its exhaust are stationary on the Merlin 1D.  Only the combustion chamber and nozzle move.  That's certainly the way it appears from looking at the engine, and the hole in the insulation plate around the engine doesn't seem to allow the turbopump exhaust to move.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Zpoxy on 12/11/2018 09:19 pm
If we're heading down the road of thruster thrust be mindful that its proportional (or at least related) to tank pressure and whatever pressure was available during the flip maneuver is likely to be significantly reduced by the time it gets close to landing in a normal landing and in this case where there was an ongoing battle between grid fins and thrusters I'd expect the pressure to be lower than what the designers had hoped for in their lowest pressure scenario.  Or not, maybe the tanks are vastly larger than necessary.

Are you assuming the cold gas thrusters are connected directly to the supply tank? I'm sure there is a pressure regulator between the supply tank and the thrusters. Providing a relatively constant pressure and thrust until the tank goes flat.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Scylla on 12/11/2018 10:14 pm
Doing The Math On The Spinning Falcon 9 Booster
Scott Manley

Published on Dec 11, 2018
How much does deploying the landing legs change the rotation?
Let's run the numbers.
https://youtu.be/jaKGoiJCDXA
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/11/2018 11:52 pm
The stage landed at an angle so the final "coup de gras" arresting rotation was from one possibly two legs striking the water...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Kabloona on 12/12/2018 01:41 am
Doing The Math On The Spinning Falcon 9 Booster
Scott Manley

Published on Dec 11, 2018
How much does deploying the landing legs change the rotation?
Let's run the numbers.


Shorter Scott Manley for those who don't watch the video:

Leg deployment roughly doubles the roll moment of inertia.
So leg deployment by itself will reduce roll rate by about half.
(But increased MOI from leg deployment reduces effectiveness of RCS roll thrusters)

Graphical analysis of video shows RCS thrusters are in fact reducing roll rate *before* leg deployment.
Then leg deployment further reduces roll rate by increasing MOI.
But roll rate is not fully nulled before legs hit water.
Legs hitting water may have been the final factor in nulling the roll rate.

Hope I got that more or less correct. Thanks, Scott.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jdeshetler on 12/12/2018 02:37 am
I didn't expected that my twitter from Dec 6th to Scott would started this debate but that was cool!

https://twitter.com/jdeshetler/status/1070773216413605889
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/12/2018 07:42 am
Doing The Math On The Spinning Falcon 9 Booster
Scott Manley

Published on Dec 11, 2018
How much does deploying the landing legs change the rotation?
Let's run the numbers.


Shorter Scott Manley for those who don't watch the video:

Leg deployment roughly doubles the roll moment of inertia.
So leg deployment by itself will reduce roll rate by about half.
(But increased MOI from leg deployment reduces effectiveness of RCS roll thrusters)

Graphical analysis of video shows RCS thrusters are in fact reducing roll rate *before* leg deployment.
Then leg deployment further reduces roll rate by increasing MOI.
But roll rate is not fully nulled before legs hit water.
Legs hitting water may have been the final factor in nulling the roll rate.

Hope I got that more or less correct. Thanks, Scott.
Scott's a good guy.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: graywolf on 12/12/2018 01:53 pm
>>> But increased MOI from leg deployment reduces effectiveness of RCS roll thrusters

This scratched my ears first time when I watched Scott's video and now it is on NASA forum.
IMO, this is not correct.

Remember momentum conservation law.

The speed of rotation has slowed down 1/2x, because MOI doubled after legs were deployed, so for the body to keep the same momentum, the speed of rotation should be halved.

RCS should fight against F9's momentum. It does not matter if legs are deployed or not. The momentum is the same (well provided we do not have any more forces adding to rotation, which in case of deployed legs is probabaly negative, that is the legs are slowing rotation down due to air resistance, and then due to water resistance).

My point is: RCS effectiveness in roll elimination have not changed with legs deployment.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/12/2018 01:57 pm
>>> But increased MOI from leg deployment reduces effectiveness of RCS roll thrusters

This scratched my ears first time when I watched Scott's video and now it is on NASA forum.
IMO, this is not correct.

Remember momentum conservation law.

The speed of rotation has slowed down 1/2x, because MOI doubled after legs were deployed, so for the body to keep the same momentum, the speed of rotation should be halved.

RCS should fight against F9's momentum. It does not matter if legs are deployed or not. The momentum is the same (well provided we do not have any more forces adding to rotation, which in case of deployed legs is probabaly negative, that is the legs are slowing rotation down due to air resistance, and then due to water resistance).

My point is: RCS effectiveness in roll elimination have not changed with legs deployment.
Leg touching water, that I obviously buy.

Maybe that's why one leg was lost, too.

Did they ever fish it out?  I mean they have the exact surface coordinate, and a good estimate of surface currents...



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ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Kabloona on 12/12/2018 02:22 pm
>>> But increased MOI from leg deployment reduces effectiveness of RCS roll thrusters

This scratched my ears first time when I watched Scott's video and now it is on NASA forum.
IMO, this is not correct.

Remember momentum conservation law.

The speed of rotation has slowed down 1/2x, because MOI doubled after legs were deployed, so for the body to keep the same momentum, the speed of rotation should be halved.

RCS should fight against F9's momentum. It does not matter if legs are deployed or not. The momentum is the same (well provided we do not have any more forces adding to rotation, which in case of deployed legs is probabaly negative, that is the legs are slowing rotation down due to air resistance, and then due to water resistance).

My point is: RCS effectiveness in roll elimination have not changed with legs deployment.

You are correct insofar as conservation of momentum is concerned, ie for a given quantity of stored angular momentum, the RCS thrusters will have to impart a constant amount of angular impulse (torque x time) to null it out, regardless of leg position.

But Scott's point was that  a fixed RCS thrust will impart less angular acceleration to the rocket with the legs extended. That is what he meant by "reduced effectiveness."

And he may have been of the mind that some aerodynamic force, although reduced, may still have been inducing roll torque through the grid fins, so the RCS thrusters may still have been fighting the grid fins, not just stored angular momentum. In which case, their "effectiveness", ie induced angular acceleration for an RCS pulse of given duration, would indeed be reduced.

You are both correct, but emphasizing different points.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/12/2018 02:25 pm
>>> But increased MOI from leg deployment reduces effectiveness of RCS roll thrusters

This scratched my ears first time when I watched Scott's video and now it is on NASA forum.
IMO, this is not correct.

Remember momentum conservation law.

The speed of rotation has slowed down 1/2x, because MOI doubled after legs were deployed, so for the body to keep the same momentum, the speed of rotation should be halved.

RCS should fight against F9's momentum. It does not matter if legs are deployed or not. The momentum is the same (well provided we do not have any more forces adding to rotation, which in case of deployed legs is probabaly negative, that is the legs are slowing rotation down due to air resistance, and then due to water resistance).

My point is: RCS effectiveness in roll elimination have not changed with legs deployment.
The rate of decrease of angular momentum will remain the same after legs are deployed. if

The rate of decrease of rotation rate (which is prolly what we mean by "effectiveness") will be lower once the legs are out.

So here's a riddle:  if you had X amount of stored gas, and ignoring the grid fins for a second - would you want to expend it before or after leg deployment?

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ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/12/2018 02:32 pm

If the control system didn't take that into account, they'd get unexpected spin during engine operation.


That is what RCS is for.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/12/2018 02:36 pm
>>> But increased MOI from leg deployment reduces effectiveness of RCS roll thrusters

This scratched my ears first time when I watched Scott's video and now it is on NASA forum.
IMO, this is not correct.

Remember momentum conservation law.

The speed of rotation has slowed down 1/2x, because MOI doubled after legs were deployed, so for the body to keep the same momentum, the speed of rotation should be halved.

RCS should fight against F9's momentum. It does not matter if legs are deployed or not. The momentum is the same (well provided we do not have any more forces adding to rotation, which in case of deployed legs is probabaly negative, that is the legs are slowing rotation down due to air resistance, and then due to water resistance).

My point is: RCS effectiveness in roll elimination have not changed with legs deployment.
Welcome to the forum! :) The mass is conserved but the distribution has changed and so has the angular velocity. The RCS will lose some effectiveness do to having to act from a shorter lever arm relative to the tip of the extended legs...
https://www.grc.nasa.gov/www/k-12/airplane/angdva.html
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Kabloona on 12/12/2018 02:43 pm
>>> But increased MOI from leg deployment reduces effectiveness of RCS roll thrusters

This scratched my ears first time when I watched Scott's video and now it is on NASA forum.
IMO, this is not correct.

Remember momentum conservation law.

The speed of rotation has slowed down 1/2x, because MOI doubled after legs were deployed, so for the body to keep the same momentum, the speed of rotation should be halved.

RCS should fight against F9's momentum. It does not matter if legs are deployed or not. The momentum is the same (well provided we do not have any more forces adding to rotation, which in case of deployed legs is probabaly negative, that is the legs are slowing rotation down due to air resistance, and then due to water resistance).

My point is: RCS effectiveness in roll elimination have not changed with legs deployment.
Welcome to the forum! :) The mass is conserved but the distribution has changed and so has the angular velocity. The RCS will lose some effectiveness do to having to act from a shorter lever arm relative to the tip of the extended legs...
https://www.grc.nasa.gov/www/k-12/airplane/angdva.html

Graywolf is correct as far as he goes. Assuming a fixed quantity of stored momentum, it will take the same amount of RCS total angular impulse (torque x time) to zero out that angular momentum.

The only difference between legs closed or legs extended, in the ideal case, is that with legs closed the stage is rolling faster with lower MOI, and with legs extended the stage rolls slower with higher MOI. But since total angular momentum remains the same (MOI x roll rate), in each case the RCS thruster will need a burn of the same duration to cancel out the spin.

The RCS thrusters don't know nor care where the angular momentum is "stored" on the stage. But as long as that quantity remains fixed, a fixed torque applied for a fixed duration will null it out.

But, yes, the RCS thruster torque will induce less angular acceleration with legs extended, due to increased MOI.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/12/2018 02:54 pm
>>> But increased MOI from leg deployment reduces effectiveness of RCS roll thrusters

This scratched my ears first time when I watched Scott's video and now it is on NASA forum.
IMO, this is not correct.

Remember momentum conservation law.

The speed of rotation has slowed down 1/2x, because MOI doubled after legs were deployed, so for the body to keep the same momentum, the speed of rotation should be halved.

RCS should fight against F9's momentum. It does not matter if legs are deployed or not. The momentum is the same (well provided we do not have any more forces adding to rotation, which in case of deployed legs is probabaly negative, that is the legs are slowing rotation down due to air resistance, and then due to water resistance).

My point is: RCS effectiveness in roll elimination have not changed with legs deployment.
Welcome to the forum! :) The mass is conserved but the distribution has changed and so has the angular velocity. The RCS will lose some effectiveness do to having to act from a shorter lever arm relative to the tip of the extended legs...
https://www.grc.nasa.gov/www/k-12/airplane/angdva.html

No, graywolf is correct as far as he goes. Assuming a fixed quantity of stored momentum, it will take the same amount of RCS total angular impulse (torque x time) to zero out that angular momentum.

The only difference between legs closed or legs extended, in the ideal case, is that with legs closed the stage is rolling faster with lower MOI, and with legs extended the stage rolls slower with higher MOI. But since total angular impulse remains the same (MOI x roll rate), in each case the RCS thruster will need a burn of the same duration to cancel out the spin.

The RCS thrusters don't know nor care "where" the angular momentum is stored on the stage. But as long as that quantity remains fixed, a fixed torque applied for a fixed duration will null it out.
Here is a good explanation of "my madness"... ;D
https://www.quora.com/What-is-the-difference-between-angular-momentum-and-angular-velocity
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Kabloona on 12/12/2018 02:58 pm
Yes, I think we all understand high school physics. can we move on now?  :)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/12/2018 03:07 pm
>>> But increased MOI from leg deployment reduces effectiveness of RCS roll thrusters

This scratched my ears first time when I watched Scott's video and now it is on NASA forum.
IMO, this is not correct.

Remember momentum conservation law.

The speed of rotation has slowed down 1/2x, because MOI doubled after legs were deployed, so for the body to keep the same momentum, the speed of rotation should be halved.

RCS should fight against F9's momentum. It does not matter if legs are deployed or not. The momentum is the same (well provided we do not have any more forces adding to rotation, which in case of deployed legs is probabaly negative, that is the legs are slowing rotation down due to air resistance, and then due to water resistance).

My point is: RCS effectiveness in roll elimination have not changed with legs deployment.
Leg touching water, that I obviously buy.

Maybe that's why one leg was lost, too.

Did they ever fish it out?  I mean they have the exact surface coordinate, and a good estimate of surface currents...



-----
ABCD: Always Be Counting Down

Yes, the leg was removed by divers the first day that the booster was floating outside Port Canavera.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/12/2018 03:08 pm
Yes, I think we all understand high school physics. can we move on now?  :)
College level... ;) How about: Saltwater intrusion and re-use? ??? ;D
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/12/2018 03:32 pm
Yes, I think we all understand high school physics. can we move on now?  :)
Saltwater intrusion and re-use? ??? ;D

Better: Visible damage on various engine bells, potential origin and implications.

Assuming the engines are not affected by corrosion, which obviously caused surface discoloration.

Which damages can be banged out, ignored, or repaired.

Can the engine bell be easily replaced? It has regen cooling channels inside, right?

Aside from the massively dented in bell, at least one shows scratches/ dents which seem to come from the chains used during salvage.

How severe is thermal shock of being immereed in water while running? Would that crack it? center engine only or all?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/12/2018 03:43 pm
Yes, I think we all understand high school physics. can we move on now?  :)
Saltwater intrusion and re-use? ??? ;D

Better: Visible damage on various engine bells, potential origin and implications.

Assuming the engines are not affected by corrosion, which obviously caused surface discoloration.

Which damages can be banged out, ignored, or repaired.

Can the engine bell be easily replaced? It has regen cooling channels inside, right?

Aside from the massively dented in bell, at least one shows scratches/ dents which seem to come from the chains used during salvage.

How severe is thermal shock of being immereed in water while running? Would that crack it? center engine only or all?
Old H-1 test...
http://up-ship.com/blog/?p=5948
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/12/2018 03:56 pm
>>> But increased MOI from leg deployment reduces effectiveness of RCS roll thrusters

This scratched my ears first time when I watched Scott's video and now it is on NASA forum.
IMO, this is not correct.

Remember momentum conservation law.

The speed of rotation has slowed down 1/2x, because MOI doubled after legs were deployed, so for the body to keep the same momentum, the speed of rotation should be halved.

RCS should fight against F9's momentum. It does not matter if legs are deployed or not. The momentum is the same (well provided we do not have any more forces adding to rotation, which in case of deployed legs is probabaly negative, that is the legs are slowing rotation down due to air resistance, and then due to water resistance).

My point is: RCS effectiveness in roll elimination have not changed with legs deployment.
Leg touching water, that I obviously buy.

Maybe that's why one leg was lost, too.

Did they ever fish it out?  I mean they have the exact surface coordinate, and a good estimate of surface currents...



-----
ABCD: Always Be Counting Down

Yes, the leg was removed by divers the first day that the booster was floating outside Port Canavera.

I forgot.  Much respect for the people who did that, btw, and on such short notice.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: codav on 12/12/2018 04:07 pm
Assuming the engines are not affected by corrosion, which obviously caused surface discoloration.
 of being immereed in water while running? Would that crack it? center engine only or all?

Which damages can be banged out, ignored, or repaired.

Ideally, salt water ingression into the plumbing should be quite minimal, as the Merlin engine uses pintle injectors. These stop both the RP-1 and LOX flows like a valve, so no water should be able to enter via the injector plate. The only way water might get into the engine is via the preburner exhaust. Even if salt water got inside, the materials used in the plumbing, turbopump etc. should not get corroded as they need to withstand the hot, almost pure oxygen from the preburner. Even the H-1 engine, which wasn't really built for reusability, could be refurbished for 5% the cost of a new engine. As SpaceX has a lot of experience with their engines, refurbishment will certainly be easier an cheaper.

As for the engine bells, those wwhich sustained heavier damage will be replaced for sure.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rocket Science on 12/12/2018 04:28 pm
Submerge the entire stage in a makeshift freshwater tank then attend to all the electrical systems... Be a great test for WD-40... ;) ;D Corporate sponsor for a test flight...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: whitelancer64 on 12/12/2018 04:34 pm
Yes, I think we all understand high school physics. can we move on now?  :)
Saltwater intrusion and re-use? ??? ;D

Better: Visible damage on various engine bells, potential origin and implications.

Assuming the engines are not affected by corrosion, which obviously caused surface discoloration.

Which damages can be banged out, ignored, or repaired.

Can the engine bell be easily replaced? It has regen cooling channels inside, right?

Aside from the massively dented in bell, at least one shows scratches/ dents which seem to come from the chains used during salvage.

How severe is thermal shock of being immereed in water while running? Would that crack it? center engine only or all?
Old H-1 test...
http://up-ship.com/blog/?p=5948

Worthwhile to note that the salt water exposure times were 1, 2 and 9 hours for each test, and the engines were immediately cleaned afterwards.

Still, that's a reasonably good data point that could be hopeful for these Merlin engines.

Attached image from test.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/12/2018 08:46 pm
Yes, I think we all understand high school physics. can we move on now?  :)
Saltwater intrusion and re-use? ??? ;D

Better: Visible damage on various engine bells, potential origin and implications.

Assuming the engines are not affected by corrosion, which obviously caused surface discoloration.

Which damages can be banged out, ignored, or repaired.

Can the engine bell be easily replaced? It has regen cooling channels inside, right?

Aside from the massively dented in bell, at least one shows scratches/ dents which seem to come from the chains used during salvage.

How severe is thermal shock of being immereed in water while running? Would that crack it? center engine only or all?
Old H-1 test...
http://up-ship.com/blog/?p=5948

Worthwhile to note that the salt water exposure times were 1, 2 and 9 hours for each test, and the engines were immediately cleaned afterwards.

Still, that's a reasonably good data point that could be hopeful for these Merlin engines.

Attached image from test.

Are you saying the times stated in the blog linked above are incorrect? 1, 2 and 9 matches the fully submerged, half submerged and on-water-surface times of test # 3 in 1962 in that document, but they also mentoon a 1 hour submerged, 2 hour half submerged, 2 hour surface and then a 12 hour waiting period before cleaning/flushing in test #2 1961. Was the same engine used for all 3 tests?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: OxCartMark on 12/12/2018 11:27 pm
If we're heading down the road of thruster thrust be mindful that its proportional (or at least related) to tank pressure and whatever pressure was available during the flip maneuver is likely to be significantly reduced by the time it gets close to landing in a normal landing and in this case where there was an ongoing battle between grid fins and thrusters I'd expect the pressure to be lower than what the designers had hoped for in their lowest pressure scenario.  Or not, maybe the tanks are vastly larger than necessary.

Are you assuming the cold gas thrusters are connected directly to the supply tank? I'm sure there is a pressure regulator between the supply tank and the thrusters. Providing a relatively constant pressure and thrust until the tank goes flat.

Why would you put a regulator in between the tank and thruster??  That would be a tremendous waste of energy, it would reduce thrust to its lowest planned level no matter what the available tank pressure.  Larger and heavier tanks would be needed.  Better to use whatever pressure is available and compensate in software ~ shorter bursts at high pressure and longer bursts at low pressure to obtain a desired impulse.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: envy887 on 12/13/2018 01:15 am
If we're heading down the road of thruster thrust be mindful that its proportional (or at least related) to tank pressure and whatever pressure was available during the flip maneuver is likely to be significantly reduced by the time it gets close to landing in a normal landing and in this case where there was an ongoing battle between grid fins and thrusters I'd expect the pressure to be lower than what the designers had hoped for in their lowest pressure scenario.  Or not, maybe the tanks are vastly larger than necessary.

Are you assuming the cold gas thrusters are connected directly to the supply tank? I'm sure there is a pressure regulator between the supply tank and the thrusters. Providing a relatively constant pressure and thrust until the tank goes flat.

Why would you put a regulator in between the tank and thruster??  That would be a tremendous waste of energy, it would reduce thrust to its lowest planned level no matter what the available tank pressure.  Larger and heavier tanks would be needed.  Better to use whatever pressure is available and compensate in software ~ shorter bursts at high pressure and longer bursts at low pressure to obtain a desired impulse.

In a vacuum where RCS is primarily used, exhaust velocity is constant for all chamber pressures, to first order. So using a regulator doesn't cost any energy, and allows the hardware to be optimized for a single chamber pressure rather than overbuilt for the max tank pressure.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Brian45 on 12/14/2018 04:11 pm
Watching the GPS III static fire video from US Launch Report, https://www.youtube.com/watch?v=0rUhw1Wf54c, at the end they added some "bonus" footage of the CRS-16 booster being processed for transportation.

They show the legs being removed. Was this done in this specific instance (because of the landing issues) and is not part of the normal post landing processing for the Block 5 booster? I thought that the legs would not need to be removed in normal circumstances.


Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Lars-J on 12/14/2018 04:30 pm
Legs are still removed from all Block 5 boosters. They still have issues to work out before they can just fold them up.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/14/2018 05:12 pm
For a rocket in vacuum, a central engine can't affect spin.

When there are other non axial forces, like gravity and fin forces, the central engine creates force pairs with all of then and so creates torques in all directions and affects axial spin.

If the control system didn't take that into account, they'd get unexpected spin during engine operation


Roll, which is a rotational on the longitudinal axis (body fixed coordinates).  Spin is not part of the discussion.  A spin is rotation in multiple axis.   
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Jim on 12/14/2018 05:20 pm
If we're heading down the road of thruster thrust be mindful that its proportional (or at least related) to tank pressure and whatever pressure was available during the flip maneuver is likely to be significantly reduced by the time it gets close to landing in a normal landing and in this case where there was an ongoing battle between grid fins and thrusters I'd expect the pressure to be lower than what the designers had hoped for in their lowest pressure scenario.  Or not, maybe the tanks are vastly larger than necessary.

Are you assuming the cold gas thrusters are connected directly to the supply tank? I'm sure there is a pressure regulator between the supply tank and the thrusters. Providing a relatively constant pressure and thrust until the tank goes flat.

Why would you put a regulator in between the tank and thruster??  That would be a tremendous waste of energy, it would reduce thrust to its lowest planned level no matter what the available tank pressure.  Larger and heavier tanks would be needed.  Better to use whatever pressure is available and compensate in software ~ shorter bursts at high pressure and longer bursts at low pressure to obtain a desired impulse.

In a vacuum where RCS is primarily used, exhaust velocity is constant for all chamber pressures, to first order. So using a regulator doesn't cost any energy, and allows the hardware to be optimized for a single chamber pressure rather than overbuilt for the max tank pressure.

And it provides a known thrust level. 
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meekGee on 12/14/2018 05:56 pm
For a rocket in vacuum, a central engine can't affect spin.

When there are other non axial forces, like gravity and fin forces, the central engine creates force pairs with all of then and so creates torques in all directions and affects axial spin.

If the control system didn't take that into account, they'd get unexpected spin during engine operation


Roll, which is a rotational on the longitudinal axis (body fixed coordinates).  Spin is not part of the discussion.  A spin is rotation in multiple axis.
Yes we clarified that before.  Lots of posts using the term spin informally, as in "spin about its axis" - meaning roll.  My posts sometimes too.

-----
ABCD: Always Be Counting Down

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: meberbs on 12/14/2018 05:57 pm
For a rocket in vacuum, a central engine can't affect spin.

When there are other non axial forces, like gravity and fin forces, the central engine creates force pairs with all of then and so creates torques in all directions and affects axial spin.

If the control system didn't take that into account, they'd get unexpected spin during engine operation

Roll, which is a rotational on the longitudinal axis (body fixed coordinates).  Spin is not part of the discussion.  A spin is rotation in multiple axis.
Again, you cannot separate these concepts. Angular momentum (spin as you are calling it) is not fixed to body axes. The thing you are trying to discuss about a "roll" fixed to a body axis is not a thing that actually exists. The conversation is about reality, no matter how many times you claim otherwise, generic spin is inherent to the discussion.

Even if everything else was magically perfect, the engine itself could produce a torque which would make the spin off body axis, giving the engine the control authority to cancel the spin. (This may not be the best general solution when other control options exist, but it is a contribution.)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: kdhilliard on 12/15/2018 01:13 pm
Watching the GPS III static fire video from US Launch Report, at the end they added some "bonus" footage of the CRS-16 booster being processed for transportation.
Two other items of note in that video:
* At 3:57 the video fades between the "upper" leg being removed while the stage is resting on ground supports to the stage being secured to its transporter, and from the position of the dented engine nozzle it is clear that they rolled the stage about 135° in the process. (Link (https://youtube.com/watch?v=0rUhw1Wf54c&t=227) to 10s before the fade.)
* At 4:52 the video fades between the booster being secured to its transporter and an edge-on close-up of the engine bay showing a lot of plumbing where some shielding was removed.  (Link (https://youtube.com/watch?v=0rUhw1Wf54c&t=282) to 10s before the fade.)

Edit: Fixed link.  (Removed the "www." so the YouTube video doesn't embed.)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: AJW on 12/18/2018 11:17 pm
With aircraft, you are taught early on to do pre-flight control checks.  This is sometimes referred to as 'boxing the controls', because you run through each control and push it to the minimum and maximum range twice while also visually checking the control surface to verify proper movement.   You will see rocket engines go through a gimbal check to verify their movement for the same reasons.

Is SpaceX able to do a pre-flight control check of the grid fins?   This would require that they have the ability to retract which I haven't seen.   They were also originally built with an open hydraulic system.  If this is still the case, any tests would deplete the reservoir.

Anyone with knowledge on how or when this system is checked before a flight?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Stan-1967 on 12/18/2018 11:42 pm
The grid fins deploy when S1 is in free fall, and they are also carry some not insignificant mass.  I wonder if the hydraulics do not have power to deploy them when under 1g, therefore they can’t be ground checked when S1 is vertical under its own internal power.  Deployment also looks s bit non linear, like it is spring loaded or something.  Actual control inputs are rotational, and give 2 axis control only.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Steven Pietrobon on 12/19/2018 02:56 am
New Shepard tests its fins before launch. The fins on Falcon 9 now use closed loop hydraulics. It should be possible to test the fins using external power on Falcon 9 before launch. SpaceX may choose to do that in future.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/19/2018 07:25 am
The grid fins deploy when S1 is in free fall, and they are also carry some not insignificant mass.  I wonder if the hydraulics do not have power to deploy them when under 1g, therefore they can’t be ground checked when S1 is vertical under its own internal power.  Deployment also looks s bit non linear, like it is spring loaded or something.  Actual control inputs are rotational, and give 2 axis control only.

Afair, Falcon9 used to retract the fins on its own after landing, during saving procedure. They also extended them under 1 G on F9RDev1 flights, although those were lighter aluminum fins and a dev vehicle.

It could be something mundane like physically being in the way of the TE that prevents a full actuation test on the pad. Or they just didn't bother since the system wasnt mission critical until now.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Danny452 on 12/19/2018 12:32 pm
Testing booster recovery equipment is not like testing other equipment as booster recovery is of no advantage to the customer.  If you test the fins and they fail the test what do you do?  You have to choose between delaying the customer's launch (if possible) and expending the booster.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 12/19/2018 01:49 pm
Testing booster recovery equipment is not like testing other equipment as booster recovery is of no advantage to the customer.  If you test the fins and they fail the test what do you do?  You have to choose between delaying the customer's launch (if possible) and expending the booster.

Still useful. If SpaceX had known that the Gridfins were inoperational, they would have chosen a contingency approach in cooperation with the customer. Either:

- stand down and fix the issue
or
- forgo recovery. No boostback burn, splashdown in NOTMAR/NOTAM designated exclusion zone


We wouldn't have seen the scary imagery of a booster tumbling out of control over the cape, nor its unexpected but highly impressive recovery and water landing.

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: llanitedave on 12/20/2018 11:53 pm
Testing booster recovery equipment is not like testing other equipment as booster recovery is of no advantage to the customer.  If you test the fins and they fail the test what do you do?  You have to choose between delaying the customer's launch (if possible) and expending the booster.


Once you set your pricing under the paradigm of recovery and reuse, then booster recovery IS an advantage to the customer, and scrubbing a launch on a threat to recoverability makes perfect sense.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: llanitedave on 12/20/2018 11:55 pm
The grid fins deploy when S1 is in free fall, and they are also carry some not insignificant mass.  I wonder if the hydraulics do not have power to deploy them when under 1g, therefore they can’t be ground checked when S1 is vertical under its own internal power.  Deployment also looks s bit non linear, like it is spring loaded or something.  Actual control inputs are rotational, and give 2 axis control only.

Afair, Falcon9 used to retract the fins on its own after landing, during saving procedure. They also extended them under 1 G on F9RDev1 flights, although those were lighter aluminum fins and a dev vehicle.

It could be something mundane like physically being in the way of the TE that prevents a full actuation test on the pad. Or they just didn't bother since the system wasnt mission critical until now.


Maybe that check could be done after the partial retraction of the TE?
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Stan-1967 on 12/21/2018 02:50 am
Maybe that check could be done after the partial retraction of the TE?

I think it is possible the only time they could do a hydraulic check ( for RTLS ) is the short span of around 3 minutes between the end of the boostback burn, and just prior to the re-entry burn.  I think it is an unknown trade as to the power budget needed to keep the hydraulics active for an extra 3 minutes, but operationally, I think it only makes sense to do any testing before re-entry.  Furthermore, the failure was with the hydraulics that actuate the grid fins, not with the deployment of the fins.  It is being assumed by many that these events are controlled by the same sub-system.  I do not think they are, so ground testing is not enabled by adding redundancy to the hydraulics if the systems are separate.

The rest of this post is a bit lengthy, but I'll try to explain why;

1.  If an anomaly is detected in the grid fin hydraulics before re-entry, the flight software can divert to a safer distance offshore during the entry burn.  It makes no sense to stop RTLS while SpaceX investigates this, the overall record is still very good, & other precautions can be done.

2.  This is not an issue that concerns customers, with the exception of when your customer also owns the launch range.  It concerns CCAFS, & as demonstrated with the last launch from Vandenberg, that customer weighed risk & said no too RTLS coming anywhere near their pads & other payloads.

2.  I think video of past RTLS missions suggest grid fin deployment is done with springs, not hydraulics. ( note SpaceX does use springs for S1/S2 separation, & fairing sep.  They like springs.) 

3.  If the size & weight of a spring that deploys in zero g vs. under 1 g is a significant weight penalty.  The prudent rocket engineer will size for zero g & this choice is why it can't be ground tested. 

4.  Using springs vs. hydraulics for fin deployment is likely a weight trade against the hydraulic reservoir, piston stroke, & needed force duration for translating the grid fin joint in a rotational axis that changes roll/pitch only vs. adding what would basically be yaw control in the deployment translation mode.

5.  This is not comparable to F9Dev, New Shepard, or an airplanes pre-flight.  F9Dev & New Shepard do not have the weight priorities of an orbital booster.  Both had a T/W that could throttle on either side of 1.0, so both had margin for more robust systems than would be included on an orbital booster.   Airplanes have payload mass fractions no rocket will ever touch, so the built in safety features are not comparable.

Here are some YT clips showing what I am talking about.  I have tried to cut/paste at the relevant time stamp, but YT wants to show you commercials first.  I have included the clock time in comments so you can forward to the relevant time.

F9Dev vehicle:
Deployment of fins at altitude takes less than 1s, ( 14'12" mark) &  folded down immediately after landing. Quick motions indicate excess hydraulic power margins.  F9DEV purpose was to make powered landings work by learning the control laws for low speed flight regime, it was not to engineer the systems.
https://youtu.be/AllaFzIPaG4?t=853


CRS-13 webcast:
Grid fin deployment at 19:38, ends by 19:49, so around 10s deployment time. Deployment is uneven & jumpy ( like an under damped spring) .  Fins bounce at end of deployment & then presumably lock into place or bounce is dampened out.
https://youtu.be/OPHbqY9LHCs?t=1178


CRS-16 webcast:
Deployment starts at 18:41, ends at around 19:10.  Deployment is symmetrical fin to fin, but jumpy in deployment. Aero forces start roll at around 22:05, a 3'30" interval where hydraulics could be tested before re-entry burn.
https://youtu.be/Esh1jHT9oTA?t=1121

Another take-away is that the grid fin hydraulics look like they are evolving.  That is expected from F9Dev into block 1.0, 1.1, FT, but even comparing CRS-13 ( block FT) against CRS-16 ( Block 5) , they do not perform the same.  The system is changing.  No surprise given this is SpaceX.

Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: mn on 12/21/2018 03:41 am

...
. ( note SpaceX does use springs for S1/S2 separation, & fairing sep.  They like springs.) 
...


I'm pretty sure stage separation is pneumatic. (High pressure helium if I'm not mistaking)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Stan-1967 on 12/21/2018 04:30 am

...
. ( note SpaceX does use springs for S1/S2 separation, & fairing sep.  They like springs.) 
...


I'm pretty sure stage separation is pneumatic. (High pressure helium if I'm not mistaking)

You are correct.  Section 2.3 of the F9 users guide confirm S1/S2 separation is driven by a high pressure pneumatic helium source.  So is the fairing separation.

I'll defend myself a bit & say I think it's fair to consider a pneumatic pusher as a type of spring. :-) 

My original thinking was however that it was mechanical, so I erred in that.  To the points I made, using the existing high pressure helium to deploy the heavy grid fins seems consistent with a favorable trade against oversizing the hydraulics for ground test or deployment under gravity.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: gongora on 12/26/2018 07:07 pm
Thorlabs in orbit: Space station hosts optical fiber experiment (https://www.njherald.com/20181226/thorlabs-in-orbit-space-station-hosts-experiment#)
Quote
Inside that 21-inch-by-18-inch-by-11-inch box is a self-contained factory using the near-weightlessness of space to pull high quality optic fiber from highly technical glass.
...
As Saad talked about the project last week on the upper floors of Thorlabs' headquarters on Sparta Avenue, more than 250 miles higher still, astronauts were installing the third box in a series of four that make up this stage of experiments.

The third box was delivered to the ISS on Dec. 8, aboard the SpaceX-16 mission and returns to Earth early next year when the docking vehicle leaves the station. A fourth box will be delivered aboard SpaceX-17, due to launch in March.

Saad heads up the Thorlabs team that is working with a team from a California-based company, Made in Space, which is providing the mechanics of the glass-pulling "factory" in the box.
...
The glass being used in the ISS experiments is made from a group of fluoride compounds.

The difference between glass fiber made from silica and fiber drawn from fluoride is the wavelengths of light that can be transmitted along the fiber.
...
Saad said the first two flights of the production box on ISS did not produce any fiber because of mechanical issues.
...
The result was blobs of glass, rather than strings of glass.

In this third box, the glass is pulled along and it's hoped strands of fiber will result. The box has three "pre-forms," specific size, shape and weight pieces of pure glass, which can be pulled into a total of 1.5 kilometers (0.93 miles) of optic fiber.
...
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Comga on 12/27/2018 02:37 am
(Snip)
I'll defend myself a bit & say I think it's fair to consider a pneumatic pusher as a type of spring. :-) 

My original thinking was however that it was mechanical, so I erred in that.  To the points I made, using the existing high pressure helium to deploy the heavy grid fins seems consistent with a favorable trade against oversizing the hydraulics for ground test or deployment under gravity.

Titanium grid fins are not “heavy” in free-fall. 😉
They are massive, but the power to deploy them is inverse to the speed of deployment. (Even under 1g)
However, the power to actuate them against the airstream must be huge.
The scaling of the hydraulic actuation system is unlikely to be effected by deployment.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Stan-1967 on 12/27/2018 05:47 am

Titanium grid fins are not “heavy” in free-fall. 😉
They are massive, but the power to deploy them is inverse to the speed of deployment. (Even under 1g)
However, the power to actuate them against the airstream must be huge.
The scaling of the hydraulic actuation system is unlikely to be effected by deployment.

Is it a known fact that deployment is by hydraulics? 

I question that assumption because the deployment does not look like it is done with hydraulics, & if it is hydraulic, it appears to be an unreliable system when you look at the uneven & unrepeatable deployment.  (see my video links a few posts back)

Why does it matter in regards to the thread topic "CRS-16 Discussion"?  If it is done with pneumatics ( or springs), it means that ground testing, or testing on the pad as part of the preflight, may not be possible.  This is where the weight of the Ti grid fins matters if you want to test under 1g, and it addresses the previous discussion of what solutions are possible to fix the failure mode.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: zubenelgenubi on 01/13/2019 07:51 am
Re: CRS-16 splashdown and return to port at nearly the same time as...
Iridium Next Flight 8 1st stage return to port:

Are both assets returning to the same dock or dock area?  If so, might they be there simultaneously?
That would be a great photo-op!
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Joey S-IVB on 01/13/2019 11:00 pm
As Chris mentioned in the updates section, is this the first night-time splashdown? I can't remember a previous SpaceX night splashdown.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ejb749 on 01/14/2019 04:22 am
The last line in the article should really say:

CRS-17 is the next Dragon ONE mission to the ISS, currently scheduled for March.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: ugordan on 01/14/2019 07:48 am
The last line in the article should really say:

CRS-17 is the next Dragon ONE mission to the ISS, currently scheduled for March.

I like your optimism.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Rondaz on 01/14/2019 03:57 pm
Dragon Back on Earth as Crew Revs Up Station Science

Mark Garcia Posted on January 14, 2019

The SpaceX Dragon cargo craft is back on Earth after splashing down in the Pacific Ocean Sunday night loaded with critical space research and International Space Station hardware. Four spaceships remain parked at the orbital lab including Northrop Grumman’s Cygnus resupply ship from the United States.

Today, the three-member Expedition 58 crew is exploring a wide array of microgravity science to improve life for humans on Earth and in space. The orbital residents also worked on life support systems and upgraded computer hardware.

NASA astronaut Anne McClain set up a specialized microscope in the morning for the Biophysics-5 study to research the production of protein crystals. Afterward, she deactivated Dragon communications gear then swapped out hard drives on several laptop computers.

Flight Engineer David Saint-Jacques of the Canadian Space Agency opened up the Combustion Integrated Rack and replaced optics gear inside the flame and soot research device. He later swapped a hydrogen sensor inside the Oxygen Generation System before inspecting and cleaning some of its parts.

A pair of tiny internal satellites, better known as SPHERES, were set up by Commander Oleg Kononenko today inside the Kibo laboratory module. High school students write algorithms and submit them in a competition to control the SPHERES to demonstrate spacecraft maneuvers and formation-flying for future space missions.

https://blogs.nasa.gov/spacestation/2019/01/14/dragon-back-on-earth-as-crew-revs-up-station-science/
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: tyrred on 01/15/2019 08:43 am
The last line in the article should really say:

CRS-17 is the next Dragon ONE mission to the ISS, currently scheduled for March.

I like your optimism.

Will DM-1 be the next splashdown for SpaceX?  Is CRS-16 the last Dragon1 splashdown before the first Dragon2 splashdown?  If so, what a sweet 16.

Edit: optimism
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: rpapo on 01/15/2019 10:34 am
Will DM-1 be the next splashdown for SpaceX?  Is CRS-16 the last Dragon1 splashdown before the first Dragon2 splashdown?  If so, what a sweet 16.
You need to add the two test flights plus the pad abort test, but then subtract CRS-7, which had a rather harder splashdown than usual.

So there have been 18 good splashdowns and one not so good so far.  Not counting the various parachute tests, of course.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: CorvusCorax on 01/15/2019 03:04 pm
Will DM-1 be the next splashdown for SpaceX?  Is CRS-16 the last Dragon1 splashdown before the first Dragon2 splashdown?  If so, what a sweet 16.
You need to add the two test flights plus the pad abort test, but then subtract CRS-7, which had a rather harder splashdown than usual.

So there have been 18 good splashdowns and one not so good so far.  Not counting the various parachute tests, of course.

yeah, I think even Dragon2 had a few splashdowns already, at least the parachute qualification test articles did ;)
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: zubenelgenubi on 01/15/2019 08:53 pm
Re: CRS-16 splashdown and return to port at nearly the same time as...
Iridium Next Flight 8 1st stage return to port:

Are both assets returning to the same dock or dock area?  If so, might they be there simultaneously?
That would be a great photo-op!

Tweet in NSF forum post here (https://forum.nasaspaceflight.com/index.php?topic=46944.msg1901628#msg1901628) contains video of such a view!
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: tyrred on 01/16/2019 08:42 am
Re: CRS-16 splashdown and return to port at nearly the same time as...
Iridium Next Flight 8 1st stage return to port:

Are both assets returning to the same dock or dock area?  If so, might they be there simultaneously?
That would be a great photo-op!

Tweet in NSF forum post here (https://forum.nasaspaceflight.com/index.php?topic=46944.msg1901628#msg1901628) contains video of such a view!

That is so nice  8)  Recovery and re-use is a lot sexier than expendable... Even if it gets dirty.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Comga on 01/18/2019 04:30 am
https://www.youtube.com/watch?v=mmfS-RJabzM (https://www.youtube.com/watch?v=mmfS-RJabzM)

Thinking about terminal docking maneuvers for DM-1 and DM-2, it appears that SpaceX was able to run a test of their lidar as the CRS-16 Dragon departed the ISS.

At ~1:25 in the video, just before the change of camera angles, the capsule disappears in front of the ISS.
Can anyone verify that this places the sensor and grapple fixture bay forward of and facing the IDA on the forward port of Node 2?
That would have enabled them to get some lidar returns from the docking aides inside and outside the contact ring.
It would be surprising that they could get usable data, and the normally insignificant offset between transmit and receive lenses becomes quite significant at such close range.
Title: Re: SpaceX Falcon 9 : CRS-16 (Dragon SpX-16) : December 5, 2018 - DISCUSSION
Post by: Swedish chef on 03/02/2019 08:30 am
In today's post flight press conference the hydraulic problem was described to have been caused by an valve. This valve was later redesigned and there was no need for an extra hydraulic pump.