SpaceX Falcon 9 CRS/SpX-10 Dragon - Feb. 19, 2017 - Discussion

[douglas100]

Maybe the deorbit burn was to depletion and out of plane. They might be trying to get an accurate measurement of second stage performance. By burning out of plane they would reduce the possibility of the re-entry trajectory  being too steep and short if the remaining prop reserves were more than anticipated. The width of the exclusion zone could reflect uncertainty of the quantity of remaining prop in a worst case scenario.

[Danderman]

Maybe the deorbit burn was to depletion and out of plane. They might be trying to get an accurate measurement of second stage performance. By burning out of plane they would reduce the possibility of the re-entry trajectory  being too steep and short if the remaining prop reserves were more than anticipated. The width of the exclusion zone could reflect uncertainty of the quantity of remaining prop in a worst case scenario.

Does SpaceX have the capability of monitoring a re-entry burn on the other side of the planet?

What does it mean that the re-entry trajectory being too steep? What does "too steep" mean in this context?

Also, a burn out of plane would mean no re-entry if there was not sufficient prop.

[douglas100]

Maybe the deorbit burn was to depletion and out of plane. They might be trying to get an accurate measurement of second stage performance. By burning out of plane they would reduce the possibility of the re-entry trajectory  being too steep and short if the remaining prop reserves were more than anticipated. The width of the exclusion zone could reflect uncertainty of the quantity of remaining prop in a worst case scenario.

Does SpaceX have the capability of monitoring a re-entry burn on the other side of the planet?

TDRSS?

What does it mean that the re-entry trajectory being too steep? What does "too steep" mean in this context?

That the stage might fall short of the designated zone if the burn was longer than anticipated.

Also, a burn out of plane would mean no re-entry if there was not sufficient prop.

True. That would have to be factored into how far out of plane the burn would be.

[mtakala24]

In a worst case scenario, do we know how many berthing attempts the Dragon's fuel capacity can provide for, before having insufficient propellant left for a successful return to Earth?

I can't answer that, but would like to add to it- is it technically or procedurally possible to adjust the ISS's own position to make up for a shortfall in performance of a VV?

Yes, it is possible. There were real plans in case for a shuttle underperformance. It went by the name of "Join Underspeed Recovery", JURe. It was discussed at least here:

https://forum.nasaspaceflight.com/index.php?topic=6156.msg165806#msg165806

edit:
Just to add, I doubt any real plans exist for these commercial or Russian visiting vehicle launches. Shuttle was a special case.

[Jim]

Does SpaceX have the capability of monitoring a re-entry burn on the other side of the planet?

TDRSS?

Spacex doesn't use TDRSS.  There are two USN stations on the Australian west coast and that's who Spacex uses.

[old_sellsword]

Does SpaceX have the capability of monitoring a re-entry burn on the other side of the planet?

TDRSS?

Spacex doesn't use TDRSS.  There are two USN stations on the Australian west coast and that's who Spacex uses.

Not even for Dragon?

45 seconds into this video, an avionics intern says otherwise.

[Jim]

Does SpaceX have the capability of monitoring a re-entry burn on the other side of the planet?

TDRSS?

Spacex doesn't use TDRSS.  There are two USN stations on the Australian west coast and that's who Spacex uses.

Not even for Dragon?

45 seconds into this video, an avionics intern says otherwise.
https://www.youtube.com/watch?v=wEduiMyl0ko?t=45s

We are talking about the Falcon

[zubenelgenubi]

Following up on my question earlier in this thread:

What are the ISS program constraints on this Dragon launch?

There's a small high-beta angle docking/berthing cut-out Feb. 21-24.
<snip>

Currently, a Dragon launch on the 18th puts capture and berthing on the 20th.

In case of further launch delay, would the launch be delayed to the 23rd, placing capture and berthing on the 25th, after a 2-day ISS rendezvous?

Or would the launch occur on the next day that ISS orbital mechanics allow, Dragon would pursue a 2 days rendezvous with the station, and then loiter a few kilometers away from ISS until the high-beta angle cut-out is over?

Or, are there other options, such as a 3 or more day rendezvous?

Can the high-beta angle cut-out be whittled down via analysis?

There was some interesting information and discussion that followed this post on this thread--thank you, NSF members!

To my knowledge, my question regarding capture and berthing during the high-beta angle cut-out was not answered.  What was the solution?

(Launch occurred on 2/19 UTC.  Capture and berthing occurred on 2/23 UTC, within the cut-out.)

Thank you.

[Raul]

I've got a question about the second stage reentry.  In the launch updates thread, these two reentry map images were posted (click the quote links to see the images):

This was from Raul's hazard map.  If you zoom out far enough to see Australia, you'll see the re-entry hazard zone for the upper stage.  I have seen no information on the accuracy of the actual reentry.  This was just the planned area.

Something like this orbit

The first is the NOTAM map showing a region extending down to 61 deg South.

The second is the ISS orbital track showing paths down to the nominal 51.6 deg South.  The thing is, that reentry is NOT something like that orbit, for reasonable values of "something"

Why was the reentry zone planned for so much further south than the orbital track?  10 degrees of inclination is nothing to sneeze at.  Was SpaceX doing a delta-V / plane-change test with their second stage, after Dragon sep?

I agree that without a maneuver, the impact zone should not extend south of the southernmost ground track.  A back of the envelope calculation makes a maneuver look possible.  To change orbital plane by 10 degrees will take something like 1000 m/s of delta V.  But the second stage is quite light after separating from Dragon, something like 5000 kg.  Given the vacuum thrust of 911kn, that's something like 182 m/s (18G) acceleration.   So only a 5-6 second burn would be required, and it's certainly possible they had that type of reserves.

What I additionally found, there were several little confusing modifications of S2 debris area.

Launch date 18 Feb, alternatively 19 Feb:
HYDROPAC 528/2017 - 13 Feb 04:01 UTC - bounded area with higher then ISS inclination
HYDROPAC 556/2017 - 15 Feb 20:45 UTC - area within 150 miles of trackline joining - with higher then ISS inclination
HYDROPAC 592/2017 - 17 Feb 17:32 UTC - bounded area with ISS inclination - consistent with observed groundtrack.

Launch date 19 Feb, alternatively 21 Feb:
HYDROPAC 601/2017 - 18 Feb 16:02 UTC - bounded area with ISS inclination
HYDROPAC 602/2017 - 18 Feb 18:42 UTC - again area within 150 miles of trackline joining - still with higher then ISS inclination
HYDROPAC 608/2017 - 19 Feb 16:28 UTC - HYDROPAC 602/17 operations completed
HYDROPAC 609/2017 - 19 Feb 16:38 UTC - HYDROPAC 601/17 operations completed

So we have two areas and one trackline with two different inclinations. Because area with ISS inclination is consistent with observed groundtrack over Saudi Arabia, other area could be wrong or alternative in case of plane change maneuver, which probably wasn't performed.

[fatdeeman]

I don't think anyone posted this yet, poor quality technically but gives a graphic sense of how fast the stage is still moving close to touchdown.

[Ronpur50]

Did we ever find out when the 1st stage was moved from LZ-1?  I spotted the transporter at pad 39A on Wednesday, so I wondered if it had already been moved.

[Lar]

In a worst case scenario, do we know how many berthing attempts the Dragon's fuel capacity can provide for, before having insufficient propellant left for a successful return to Earth?

I can't answer that, but would like to add to it- is it technically or procedurally possible to adjust the ISS's own position to make up for a shortfall in performance of a VV?

Yes, it is possible. There were real plans in case for a shuttle underperformance. It went by the name of "Join Underspeed Recovery", JURe. It was discussed at least here:

https://forum.nasaspaceflight.com/index.php?topic=6156.msg165806#msg165806

edit:
Just to add, I doubt any real plans exist for these commercial or Russian visiting vehicle launches. Shuttle was a special case.

It has to be possible, but it's kind of just as silly as the supertanker maneuvering because the mail boat can't quite make it close enough. such a big contrast in fuel usage to move ISS instead of Dragon....

[AS-503]

Not sure that this has been posted for this flight already.
Flight Club has visually modeled the launch and landing trajectory of several SpaceX missions.
The link below is for CRS-10.
Impressive visuals, particularly the plots on the right side of the screen!

[Ben the Space Brit]

In a worst case scenario, do we know how many berthing attempts the Dragon's fuel capacity can provide for, before having insufficient propellant left for a successful return to Earth?

I may be wrong but I think Dragon starts out in an parallel intercept orbit with the same period but different perigee and apogee that leads it to observationally appear to be orbiting the ISS. All orbits change over a period of months and years. Manoeuvring burns are needed for the Dragon to pull out of the 'racetrack' into a slow approach to the station.

[Comga]

In a worst case scenario, do we know how many berthing attempts the Dragon's fuel capacity can provide for, before having insufficient propellant left for a successful return to Earth?

I may be wrong but I think Dragon starts out in an parallel intercept orbit with the same period but different perigee and apogee that leads it to observationally appear to be orbiting the ISS. All orbits change over a period of months and years. Manoeuvring burns are needed for the Dragon to pull out of the 'racetrack' into a slow approach to the station.

That's not how it's done. 
That would require additional phasing on the part of the ISS, among other problems.
Dragon is launched into a coplanar lower orbit with a shorter period.  It "catches up" to the ISS.
Your idea about an "orbit with the same period but different perigee and apogee" is what happened to the Dragon after the approach abort.   It does then "appear to be orbiting the ISS", going around once per orbit.

[ChrisC]

Here's a timelapse video of the STP-H5 installation by Spaceflight101:
https://www.youtube.com/watch?v=stQvMaz-5gY

Published on 3 Mar 2017:  Sped-up video from the International Space Station showing robotic activity from February 26 through 28, covering the removal of the STP-H5 payload pallet from the Trunk Section of the Dragon SpX-10 spacecraft, the removal & temp-stowage of the OPALS payload and the installation of STP-H5 in OPAL's place on Express Logistics Carrier 1.

This is a fantastic video, and worth sharing on social media.  Play it at double speed (via settings / gear symbol in lower right corner) to move things along at a brisk clip.  Absolutely gorgeous shots, and provides the Regular Joe with a peek into what's going on over our heads.

[macpacheco]

In a worst case scenario, do we know how many berthing attempts the Dragon's fuel capacity can provide for, before having insufficient propellant left for a successful return to Earth?

Consider Dragon arrives at the 500 meters distance to ISS. If it then moved at 1m/s directly it would take just 5 minutes to arrive.
Approach speeds are likely in the 0.2m/s range (just an educated guess). That means nearly inconsequential fuel requirements even considering all the intermediary start/stops along the way.
I recall from memory the Dragon de orbit burn is 100m/s.
I would be really surprised if Dragon doesn't have enough hydrazine for ten attempts at normal speeds.
Additional consideration, if fuel were short, Dragon could use even slower speeds to save fuel. Let the approach take 2 hours.
Of course that's just a poorly educated guess.

[Comga]

In a worst case scenario, do we know how many berthing attempts the Dragon's fuel capacity can provide for, before having insufficient propellant left for a successful return to Earth?

Consider Dragon arrives at the 500 meters distance to ISS. If it then moved at 1m/s directly it would take just 5 minutes to arrive.
Approach speeds are likely in the 0.2m/s range (just an educated guess). That means nearly inconsequential fuel requirements even considering all the intermediary start/stops along the way.
I recall from memory the Dragon de orbit burn is 100m/s.
I would be really surprised if Dragon doesn't have enough hydrazine for ten attempts at normal speeds.
Additional consideration, if fuel were short, Dragon could use even slower speeds to save fuel. Let the approach take 2 hours.
Of course that's just a poorly educated guess.

Any attempt to do linear calculations on orbital maneuvers is futile.  NOTHING up there works like that.
Plus we can safely assume that the biggest limitation is not fuel.  The abort started a procedure for another attempt the next day, 24 hours out.  They will run out of time and patience long before they run out of fuel.

[macpacheco]

In a worst case scenario, do we know how many berthing attempts the Dragon's fuel capacity can provide for, before having insufficient propellant left for a successful return to Earth?

Consider Dragon arrives at the 500 meters distance to ISS. If it then moved at 1m/s directly it would take just 5 minutes to arrive.
Approach speeds are likely in the 0.2m/s range (just an educated guess). That means nearly inconsequential fuel requirements even considering all the intermediary start/stops along the way.
I recall from memory the Dragon de orbit burn is 100m/s.
I would be really surprised if Dragon doesn't have enough hydrazine for ten attempts at normal speeds.
Additional consideration, if fuel were short, Dragon could use even slower speeds to save fuel. Let the approach take 2 hours.
Of course that's just a poorly educated guess.

Any attempt to do linear calculations on orbital maneuvers is futile.  NOTHING up there works like that.
Plus we can safely assume that the biggest limitation is not fuel.  The abort started a procedure for another attempt the next day, 24 hours out.  They will run out of time and patience long before they run out of fuel.

Are my assumptions about fuel consumption actually wrong or you're just pointing out that other resources / limits would run out before they make that many approach attempts (which I agree with) ? I would appreciate a more educational answer rather than to censure the non rocket engineer trying to thing. After all I did say it was a poorly educated guess.
Yes, the bottom line is there's an implicit assumption that such problems won't repeat themselves consecutive times. They should be really rare such that even single approach problems would happen less than 10% of the time. But that wasn't the question.

[Comga]

The answer to all of your questions is yes
The math is not extremely high level, but it's not linear. You can't divide distance by time to get velocity. All velocities are perturbations to the ~7 km/sec orbital velocity and everything rotates every orbit.
Yes there are other considerations
I don't know the fuel capacity and total delta-V capability. While some here do, that's not the limit.
But like the wise owl in the 1960's Tootsie Pop ad, our answer to your initial question is "two" 😉