SpaceX Falcon 9 - Iridium NEXT Flight 1 DISCUSSION (Jan. 14 2017)

[gongora]

Please stop this discussion of launching without a license.  It wouldn't happen and there is no need to waste any more time on it.

[Kansan52]

Getting back to the static firing, anyone know if this F9 was more heavily instrumented than usual?

No signs of that.

[wannamoonbase]

Here is the link the the license:

https://www.faa.gov/about/office_org/headquarters_offices/ast/licenses_permits/media/SpaceX%20LLS%2017-096%20License%20and%20Orders_01_06_2017.pdf

Interesting.  The license LLS 17-096B (Flight) in paragraph 3(e) authorizes

"Landing the Falcon 9 Version 1,2 first stage either on a droneship or in the ocean"

So, no FAA approval for RTLS landings at VAFB yet.

Doesn't mean that the RTLS can't be a minimum distance from shore.

[envy887]

Here is the link the the license:

https://www.faa.gov/about/office_org/headquarters_offices/ast/licenses_permits/media/SpaceX%20LLS%2017-096%20License%20and%20Orders_01_06_2017.pdf

Interesting.  The license LLS 17-096B (Flight) in paragraph 3(e) authorizes

"Landing the Falcon 9 Version 1,2 first stage either on a droneship or in the ocean"

So, no FAA approval for RTLS landings at VAFB yet.

Doesn't mean that the RTLS can't be a minimum distance from shore.

That depends on performance, for one thing. NASA's EELV performance page gives F9 FT RTLS payload to 680 km SSO as 8225 kg. There's some disagreement on whether these birds mass 800 or 860 kg each, but including the 1000 kg dispenser that's at least 9000 kg. Might be too heavy for RTLS with the current F9.

[yg1968]

For the static fire, was the payload matted to the rocket? I am guessing that it wasn't.

[DatUser14]

It was not

[Comga]

For the static fire, was the payload matted to the rocket? I am guessing that it wasn't.

Asked and answered....

[meekGee]

But for SpaceX, it's almost surely software.  The first stage is solving convex optimization in real time, a much harder task than yaw steering.

Not true.  Targeting for yaw steering is harder.  Again, the landing pad is a static target and always be in the same place no matter what time it is launched.  Launching into a specific orbital plane at anytime within a launch window is much harder.

Respectfully, I disagree. Landing is harder on the software. Margin for error is far, far smaller and control scheme is different, having to blend thrust and aero surfaces with real-time sensor data from radar.

Not saying yaw steering is a stroll in the park. But I cannot see it being a harder software challenge than barge landing.

Not to mention that landing needs to zero 6 degrees of freedom, plus their first derivatives....

And yeah, to a much finer tolerance...

And in the presence of strong disturbing forces, on a large body with a quickly diminishing amount of fuel in it.

[Jim]

Not saying yaw steering is a stroll in the park. But I cannot see it being a harder software challenge than barge landing.

It is harder.  Landing can occur at an launch time. Yaw steering has to take into account launch time and launch location.

Landing on a spot is no different than rendezvous and docking.

[meekGee]

Not saying yaw steering is a stroll in the park. But I cannot see it being a harder software challenge than barge landing.

It is harder.  Landing can occur at an launch time. Yaw steering has to take into account launch time and launch location.

Landing on a spot is no different than rendezvous and docking.

A docking spacecraft is in zero g and can take its time with the maneuver. You have all the authority you need, and can abort and try again.

An F9 doing a hoverslam is so completely a different thing.

It is decelerating at multiple g, in wind, with very limited controls, especially towards the end - mostly main engine gimbaling.

Not the same as docking

[dglow]

Landing on a spot is no different than rendezvous and docking.

Except for the timeframes involved, capacity for do-overs, opportunities to abort, and consequences to the vehicle. Other than than, the two are identical.

Which is 'harder' may ultimately be a subjective matter... and also OT for this thread, no?

[Jim]

A docking spacecraft is in zero g and can take its time with the maneuver. You have all the authority you need, and can abort and try again.

An F9 doing a hoverslam is so completely a different thing.

It is decelerating at multiple g, in wind, with very limited controls, especially towards the end - mostly main engine gimbaling.

Not the same as docking

wrong.  Avionics wise it is the same.  Landing just has more constraints and external influences.  The F9 always knows where it is going to land.   Landing a vehicle is not hard (see lunar and mars landers).   

Landing actually uses less external sensors (altitude radar).  Rendezvous and docking require long range (star trackers, radar, etc) and short range (radar, lidar, TV, etc) sensors. 

[meekGee]

The longer range bit for rough initial navigation is achieved by a combination of inertial navigation sensors and GPS instead of a star tracker.

It is also the easiest part of either problem and irrelevant to the difficulty.

The secret sauce of the reentry burn and the aerodynamic​ flight segment are unique to SpaceX and already more difficult.

The final hoverslam maneuver, compared to the final docking maneuver... I'm struggling to even come up with an analogy.

There is nothing more predictable than orbiting bodies. A tiny puff of thrust here and there from any of many control thrusters, a simple constant velocity coast, no rotation motions, and then mechanical capture...  And you have all he time in the world to look at the process and back off.

A falcon comes in, fighting the wind, using almost only the gimbalimg engine cluster for control, has to do a divert, everything happening at high velocity going down to zero within seconds, no chance of a do over...

Easier than docking?  Not even close.

Even if visiting vehicles would approach ISS at 100 m/s, and brake to a halt on its surface without bouncing off or being captured - it would still be easier than what SpaceX does.

[Jim]

The longer range bit for rough initial navigation is achieved by a combination of inertial navigation sensors and GPS instead of a star tracker.

wrong, star tracker is for tracking the target at long range

The secret sauce of the reentry burn and the aerodynamic​ flight segment are unique to SpaceX and already more difficult.

Doesn't require any changes to the avionics to perform those tasks.   Just a little more programming

And you have all he time in the world to look at the process and back off.

A falcon comes in, fighting the wind, using almost only the gimbalimg engine cluster for control, has to do a divert,

Meaningless.  Neither have no bearing on the avionics or flight software architecture, where as yaw steering and rendezvous/docking do. 

Landing can be done independent of the actual time, unlike yaw steering and rendezvous/docking.  That is a major change to the avionics/ flight software architecture

[Robotbeat]

How is yaw steering hard? You need more on board memory to store a look up table of launch solutions, but other than that, how is it hard? Particularly, how can it possibly be easier than landing?

Landing on a small platform with rockets, in atmosphere, and in Earth gravity is anything but easy.

[Jim]

How is yaw steering hard? You need more on board memory to store a look up table of launch solutions, but other than that, how is it hard? Particularly, how can it possibly be easier than landing?

Landing on a small platform with rockets, in atmosphere, and in Earth gravity is anything but easy.

Time reference

[oiorionsbelt]

  Landing a vehicle is not hard (see lunar and mars landers).     

How can this be? Mars landings are touted as one of the toughest feats out there. JPL gets lots of kudos for doing that. Lunar landings are still rare and booster landings are but one year old.
 if "Landing a vehicle is not hard" then we've been dicking around for a long time.

[Kaputnik]

Wanted to ask which vehicles can do yaw steering but thought it was better to start a new thread:
http://forum.nasaspaceflight.com/index.php?topic=41982.0

[Chris Bergin]

Great work by Kaputnik to start a splinter thread. Two more posts followed, they are merged into the new splinter thread. Some older posts can be copied (quoted) and posted into the new thread if you wish, but no more of it on this thread. Ta!

[Nick L]

Info not confirmed so I post this tweet here :
https://twitter.com/VincentLamigeon/status/817797297832501249

Edit/gongora: Tweet text is "#SpaceX return to flight will not occur on Monday 9th as planned. Officially weather issues. Jan 10th possible date, but pretty unlikely"
Edit : too fast gongora,  thanks