Leaning tower of falcon 9

The LA Times is reporting today's landing attempt was unsuccessful:

SpaceX launches two satellites, but drone ship landing is unsuccessful.
http://www.latimes.com/business/la-f...nap-story.html

Elon Musk Verified account
�@elonmusk
Looks like thrust was low on 1 of 3 landing engines. High g landings v
sensitive to all engines operating at max.
https://twitter.com/elonmusk/status/743097337782763521

My opinion, in order to land successfully in a consistent fashion SpaceX
will have to give the F9 hovering ability.

High g landings are endemic to a "hover-slam" landing, more commonly
referred to as a "suicide-burn", more accurately referred to as "land or
slam", since without hovering ability, you only get one chance at it. You
either stick the landing on the first try, or you crash and burn.

Bob Clark


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nvalid...

In sci.space.policy message -
september.org, Mon, 6 Jun 2016 07:14:24, Jeff Findley
posted:

In article id,
says...

In sci.space.policy message -
september.org, Fri, 3 Jun 2016 15:48:38, Jeff Findley
posted:

3. Getting the thing vertical when the barge is moving in the ocean
would be "challenging".

I think not. One need only pump ballast within the barge in the
compensating direction. It is getting the thing perpendicular to the
deck that should be difficult.

You could do this, but I would think doing so would screw up the ability
for the tug to get it back to port in a timely fashion.

Many seagoing vessels have been towed to port, often in extreme
conditions, with very considerable lists. Even the "Flying Enterprise"
was nearly saved : https://en.wikipedia.org/wiki/SS_Flying_Enterprise.


Since the vast majority of the mass of an empty stage is at the bottom,
actual tilt is relatively unimportant.

In other words, "if it ain't broke, don't fix it". So what if it was
leaning? It made it back to port safely, which is what matters.

Yes; I was only challenging the 'would be "challenging"', not advocating
that it would be _useful_ to do it.


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In article ,
says...

The LA Times is reporting today's landing attempt was unsuccessful:

SpaceX launches two satellites, but drone ship landing is unsuccessful.
http://www.latimes.com/business/la-f...nap-story.html

Yes, but the launch *was* successful, so the paying customer is happy
and the Falcon flight program will continue. :-)

Elon Musk Verified account
?@elonmusk
Looks like thrust was low on 1 of 3 landing engines. High g landings v
sensitive to all engines operating at max.
https://twitter.com/elonmusk/status/743097337782763521

He also Tweeted that SpaceX has already been working on ways to handle
this situation. In other words, it's just like the launch that "ran out
of hydraulic fluid" for the grid fins. Even before that failure, they
were working on increasing the fluid available for landings.

My opinion, in order to land successfully in a consistent fashion
SpaceX will have to give the F9 hovering ability.

I respectfully disagree. Again, this is a known issue that was already
being worked on. This is a *test flight program*. SpaceX has yet to
even refly a stage! Problems are expected during a test flight program.
You develop fixes for problems as they become known. In this case, the
problem was already known and a fix was already in the works. This was
not an "unknown unknown" this time. It was a known risk that they took
in order to fly the mission for the customer without making them wait
for a landing fix they largely don't care about.

The customer just wants their satellites in the proper orbit. That
mission was accomplished.

High g landings are endemic to a "hover-slam" landing, more commonly
referred to as a "suicide-burn", more accurately referred to as "land or
slam", since without hovering ability, you only get one chance at it. You
either stick the landing on the first try, or you crash and burn.

You only got one chance at final approach and landing a shuttle orbiter,
but they were all successful (with arguably a few close calls). So
that, in and of itself, doesn't disqualify the hover slam approach.
Besides, the Falcon 9 first stage is unmanned, so nobody was killed.

Remember, "perfect is the enemy of good enough". If they can make this
"good enough", they can learn from it and incorporate all of the lessons
learned in their next generation vehicle. Not everything has to be
fixed in version 1.X of a vehicle. Version 1 just has to be "good
enough". Version 2.0 can contain major upgrades and will hopefully be
even better.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

Jeff Findley wrote:

In article ,
says...

The LA Times is reporting today's landing attempt was unsuccessful:

SpaceX launches two satellites, but drone ship landing is unsuccessful.
http://www.latimes.com/business/la-f...nap-story.html

Yes, but the launch *was* successful, so the paying customer is happy
and the Falcon flight program will continue. :-)


Right. And since right now he's charging as if he's not going to get
the stages back, SpaceX is also happy (enough).


Elon Musk Verified account
?@elonmusk
Looks like thrust was low on 1 of 3 landing engines. High g landings v
sensitive to all engines operating at max.
https://twitter.com/elonmusk/status/743097337782763521

He also Tweeted that SpaceX has already been working on ways to handle
this situation. In other words, it's just like the launch that "ran out
of hydraulic fluid" for the grid fins. Even before that failure, they
were working on increasing the fluid available for landings.


And even if they don't, if it works only part of the time they still
come out ahead as long as the cost of recovery and refurbishment is
lower than a new booster.

My opinion, in order to land successfully in a consistent fashion
SpaceX will have to give the F9 hovering ability.

I respectfully disagree. Again, this is a known issue that was already
being worked on. This is a *test flight program*. SpaceX has yet to
even refly a stage! Problems are expected during a test flight program.
You develop fixes for problems as they become known. In this case, the
problem was already known and a fix was already in the works. This was
not an "unknown unknown" this time. It was a known risk that they took
in order to fly the mission for the customer without making them wait
for a landing fix they largely don't care about.

The customer just wants their satellites in the proper orbit. That
mission was accomplished.


I agree with you. Not only would building in 'hover' for recovery
invalidate all the work they've already done (essentially start over
and crash some more until the landing software was right), but it
would require an expensive redesign of the engines. Since SpaceX can
already compete on price with the existing system, it's just not worth
the cost.

This is the problem with a lot of people who just think about 'theory'
and push for performance. They lose sight of the economics of the
thing.

High g landings are endemic to a "hover-slam" landing, more commonly
referred to as a "suicide-burn", more accurately referred to as "land or
slam", since without hovering ability, you only get one chance at it. You
either stick the landing on the first try, or you crash and burn.

You only got one chance at final approach and landing a shuttle orbiter,
but they were all successful (with arguably a few close calls). So
that, in and of itself, doesn't disqualify the hover slam approach.
Besides, the Falcon 9 first stage is unmanned, so nobody was killed.

Remember, "perfect is the enemy of good enough". If they can make this
"good enough", they can learn from it and incorporate all of the lessons
learned in their next generation vehicle. Not everything has to be
fixed in version 1.X of a vehicle. Version 1 just has to be "good
enough". Version 2.0 can contain major upgrades and will hopefully be
even better.


SpaceX essentially gets the recovered stages for 'free', since they
charge the customer as if the stage is going to be expended. There
are at least three different cost models that would allow SpaceX to
lower costs based on booster recovery. All of them work just fine
(given analysis of costs and recovery success rates) with an
'imperfect' percentage of successful recovery attempts.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

In article ,
says...

The LA Times is reporting today's landing attempt was unsuccessful:

SpaceX launches two satellites, but drone ship landing is unsuccessful.
http://www.latimes.com/business/la-f...nap-story.html

Elon Musk Verified account
?@elonmusk
Looks like thrust was low on 1 of 3 landing engines. High g landings v
sensitive to all engines operating at max.
https://twitter.com/elonmusk/status/743097337782763521

My opinion, in order to land successfully in a consistent fashion SpaceX
will have to give the F9 hovering ability.

SpaceX released a video showing how close this landing was. Apparantly
the stage ran out of LOX right above the deck. You'll want to take a
look because it actually looks very close to hovering in the video.

https://www.reddit.com/r/spacex/comm...on_twitter_loo
ks_like_early_liquid/

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.