SpaceX launch and landing attempt scheduled for Sunday

SpaceX launch (Orbcom mission to deploy several satellites) is scheduled
to take place this Sunday. This is the V 1.2 version of Falcon 9 which
features increased performance from the Merlin engines, partially
facilitated by sub-cooled LOX (near its freezing point) and cooled
kerosene (to 20 degrees F).

Also, this will be the first landing attempt on land. The landing
attempt will take place at a former launch pad at Cape Canaveral Air
Force Station that SpaceX has converted into a landing facility (by
adding several circular concrete pads).

If the launch and the landing are both successful, this will be huge for
SpaceX.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer

On 12/19/15 8:49 PM, Fred J. McCall wrote :
Jeff Findley wrote:

SpaceX launch (Orbcom mission to deploy several satellites) is scheduled
to take place this Sunday. This is the V 1.2 version of Falcon 9 which
features increased performance from the Merlin engines, partially
facilitated by sub-cooled LOX (near its freezing point) and cooled
kerosene (to 20 degrees F).

Also, this will be the first landing attempt on land. The landing
attempt will take place at a former launch pad at Cape Canaveral Air
Force Station that SpaceX has converted into a landing facility (by
adding several circular concrete pads).

If the launch and the landing are both successful, this will be huge for
SpaceX.


I think what SpaceX was trying to do as an intermediate step (landing
on a barge) is actually harder than the next step (return to launch
and land on a pad). I hope this works so they can certify bringing it
back to an active launch site.

I agree. I think SpaceX knew this all along. I don't think they
considered the barge landing as an intermediate step in the sense that
it was easier to do. I think they tried landing on a barge at first
because it was safer.


Alain Fournier

In article ,
says...

I think what SpaceX was trying to do as an intermediate step (landing
on a barge) is actually harder than the next step (return to launch
and land on a pad). I hope this works so they can certify bringing it
back to an active launch site.

Agreed. Landing on a stationary concrete landing pad should be easier
than a floating, bobbing, moving barge on the ocean. Still, I give them
a 50/50 chance of a successful landing. This is, after all, still very
much a test program.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer

In article , says...

On 12/19/15 8:49 PM, Fred J. McCall wrote :

I think what SpaceX was trying to do as an intermediate step (landing
on a barge) is actually harder than the next step (return to launch
and land on a pad). I hope this works so they can certify bringing it
back to an active launch site.

I agree. I think SpaceX knew this all along. I don't think they
considered the barge landing as an intermediate step in the sense that
it was easier to do. I think they tried landing on a barge at first
because it was safer.

More importantly, because government regulators and Air Force range
safety officers thought it was safer. In reality, a returning, nearly
empty, Falcon 9 first stage is *much* less of a danger than a fully
fueled Falcon 9 first and second stage just clearing the tower. For
example, note the extensive damage to the pad when one of the Antares
engines failed shortly after lift-off. Now that was a bad day.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer

On 12/19/15 11:20 PM, Jeff Findley wrote :
In article , says...

On 12/19/15 8:49 PM, Fred J. McCall wrote :

I think what SpaceX was trying to do as an intermediate step (landing
on a barge) is actually harder than the next step (return to launch
and land on a pad). I hope this works so they can certify bringing it
back to an active launch site.

I agree. I think SpaceX knew this all along. I don't think they
considered the barge landing as an intermediate step in the sense that
it was easier to do. I think they tried landing on a barge at first
because it was safer.

More importantly, because government regulators and Air Force range
safety officers thought it was safer. In reality, a returning, nearly
empty, Falcon 9 first stage is *much* less of a danger than a fully
fueled Falcon 9 first and second stage just clearing the tower. For
example, note the extensive damage to the pad when one of the Antares
engines failed shortly after lift-off. Now that was a bad day.

I don't think I would say that: "a returning nearly empty Falcon 9 first
stage is much less of a danger than a fully fuelled Falcon 9 first and
second stage just clearing the tower". There is no doubt that the fully
loaded rocket is *much* more energetic and can make a bigger bang. But
it is outgoing, the returning vehicle is incoming. Unless there is a
problem with the autodestruct, the departing rocket won't do much damage
to anything but the launch tower and the ocean. The returning rocket
will do a much smaller bang but you don't know where, therefore you
can't really clear the area of humans or valuable assets. The two cases
offer very different kinds of dangers.

I'm not saying that it shouldn't be done, that it is too dangerous or
anything of the kind. Just like I'm not saying that rocket launches are
too dangerous and shouldn't be done. I'm a fan of vertical landing à la
SpaceX. But one should be aware that there are some risks, even if these
are small, and try to mitigate those risks.


Alain Fournier

In article om,
says...

On 2015-12-19 20:49, Fred J. McCall wrote:

I think what SpaceX was trying to do as an intermediate step (landing
on a barge) is actually harder than the next step (return to launch
and land on a pad).


I know that barge *appears* harder.

However, from the rocket's point of view, is there a difference ?

Yes, because the barge isn't completely stationary and the Falcon 9
first stage can't hover. It has one shot at getting its vertical
velocity to be zero when it touches the ground or the barge. If this
fails, and the engine keeps thrusting, the stage will go up.

Since the barge is moving it is indeed harder to insure that the
vertical velocity is zero when it touches the barge.

I am guessing that on ground, they may be able to give the software
some
more leaway to focus on landing instead of steering to the middle of the
X, as long as the landing is within x metres of the X. So at the last
minute, the rocket need not correct cross wind effects and just focus on
landing.

Having a bigger target is a good thing.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer

:-) :-) :-) :-) :-) :-) :-) :-) :-)

Great!


Alain Fournier

In article , says...

:-) :-) :-) :-) :-) :-) :-) :-) :-)

Great!


Alain Fournier

And the launch of the 11 Orbcomm satellites appears to have gone well
too. So happy customer, and happy SpaceX employees.

I was not able to watch it live, but watched the landing a couple of
times on the TV already (Chromecast is a great thing). First stage
landing is at about 42:00 in this video:

https://www.youtube.com/watch?v=O5bTbVbe4e4


Awesome job! That landing looked picture perfect to me.

I remember the days of DC-X discussions in sci.space and thought this
day would never come after the X-33 program failure.

SpaceX has done what the US government has never been able to do via
cost-plus contracts, which is recover a liquid fueled first stage intact
very near the launch site. This is heads and shoulders above dunking an
SRB in the ocean (submersion in salt water is typically not good for
aerospace hardware). And it's actually flying, which NASA's X-33
"winner" never did.

Yea, I'm rambling. This day will go down in history! Well, space
history anyway. :-)

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer

In article om,
says...

On 2015-12-21 03:25, Fred J. McCall wrote:

The difference being that those 'coordinates' change for a floating
platform.



Isn't that why they have station keeping thrusters on the barge to keep
barge stable ?


At what point must barge stop moving ? Rocket at 1000 m ? 100 m ? 10, 1m ?


When rocket is high enough, I assume it can easily "follow" the barge
movements and adjust trajectory, correct ?

It can't throttle its engine can't down enough to hover. The empirical
data suggests that that the stage simply does not have enough control
authority to easily do what you are suggesting. It has *one* chance at
landing at the correct location at zero velocity. Any variables which
interfere with this decrease the likelihood of a safe landing.

Also, the size of the landing area is surely a factor too. It would not
surprise me if the main concrete landing pad at landing facility 1 is
far larger than the barge. Because of this, allowing the horizontal
position to drift a bit in order to keep the attitude of the stage
perfectly vertical would be easier at LF1 than on the barge.

BTW, what surprised me of today's landing was how fast the rocket comes in.

That's because it can't hover. Again, it has *one* shot at this.

This is similar to the one shot that a space shuttle landing always had.
Because the shuttle was a glider, it could not "go around" and attempt
another landing if the first approach was bad. This was a criticism of
the vehicle as it limited the times and locations for landing (e.g. many
times, the orbiter would spend a few extra days in orbit waiting for the
weather at KSC to clear). But, this approach worked for the shuttle.


Will SpaceX ever "stick" a barge landing? I think they will,
eventually, but it will always be more risky and subject to sea
conditions. Greater wind speeds and larger waves will absolutely make
any landing attempt harder. Also, the heavier the payload is, the
smaller the amount of fuel is for a landing attempt. For heavier Falcon
9 payloads, the barge may still be needed.


Elon said yesterday that when Falcon Heavy starts flying, they'll need
the barge to recover the core stage since it will be flying higher and
faster at its stage separation than Falcon 9's first stage is at its
stage separation.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer

perhaps the rockets exhaust moves the bardge laning more difficult.

since a pad landing is easier and safer its not a problem,

get the stage back, inspect and refurb and fly again.

the lower costs by reusing boosters will make SLS look worse