[AR] Re: Falcon 9 flight today
- From: <johndom@xxxxxxxxx>
- To: <arocket@xxxxxxxxxxxxx>
- Date: Tue, 1 Oct 2013 16:36:42 +0200
http://www.youtube.com/watch?v=Zj0851Wkm9c
Nice clip showing 1D turbine exhaust.
jd
_____
Van: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx]
Namens JMKrell@xxxxxxx
Verzonden: maandag 30 september 2013 4:04
Aan: arocket@xxxxxxxxxxxxx
Onderwerp: [AR] Re: Falcon 9 flight today
I've been studying the Falcon 9r turbine exhaust port pattern. The
peripheral engine exhaust ports were moved inboard, the center engine
turbine exhaust is next to the engine and appears to have a collar, which
could be a deflector for roll control. Yes, it is only my supposition, but
that is how I would design the system for roll control. It is an easy
modification and carries a lower weight penalty than cold gas without a
reaction time limit in the event maximum design limits are exceeded.
Flipping the stage and settling the propellants would be a good application
for cold gas.
John Krell
In a message dated 9/29/2013 5:38:48 P.M. Pacific Daylight Time,
wikkit@xxxxxxxxx writes:
They said they had cold gas. They had to in order to flip the stage
before relighting to do the braking burn, and to settle propellants.
The gimbals are hydraulic, so presumably they could lock all of the
non-restarting engines
in place just before shutting them down.
They said they only recovered pieces; unless the engine bay had some
big water-activated flotation it seems like ~9000lb of engines is the
least likely part for them to have gotten back. The ocean is 12-14kft
deep where the boats are wandering around.
This is why I really like two engines for vertical landing. It's handy
to have far more roll control authority than you need without it
costing you a bunch of dead weight in attitude control system.
Ben
On Sun, Sep 29, 2013 at 6:20 PM, Lars Osborne <lars.osborne@xxxxxxxxx>
wrote:
> Peter is correct, there is no turbine exhaust for roll control on the M1D.
>
>
(https://lh5.googleusercontent.com/-WjOnSd0I1bc/UcygKKf6EHI/AAAAAAAAPyk/7o2y
HsQ9TJg/w1017-h848-no/shiny+merlin.jpg)
>
> I have no idea what they are doing for first stage ACS. Perhaps they had
> none for this one, and may use aerodynamic control surfaces on the legs in
> the future.
>
> Thanks,
> Lars Osborne
>
>
> On Sun, Sep 29, 2013 at 5:06 PM, Peter Yu <peterxyu@xxxxxxxxx> wrote:
>>
>> If I'm not mistaken, the Merlin 1Ds don't have turbine exhaust vectoring.
>> There's only ACS (could be cold gas thrusters or Draco).
>>
>>
>> On Sun, Sep 29, 2013 at 4:37 PM, <JMKrell@xxxxxxx> wrote:
>>>
>>> Peripheral engine symmetry is critical for roll control in a single
>>> engine landing. Control arm breakage or an engine position shift during
>>> engine forward reentry could be disastrous.
>>>
>>> John Krell
>>>
>>>
>>> In a message dated 9/29/2013 3:35:14 P.M. Pacific Daylight Time,
>>> ianmga@xxxxxxxxx writes:
>>>
>>> Yes
>>>
>>> On Sun, Sep 29, 2013 at 3:26 PM, <JMKrell@xxxxxxx> wrote:
>>> > The aerodynamic roll forces on the first stage exceeded the turbine
>>> > exhaust
>>> > to control roll. The F9r is a different beast from the Grasshopper.
>>> >
>>> > John Krell
>>> >
>>> > In a message dated 9/29/2013 3:00:20 P.M. Pacific Daylight Time,
>>> > ianmga@xxxxxxxxx writes:
>>> >
>>> > This was IMHO the most likely failure mode. An empty first stage is
>>> > stable engine forward in pitch and yaw but it's impossible to control
>>> > the roll torques due to the engines. Ok, it's not impossible, just
>>> > very difficult to model and hence to control. I am sure SpaceX knew
>>> > this and tried to solve it, but it was the only part of the whole
>>> > flightback that's truly challenging, hence most likely to fail. And it
>>> > did. They are however in the unique position of having good data on
>>> > engine first reentry. Nobody else does! So they'll be trying and
>>> > refining their models until they succeed sooner or later. Very
>>> > exciting. Wow.
>>> >
>>> > I strongly suspect this issue is one if not the main reason why the
>>> > Blue Origin 1st stage has fins. That'd be the cleanest way to do it.
>>> >
>>> > ian
>>> >
>>> > On Sun, Sep 29, 2013 at 1:49 PM, Henry Vanderbilt
>>> > <hvanderbilt@xxxxxxxxxxxxxx> wrote:
>>> >>
>>> >>
>>> >>
http://www.parabolicarc.com/2013/09/29/falcon-9-launch-payloads-orbit-vanden
berg/
>>> >> says the initial 3-engine relight and decel worked, the second
>>> >> low-altitude
>>> >> single-engine relight had problems, the stage then hit the water hard
>>> >> and
>>> >> was destroyed, but at least some of it was recovered. More details in
>>> >> the
>>> >> comments also.
>>> >>
>>> >> Henry
>>> >>
>>> >>
>>> >> On 9/29/2013 12:15 PM, Paul Mueller wrote:
>>> >>>
>>> >>> Congrats to SpaceX on what looked like a flawless flight of the
>>> >>> upgraded
>>> >>> F9 today! Has anyone heard anything about the 1st stage recovery
>>> >>> efforts?
>>> >>>
>>> >>> Paul M
>>> >>
>>> >>
>>> >
>>> >
>>> >
>>> > --
>>> > Ian M Garcia
>>> >
>>>
>>>
>>>
>>> --
>>> Ian M Garcia
>>>
>>
>
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