NASA, SpaceX agree on space station flight

In message
Jeff Findley wrote:

From what I can tell, Dragon will be
grappled by the SSRMS and berthed to a CBM port on an MPLM. So Dragon
has to hold still enough to be grabbed.

This is the same sort of operation that the Japanese H-2 Transfer
Vehicle (HTV) performed back in 2009, so it's not going to be a "first".
But if it's successful, this should be huge news for the US spacecraft
industry.

Errr, why? Other than the arm being on the passive vehicle rather than
the active one, surely it's no different to any of the Hubble servicing
missions or any other time the shuttle went up to park next to something
else and grab it with the arm.

Anthony

In article , says...

In message
Jeff Findley wrote:

From what I can tell, Dragon will be
grappled by the SSRMS and berthed to a CBM port on an MPLM. So Dragon
has to hold still enough to be grabbed.

This is the same sort of operation that the Japanese H-2 Transfer
Vehicle (HTV) performed back in 2009, so it's not going to be a "first".
But if it's successful, this should be huge news for the US spacecraft
industry.

Errr, why? Other than the arm being on the passive vehicle rather than
the active one, surely it's no different to any of the Hubble servicing
missions or any other time the shuttle went up to park next to something
else and grab it with the arm.

Because with Hubble, the shuttle crew controlled both the rendezvous
*and* the grapple. Hubble has no reaction control system. It can only
control its orientation (which it does with great precision).

With Dragon, there is no crew on board to control the rendezvous.
Automated rendezvous of this type isn't trivial. Remember the
Progress/Mir collision? I'm sure no one wants a repeat of that accident
with ISS.

Jeff
--
" Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry
Spencer 1/28/2011

On Thu, 28 Jul 2011 13:48:23 -0400, Jeff Findley
wrote:

With Dragon, there is no crew on board to control the rendezvous.
Automated rendezvous of this type isn't trivial. Remember the
Progress/Mir collision? I'm sure no one wants a repeat of that accident
with ISS.

The Progress/Mir collision was while Progress was being remotely
piloted from Mir, not automated.

But agreed, this isn't trivial and success here will be huge.

Brian

"Jeff Findley" wrote in message
...
In article , says...

In message
Jeff Findley wrote:

From what I can tell, Dragon will be
grappled by the SSRMS and berthed to a CBM port on an MPLM. So
Dragon
has to hold still enough to be grabbed.

This is the same sort of operation that the Japanese H-2 Transfer
Vehicle (HTV) performed back in 2009, so it's not going to be a
"first".
But if it's successful, this should be huge news for the US
spacecraft
industry.

Errr, why? Other than the arm being on the passive vehicle rather than
the active one, surely it's no different to any of the Hubble servicing
missions or any other time the shuttle went up to park next to something
else and grab it with the arm.

Because with Hubble, the shuttle crew controlled both the rendezvous
*and* the grapple. Hubble has no reaction control system. It can only
control its orientation (which it does with great precision).

With Dragon, there is no crew on board to control the rendezvous.
Automated rendezvous of this type isn't trivial. Remember the
Progress/Mir collision? I'm sure no one wants a repeat of that accident
with ISS.

Jeff

True that. This is a big step, and I do wish them well on this one. If they
succeed, that brings commercial cargo a big step forward, and puts Space X
closer to commercial crew. I don't worship Musk or his company, but the
accolades for a successful flight will be well deserved.

Jeff Findley writes:

Because with Hubble, the shuttle crew controlled both the rendezvous
*and* the grapple. Hubble has no reaction control system. It can only
control its orientation (which it does with great precision).

With Dragon, there is no crew on board to control the rendezvous.
Automated rendezvous of this type isn't trivial. Remember the
Progress/Mir collision? I'm sure no one wants a repeat of that accident
with ISS.

The point is that this mission is just two missions folded into one.
Previously NASA wanted SpaceX to fly one mission in which Dragon would
fly several "virtual" approaches to the ISS in safe distance only and
then in a second mission actually repeat the same with the real thing.
Now SpaceX will do the first mission first and when this works out fine,
go to the ISS and berth there within the same flight.

So: Before this Dragon comes near the ISS it will have done all of what
it will do there in a safe distance. If anything goes wrong then it will
*not* come near the ISS and reenter instead.

It's surely not the easiest thing to do, but it looks as if this has
been planned well.


Jochem

--
"A designer knows he has arrived at perfection not when there is no
longer anything to add, but when there is no longer anything to take away."
- Antoine de Saint-Exupery

In article , says...

The point is that this mission is just two missions folded into one.
Previously NASA wanted SpaceX to fly one mission in which Dragon would
fly several "virtual" approaches to the ISS in safe distance only and
then in a second mission actually repeat the same with the real thing.
Now SpaceX will do the first mission first and when this works out fine,
go to the ISS and berth there within the same flight.

So: Before this Dragon comes near the ISS it will have done all of what
it will do there in a safe distance. If anything goes wrong then it will
*not* come near the ISS and reenter instead.

It's surely not the easiest thing to do, but it looks as if this has
been planned well.

Agreed. If NASA gave them the green light to combine the two missions
into one, they must have some confidence in SpaceX and Dragon.

Jeff
--
" Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry
Spencer 1/28/2011

On 7/28/2011 8:14 PM, Matt Wiser wrote:

True that. This is a big step, and I do wish them well on this one. If they
succeed, that brings commercial cargo a big step forward, and puts Space X
closer to commercial crew. I don't worship Musk or his company, but the
accolades for a successful flight will be well deserved.

Since ATV and HTV were allowed to berth at the ISS on their first
flights, I think it was hard for NASA to argue that Dragon couldn't.

Pat

On 7/29/2011 1:20 AM, Jochem Huhmann wrote:

So: Before this Dragon comes near the ISS it will have done all of what
it will do there in a safe distance. If anything goes wrong then it will
*not* come near the ISS and reenter instead.

It's surely not the easiest thing to do, but it looks as if this has
been planned well.

Yeah, it seems a pretty safe way of doing things.

Pat