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Dragon2 test flight



 
 
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  #1  
Old March 2nd 19, 10:17 AM posted to sci.space.policy
Rocket Man
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Posts: 23
Default Dragon2 test flight


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

"JF Mezei" wrote in message
...
Saw an animation of the upcoming Fragon 2 test flight and it included
docking to the station.

Has NASA changed its policy that the first test flight nears the
station
but doesn't get t touch it?

Or have they agreed to let it do the "no touch" test flight and if that
works, then allow it to dock?

Since this is first Dragon flight docking at the modified PMA2 with
totally new guidance/navigation to it, what special steps would be
taken?

Being crewless, will this be totally automated, or will the ISS crew
use
the SpaceX equivalent to the Toru manual remote control ?


I read that the Russians are pretty nervous about Dragon2 since it
doesn't
have an independent backup computer system. If it fails the Dragon2
capsule
may beome uncontrollable and collide with the station. NASA has brushed
aside these concerns, I sure hope they know what they're doing.


From what I understand, Dragon 2 has a triply redundant computer system
so any computer hardware problem shouldn't be an issue. I'd bet the
updated computer hardware on Dragon 2 is at least somewhat based on what
was done with Dragon, which has been successful in terms of its software
used to approach and station keep near ISS so that the SSRMS can grab
it.


The difference is that Cargo Dragon is docked via a robotic arm, whilst Crew
Dragon docks via the airlock. That's a significant difference. Also, the
astronauts don't have any control over Crew Dragon, it's completely
autonomous. If something goes wrong, there's nothing they can do to prevent
a catastrophe.


  #2  
Old March 3rd 19, 10:06 AM posted to sci.space.policy
Niklas Holsti
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Posts: 168
Default Dragon2 test flight

On 19-03-02 11:17 , Rocket Man wrote:
"Jeff Findley" wrote in message
...

...
From what I understand, Dragon 2 has a triply redundant computer system
so any computer hardware problem shouldn't be an issue. [...]


[...] Also, the
astronauts don't have any control over Crew Dragon, it's completely
autonomous.


I believe that is not correct. At the pre-launch press conference it was
evident that the Crew Dragon can be commanded from the ISS -- as long as
the commanding system works, of course. The docking plan includes a
"back away" command sent from the ISS (or so I understood) which will
make the Crew Dragon move a certain distance away, and then a new
command will let it approach again, and dock.

If something goes wrong, there's nothing they can do to prevent
a catastrophe.


The risk is that the Crew Dragon malfunctions in a way that prevents
commanding it.

--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .
  #3  
Old March 3rd 19, 03:54 PM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 2,307
Default Dragon2 test flight

In article ,
says...

"Jeff Findley" wrote in message
...

From what I understand, Dragon 2 has a triply redundant computer system
so any computer hardware problem shouldn't be an issue. I'd bet the
updated computer hardware on Dragon 2 is at least somewhat based on what
was done with Dragon, which has been successful in terms of its software
used to approach and station keep near ISS so that the SSRMS can grab
it.


The difference is that Cargo Dragon is docked via a robotic arm, whilst Crew
Dragon docks via the airlock. That's a significant difference. Also, the
astronauts don't have any control over Crew Dragon, it's completely
autonomous. If something goes wrong, there's nothing they can do to prevent
a catastrophe.


I watched the docking on NASA TV this morning. The crew were definitely
monitoring the approach and even had a display from the Dragon 2 on one
of their laptops. Could they have commanded an abort from that laptop?
I don't know, but it wouldn't surprise me if they could command a hold
or even an abort.

The guy I know who would have known left NASA a few years ago.
Rendezvous and proximity operations software was what he did for NASA.

But certainly Dragon 2 could have been commanded to abort from the
ground. While Dragon 2 did dock autonomously, it was absolutely
monitored by both the ground and the crew on ISS and surely any sign of
something going wrong would have resulted in an abort command from a
human somewhere.

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.
  #4  
Old March 3rd 19, 08:32 PM posted to sci.space.policy
Niklas Holsti
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Posts: 168
Default Dragon2 test flight

On 19-03-03 16:54 , Jeff Findley wrote:
In article ,
says...

"Jeff Findley" wrote in message
...

From what I understand, Dragon 2 has a triply redundant computer system
so any computer hardware problem shouldn't be an issue. I'd bet the
updated computer hardware on Dragon 2 is at least somewhat based on what
was done with Dragon, which has been successful in terms of its software
used to approach and station keep near ISS so that the SSRMS can grab
it.


The difference is that Cargo Dragon is docked via a robotic arm, whilst Crew
Dragon docks via the airlock. That's a significant difference. Also, the
astronauts don't have any control over Crew Dragon, it's completely
autonomous. If something goes wrong, there's nothing they can do to prevent
a catastrophe.


I watched the docking on NASA TV this morning. The crew were definitely
monitoring the approach and even had a display from the Dragon 2 on one
of their laptops. Could they have commanded an abort from that laptop?
I don't know, but it wouldn't surprise me if they could command a hold
or even an abort.


The SpaceX commentary to the docking video makes it quite clear that the
ISS crew can and did command Crew Dragon. At least the following
commands were described as being given from the ISS to Crew Dragon,
during this approach and docking:

- command to turn on the blinking white nav light

- command to retreat from the 150 m waypoint to 180 m

- command to turn on the continuous (non-blinking) white docking light

- command to set the approach speed, when Crew Dragon was again approaching.

In addition, the ISS crew's ability to command abort was clearly stated.

However, when Crew Dragon is docking and very close (one or two meters,
if I remember correctly) there seems to be a "crew hand-off point" at
which ISS crew commanding stops and Crew Dragon is left to dock
autonomously. But it was not clear to me if this is just a procedural
rule, or technically prevented in some way.

--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .
  #5  
Old March 4th 19, 06:14 AM posted to sci.space.policy
Fred J. McCall[_3_]
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Posts: 10,018
Default Dragon2 test flight

Niklas Holsti wrote on Sun, 3 Mar 2019
21:32:59 +0200:


However, when Crew Dragon is docking and very close (one or two meters,
if I remember correctly) there seems to be a "crew hand-off point" at
which ISS crew commanding stops and Crew Dragon is left to dock
autonomously. But it was not clear to me if this is just a procedural
rule, or technically prevented in some way.


It wouldn't surprise me greatly if there is a lockout. We do the same
thing with Man-In-The-Loop missiles based on early experience with
remote operators pulling the missile off target using the manual
controls because the remote display can make it look like the missile
is going to miss when it is right on track to the target. So we
insert a 'MITL Lockout Point' beyond which MITL is disabled. Same
thing with the F/A-18 during carrier launches. It's difficult for
aircrew to not pull back too far on the stick when the cat fires.
There's no mechanized lockout to prevent it, but if you watch a launch
you'll see the pilot reach up and hold a grab handle on the side of
the cockpit. This is so they don't subconsciously pull back on the
controls so that the jet will fly its programmed pattern on launch.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden
  #6  
Old March 4th 19, 08:41 AM posted to sci.space.policy
Fred J. McCall[_3_]
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Posts: 10,018
Default Dragon2 test flight

"Rocket Man" wrote on Sat, 2 Mar 2019
10:17:49 +0100:


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

"JF Mezei" wrote in message
...
Saw an animation of the upcoming Fragon 2 test flight and it included
docking to the station.

Has NASA changed its policy that the first test flight nears the
station
but doesn't get t touch it?

Or have they agreed to let it do the "no touch" test flight and if that
works, then allow it to dock?

Since this is first Dragon flight docking at the modified PMA2 with
totally new guidance/navigation to it, what special steps would be
taken?

Being crewless, will this be totally automated, or will the ISS crew
use
the SpaceX equivalent to the Toru manual remote control ?

I read that the Russians are pretty nervous about Dragon2 since it
doesn't
have an independent backup computer system. If it fails the Dragon2
capsule
may beome uncontrollable and collide with the station. NASA has brushed
aside these concerns, I sure hope they know what they're doing.


From what I understand, Dragon 2 has a triply redundant computer system
so any computer hardware problem shouldn't be an issue. I'd bet the
updated computer hardware on Dragon 2 is at least somewhat based on what
was done with Dragon, which has been successful in terms of its software
used to approach and station keep near ISS so that the SSRMS can grab
it.


The difference is that Cargo Dragon is docked via a robotic arm, whilst Crew
Dragon docks via the airlock. That's a significant difference.


Yeah, I screwed that up a while back and asserted that Dragon 1 did
the auto-docking thing.


Also, the
astronauts don't have any control over Crew Dragon, it's completely
autonomous. If something goes wrong, there's nothing they can do to prevent
a catastrophe.


Which astronauts? The ones on ISS have only limited control (I
think), but I'm sure they can tell it to open away from the station
because they tested that. If it was actually manned rather than a
test the astronauts on board could fly it completely manually.


--
"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
  #8  
Old March 6th 19, 12:34 PM posted to sci.space.policy
Jeff Findley[_6_]
external usenet poster
 
Posts: 2,307
Default Dragon2 test flight

In article ,
says...

On 2019-03-04 02:41, Fred J. McCall wrote:


Yeah, I screwed that up a while back and asserted that Dragon 1 did
the auto-docking thing.


Because your goal was to insult me after I said Dragon 2 used new
untested computers/software for the first time to get to station.
(context was Russians nervous about this single docking computer).


That's because you are simply wrong when you state that "Dragon 2 used
new untested computers/software for the first time to get to station".
That's absolute bull****.

I am absolutely certain that both SpaceX and Boeing's software has been
reviewed, tested, and thoroughly vetted by NASA. No way in hell would
NASA just say "sure, we'll try using your *untested* software to dock
with ISS, we trust you". That's not at all how NASA's current crew
rating standards work!


The bigger point here is that the US has finally proven automated
rendezvous and docking with an actual crew rated vehicle. In reality,
such a feat isn't that hard given modern computers, but it's telling
that this US first was performed by a commercial vehicle, not Orion.

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.
  #9  
Old March 6th 19, 05:06 PM posted to sci.space.policy
Fred J. McCall[_3_]
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Posts: 10,018
Default Dragon2 test flight

JF Mezei wrote on Wed, 6 Mar 2019
03:41:16 -0500:

On 2019-03-04 02:41, Fred J. McCall wrote:

Yeah, I screwed that up a while back and asserted that Dragon 1 did
the auto-docking thing.


Because your goal was to insult me after I said Dragon 2 used new
untested computers/software for the first time to get to station.
(context was Russians nervous about this single docking computer).


And you're a liar. I don't need a reason to insult you. You beg for
it.


--
"Ordinarily he is insane. But he has lucid moments when he is
only stupid."
-- Heinrich Heine
 




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