SpaceX COTS Demo 2/3 Updates (THREAD 2)

[baldusi]

What if the burn is off-nominal?

I'm well aware that lots of analysis is required. And I would ask for lots of testing. But I still don't quite understand if the US will bring the Dragon on a parabolic arc, and then the Dragon will do it's own circularization. Or if the US will bring the Dragon close to the ISS orbit.
This is important because I had assumed the burn after separation from the Dragon would be to bring the US to a different orbital plane. I quite understand that the minimum delta-v maneuver would be to do a 350x750km and then at perigee do a slight plan change. That might be the dangerous part.
But if the US gets the Dragon to the ISS orbit sort of directly, trying to move from it should have very little risk.
I guess the orbital strategy is proprietary, but that's an interesting part of the analysis.
Regarding the statistical analysis, besides the Central Limit Theorem, on symmetric i.i.d stochastic variables, you can approximate a transform of to a t-student past eight samples, and after 30 samples you can get roughly Normal distribution. But too many times non symmetric variables are approximated this way and thus require huge amounts of samples. After all, the CLT doesn't states how many samples are needed. I think engineers are very fond of the Weibull distribution, but for finding the sort of failure that would put the US on a collision course with the ISS can't be easily calculated. I would rather try a backward induction approach. But what do I know about this!

[Ben the Space Brit]

What if the burn is off-nominal?

I'm well aware that lots of analysis is required. And I would ask for lots of testing. But I still don't quite understand if the US will bring the Dragon on a parabolic arc, and then the Dragon will do it's own circularization. Or if the US will bring the Dragon close to the ISS orbit.

My suggestion as an amateur: The initial burn of the U/S places the Dragon-C2/Upper Stage into an orbit with a higher perigee than a normal disposal orbit.  The Dragon seperates, the U/S carries out a plane change manoeuvere at apogee and then the U/S waits until first perigee and then carries out an apogee-raising burn to place the two ORBCOMM vehicles onto their insertion orbit.

[ChefPat]

I sure with there were some UPDATES in the updates thread!!!

[spectre9]

Seems to me like everything got pushed right back because of Progress and the knock on is still being felt.

At least they didn't de-man the ISS 

[Antares]

What if the burn is off-nominal?

And I would ask for lots of testing.

Your instinct is right, but SpaceX long ago made the decision not to ground test on the ground in a vacuum the vacuum engine.  As noted above, that would make the variability of shutdown performance in space based mostly on intuition rather than data.

Edit to fix imprecise language cited by dunderwood below despite having phrased it accurately several times before.

[dunderwood]

The vacuum engine is ground tested, it's just not tested in vacuum.

[FinalFrontier]

It fairly sucks (no other word for it), that the mission date has slipped again. However, if they can pull it off, Imo, slip is more than worth it. It's a pretty challenging thing to go straight from your first flight to an actual docked mission, lets see if they can do it.


I am really looking forward to F9 launches picking up though, as spacex has been pretty focused on cots only for about the last year or so, really looking forward to them starting their main manifest.

[butters]

It must be frustrating for SpaceX. Not too long ago, they thought they were going to be launching as soon as Dec 19, but just a few days ago, they were still receiving new requirements constraining the rendezvous profile. How weird is it that such basic mission parameters are still in flux at this very late stage in the game?

[RocketJack]

It must be frustrating for SpaceX. Not too long ago, they thought they were going to be launching as soon as Dec 19, but just a few days ago, they were still receiving new requirements constraining the rendezvous profile. How weird is it that such basic mission parameters are still in flux at this very late stage in the game?

What new requirements are you talking about?

[Space Pete]

At the NASA Future Forum 2011, Lori Garver just announced that the SpaceX D2/D3 combination is officially approved by NASA, and that the launch date will be 7th Feb.

[Chris Bergin]

At the NASA Future Forum 2011, Lori Garver just announced that the SpaceX D2/D3 combination is officially approved by NASA, and that the launch date will be 7th Feb.

Finally!

[Robotbeat]

At the NASA Future Forum 2011, Lori Garver just announced that the SpaceX D2/D3 combination is officially approved by NASA, and that the launch date will be 7th Feb.

Finally!

Yay! Good that we finally have a more solid launch date, even if we may want it sooner. I agree with those who say we'd rather get it done right instead of rushed.

[Chris Bergin]

Here we go. Totally official now!

Something to look forward too

RELEASE: 11-413

NASA ANNOUNCES LAUNCH DATE AND MILESTONES FOR SPACEX FLIGHT

WASHINGTON -- NASA has announced the launch target for Space
Exploration Technologies' (SpaceX) second Commercial Orbital
Transportation Services (COTS) demonstration flight will be Feb. 7,
2012. Pending completion of final safety reviews, testing and
verification, NASA also has agreed to allow SpaceX to send its Dragon
spacecraft to rendezvous with the International Space Station (ISS)
in a single flight.

"SpaceX has made incredible progress over the last several months
preparing Dragon for its mission to the space station," said William
Gerstenmaier, NASA's associate administrator for the Human
Exploration and Operations Mission Directorate. "We look forward to a
successful mission, which will open up a new era in commercial cargo
delivery for this international orbiting laboratory."

Gerstenmaier said, "There is still a significant amount of critical
work to be completed before launch, but the teams have a sound plan
to complete it and are prepared for unexpected challenges. As with
all launches, we will adjust the launch date as needed to gain
sufficient understanding of test and analysis results to ensure
safety and mission success."

During the flight, Dragon will conduct a series of check-out
procedures that will test and prove its systems in advance of the
rendezvous with the station. The primary objectives for the flight
include a fly-by of the space station at a distance of approximately
two miles to validate the operation of sensors and flight systems
necessary for a safe rendezvous and approach. The spacecraft also
will demonstrate the capability to abort the rendezvous, if required.


Dragon will perform the final approach to the ISS while the station
crew grapples the vehicle with the station's robotic arm. The capsule
will be berthed to the Earth-facing side of the Harmony node. At the
end of the mission, the crew will reverse the process, detaching
Dragon from the station for its return to Earth and splashdown in the
Pacific off the coast of California. If the rendezvous and attachment
to the station are not successful, SpaceX will complete a third
demonstration flight in order to achieve these objectives as
originally planned.

"SpaceX is on the forefront of demonstrating how a partnership between
the government and private industry can lead to new capabilities and
provide a large return on investment," said Alan Lindenmoyer, program
manager for COTS at NASA's Johnson Space Center in Houston.

"SpaceX is excited to be the first commercial company in history to
berth with the International Space Station. This mission will mark a
historic milestone in the future of spaceflight," said SpaceX
President Gwynne Shotwell. "We appreciate NASA's continued support
and their partnership in this process."

Begun in 2006, NASA's COTS program is investing financial and
technical resources to stimulate efforts within the private sector to
develop and demonstrate safe, reliable and cost-effective space
transportation capabilities. In a multiphase strategy, the program is
spurring the innovation and development of new spacecraft and launch
vehicles from commercial industry, creating a new system of
delivering cargo to low-Earth orbit and the International Space
Station.

Through Space Act Agreements, SpaceX will receive up to $396 million
and Orbital Sciences Corporation, NASA's other COTS partner, will
receive up to $288 million for the successful completion of all
milestones in the agreements. To date, SpaceX has received $376
million for completing 36 out of 40 milestones and Orbital has
received $261.5 million for completing 23 out of 29 milestones.

For more information on COTS, visit:

http://www.nasa.gov/cots

For more information on the International Space Station, visit:

http://www.nasa.gov/station

For more information on SpaceX or the Dragon spacecraft, visit:

http://www.spacex.com

[ugordan]

Pending completion of final safety reviews, testing and
verification, NASA also has agreed to allow SpaceX to send its Dragon
spacecraft to rendezvous with the International Space Station (ISS)
in a single flight.

Haven't I heard that already. So, what exactly is different this time round?

T-2 months and holding...

[Chris Bergin]

Good question. I think the key here is NASA announcing the new launch date target. I'd be shocked if they put this out without a large degree of confidence on the final reviews (I guess that's like Shuttle and pre-FRR).

[Jorge]

I think he's referring to the "must do it along the same path taken by the Japanese" thing.

Which was badly garbled, BTW.

[Comga]

Here we go. Totally official now!
Something to look forward to

RELEASE: 11-413
NASA ANNOUNCES LAUNCH DATE AND MILESTONES FOR SPACEX FLIGHT

WASHINGTON -- NASA has announced the launch target for Space Exploration Technologies' (SpaceX) second Commercial Orbital Transportation Services (COTS) demonstration flight will be Feb. 7,
2012. Pending completion of final safety reviews, testing and
verification, NASA also has agreed to allow SpaceX to send its Dragon
spacecraft to rendezvous with the International Space Station (ISS)
in a single flight.

Whoo Hoo!  Here we go!  Finally, some real news.
Now let's see some hardware!

[mr. mark]

Fantastic news! This just made my day.

[jabe]

lets hope the other F9 flights will happen soon there after..
jb

[billh]

Great news! I just love it when the news thread has actual news!