SpaceX Falcon 9/Dragon COTS Demo (C2+) GENERAL DISCUSSION

[SpacexULA]

with ATV and HTV being successful first try... those missions had same complexity?  Or did they do THAT much more testing before flight to reduce risk of failure?
jb

One big difference between ATV/HTV and SpaceX is the experience of the companies involved.

ATV is a program funded by ESA, but with EADS Astrium as the primary contractor.  I say primary contractor because EADS Astrium does not do all the work in house, they contracted out large chunks of the vehicle to contractors that already had experience with Satellites and ISS Modules.

HTV is a program of JAXA, but with Mitsubishi Heavy Industry as the primary contractor.  Again MHI did a bulk of the assembly, but many aspects of the vehicle where contacted out to the same contractors who worked on the Kibo module on the ISS.

SpaceX is a bit different because the vast majority of its components where manufactured in house by a company without a long track record of producing the systems that are going to be critical to the mission success.

An example of this is the solar arrays of HTV & ATV where manufactured by companies that had LONG track records of successful solar array projects on communication satellites.  SpaceX's solar array was manufactured in house, and these solar arrays are the 1st ever produces by SpaceX (not to say the 1st solar arrays manufactured by the team within SpaceX, they have many managers from other established companies)..

I think that's part of the reason that people are not quite as worried about Orbital's Cygnus as they are about the Dragon, Orbital is already a world class Satellite manufacture, and outsourced everything that they didn't have a lot of experience with

[Robotbeat]

I just read that Musk told National Geographic that he gave the upcoming COTS mission only a 60% chance of total success. That is just slightly better than a coin toss! He sure is becoming less of an optomist in his old age...

"Musk knows that many setbacks await. He places the odds at total success for Dragon's upcoming mission, including successful docking with the ISS, at perhaps 60 percent."

http://news.nationalgeographic.com/news/2012/04/120416-nasa-spacex-dragon-launch-readiness-space-station-science/

I can't help wondering if SpaceX could have launched a pure COTS2 mission sometime last year, and how much that would have reduced the risk of the following COTS3 mission.

cheers, Martin

That's still an option.

[kch]

I can't help wondering if SpaceX could have launched a pure COTS2 mission sometime last year, and how much that would have reduced the risk of the following COTS3 mission.

cheers, Martin

That's still an option.

Launching last year is still an option? 

[Robotbeat]

I can't help wondering if SpaceX could have launched a pure COTS2 mission sometime last year, and how much that would have reduced the risk of the following COTS3 mission.

cheers, Martin

That's still an option.

Launching last year is still an option? 

All of the major risks will happen on the COTS 2 portion, anyway. They have to demonstrate:
1) Launch
2) Deployment of Dragon
3) Deployment of solar arrays (and working the radiators)
4) Active, precise control of the spacecraft
5) Testing all the instruments, communication with ISS, etc.
6) Reentry.

Really, what is left for COTS-3? Hardly anything. Once they do the COTS-2 objectives during this coming flight, all the biggest risks of mission failure are over with (except reentry). To berth, they just have to maintain control near the station, and the ISS crew handles the rest. All the infant fatalities are already behind them at that point, and they've already had to demonstrate that everything worked.

The big risk is the COTS-2 objectives, NOT the COTS-3 objectives. IMHO.

Even if they fail in the objectives, there's a good chance they can reenter successfully, so they can recover all the stuff on this flight (and perhaps launch this Dragon for some other mission). Then, they can launch COTS-3 the next flight.

[MP99]

I just read that Musk told National Geographic that he gave the upcoming COTS mission only a 60% chance of total success. That is just slightly better than a coin toss! He sure is becoming less of an optomist in his old age...

"Musk knows that many setbacks await. He places the odds at total success for Dragon's upcoming mission, including successful docking with the ISS, at perhaps 60 percent."

http://news.nationalgeographic.com/news/2012/04/120416-nasa-spacex-dragon-launch-readiness-space-station-science/

I can't help wondering if SpaceX could have launched a pure COTS2 mission sometime last year, and how much that would have reduced the risk of the following COTS3 mission.

That's still an option.

There's not even a guarantee this flight will pass the COTS2 tests, but that's not the point.

If SpaceX had concentrated on COTS2, how early could that have flown, and would it have delayed this COTS3 flight?

cheers, Martin

[MP99]

I can't help wondering if SpaceX could have launched a pure COTS2 mission sometime last year, and how much that would have reduced the risk of the following COTS3 mission.

cheers, Martin

That's still an option.

Launching last year is still an option? 

All of the major risks will happen on the COTS 2 portion, anyway. They have to demonstrate:
1) Launch
2) Deployment of Dragon
3) Deployment of solar arrays (and working the radiators)
4) Active, precise control of the spacecraft
5) Testing all the instruments, communication with ISS, etc.
6) Reentry.

Really, what is left for COTS-3?

How much extra work did they have to do with NASA to convince them it would be safe to approach and dock if COTS2 milestones were signed off?

How much software is unique to the actual berthing process and berthed operations?

HR of Dragon for ISS crew to enter.

Docked thermal environment.

Impact of Dragon to ISS's environment.

Anything to do with cargo / stowage / late access to Dragon during launch ops.

cheers, Martin

[jabe]

SpaceX is a bit different because the vast majority of its components where manufactured in house by a company without a long track record of producing the systems that are going to be critical to the mission success.

Good points.. Going to be an interesting launch.  Hope F9 as planned works so they can test the systems..
jb

[Prober]

I just read that Musk told National Geographic that he gave the upcoming COTS mission only a 60% chance of total success. That is just slightly better than a coin toss! He sure is becoming less of an optomist in his old age...

"Musk knows that many setbacks await. He places the odds at total success for Dragon's upcoming mission, including successful docking with the ISS, at perhaps 60 percent."

http://news.nationalgeographic.com/news/2012/04/120416-nasa-spacex-dragon-launch-readiness-space-station-science/

I can't help wondering if SpaceX could have launched a pure COTS2 mission sometime last year, and how much that would have reduced the risk of the following COTS3 mission.

That's still an option.

There's not even a guarantee this flight will pass the COTS2 tests, but that's not the point.

If SpaceX had concentrated on COTS2, how early could that have flown, and would it have delayed this COTS3 flight?

cheers, Martin

It's looking like SpaceX might (key word) wasn't ready for the Cots2 flight last year.   

After watching that NASA briefing of the COTS2 milestones;  one screwup, and they have little fuel margin to complete the milestones.

What'  Astonishing is SpaceX management pushing to launch those sat payloads prior to Cots2 milestones being completed.   SpaceX management lost site of who their customer was, NASA.

Not posted to start an argument, it’s a review of the history of last year.
 

[SpacexULA]

It's looking like SpaceX might (key word) wasn't ready for the Cots2 flight last year.   

After watching that NASA briefing of the COTS2 milestones;  one screwup, and they have little fuel margin to complete the milestones.

What'  Astonishing is SpaceX management pushing to launch those sat payloads prior to Cots2 milestones being completed.   SpaceX management lost site of who their customer was, NASA.

Not posted to start an argument, it’s a review of the history of last year.

Payloads where to be deployed before going to ISS, so minimal if any extra fuel from Dragon, from what I remember payloads where to be deployed after separation but before acceleration to catch up to ISS.

If you paid attention, different sections of this demo require different amounts of fuel, and NASA is open to the idea of allowing SpaceX to repeat any section until they don't have enough fuel. 

Considering how fuel intensive the COTS3 milestones are it's amazing they have enough fuel to even consider reattempting.

[Robotbeat]

It's looking like SpaceX might (key word) wasn't ready for the Cots2 flight last year.   

After watching that NASA briefing of the COTS2 milestones;  one screwup, and they have little fuel margin to complete the milestones.

What'  Astonishing is SpaceX management pushing to launch those sat payloads prior to Cots2 milestones being completed.   SpaceX management lost site of who their customer was, NASA.

Not posted to start an argument, it’s a review of the history of last year.

Payloads where to be deployed before going to ISS, so minimal if any extra fuel from Dragon, from what I remember payloads where to be deployed after separation but before acceleration to catch up to ISS.

If you paid attention, different sections of this demo require different amounts of fuel, and NASA is open to the idea of allowing SpaceX to repeat any section until they don't have enough fuel. 

Considering how fuel intensive the COTS3 milestones are it's amazing they have enough fuel to even consider reattempting.

Wait, what evidence do you have that it requires "lots of fuel"? The only figures I remember say something like ~1xx m/s of delta-v for the milestones, whereas they should have a few times that amount of propellant on board (since they are packed so light), thus they may well have potential capability for several re-dos.

[SpacexULA]

Payloads where to be deployed before going to ISS, so minimal if any extra fuel from Dragon, from what I remember payloads where to be deployed after separation but before acceleration to catch up to ISS.

If you paid attention, different sections of this demo require different amounts of fuel, and NASA is open to the idea of allowing SpaceX to repeat any section until they don't have enough fuel. 

Considering how fuel intensive the COTS3 milestones are it's amazing they have enough fuel to even consider reattempting.

Wait, what evidence do you have that it requires "lots of fuel"? The only figures I remember say something like ~1xx m/s of delta-v for the milestones, whereas they should have a few times that amount of propellant on board (since they are packed so light), thus they may well have potential capability for several re-dos.[/quote]

Maybe I read to much into it but in the press conferance the Flight Director said the back and forth aproaches to the ISS was a fuel intensive section of the flight.  I have no where near the knowlege you do, so I will asume your right.

[A_M_Swallow]

Strawberries are in season all over the Southern US right now. Especially Florida.
(hint, hint)

Strawberry pie a nice surprice.

Someone needs to invent a strawberry pie or cake that does not crumble.

[Robotbeat]

...I have no where near the knowlege you do, so I will asume your right.

Well, there's where you're wrong.

I just seem to remember that Dragon carries a lot of propellant and that the milestones didn't have THAT much delta-v requirements. Still, I'd much prefer direct documentation over my faulty memory.

[Prober]

Payloads where to be deployed before going to ISS, so minimal if any extra fuel from Dragon, from what I remember payloads where to be deployed after separation but before acceleration to catch up to ISS.

If you paid attention, different sections of this demo require different amounts of fuel, and NASA is open to the idea of allowing SpaceX to repeat any section until they don't have enough fuel. 

Considering how fuel intensive the COTS3 milestones are it's amazing they have enough fuel to even consider reattempting.

Wait, what evidence do you have that it requires "lots of fuel"? The only figures I remember say something like ~1xx m/s of delta-v for the milestones, whereas they should have a few times that amount of propellant on board (since they are packed so light), thus they may well have potential capability for several re-dos.

Maybe I read to much into it but in the press conferance the Flight Director said the back and forth aproaches to the ISS was a fuel intensive section of the flight.  I have no where near the knowlege you do, so I will asume your right.
[/quote]
 
Yes, maybe I read too much into it, but when the FD was talking about the various charts and stopping points etc. she did note issues about fuel use.

[daveklingler]

Hi guys.  I posted a "Good luck to SpaceX" petition over at an online petition website, just for kicks.  It would be cool if it picked up a bunch of signatures in the next couple of weeks, so tweet!

http://www.change.org/petitions/spacex-we-wish-spacex-success-in-their-attempt-to-dock-with-the-space-station

[spacetraveler]

Maybe I read to much into it but in the press conferance the Flight Director said the back and forth aproaches to the ISS was a fuel intensive section of the flight.  I have no where near the knowlege you do, so I will asume your right.

She did say it was fuel intensive, but I don't recall any specifics on what percentage of Dragon's fuel capacity it represented or how many attempts could likely be done.

[SpacexULA]

She did say it was fuel intensive, but I don't recall any specifics on what percentage of Dragon's fuel capacity it represented or how many attempts could likely be done.

That is what I was going off of.  I never saw the flight director say any part of the mission could not be repeated... I hope this all goes very smoothly.

[Robotbeat]

She did say it was fuel intensive, but I don't recall any specifics on what percentage of Dragon's fuel capacity it represented or how many attempts could likely be done.

That is what I was going off of.  I never saw the flight director say any part of the mission could not be repeated... I hope this all goes very smoothly.

I seem to remember the implication is that Dragon would be able to redo the whole process if there's an abort.

Does anyone know the nominal mission total delta-v?

[sdsds]

What's the best approach to calculating the delta-v per second consumed by Dragon as it holds position a fixed distance below the station on the r-bar?

[Jorge]

What's the best approach to calculating the delta-v per second consumed by Dragon as it holds position a fixed distance below the station on the r-bar?

Clohessy-Wiltshire equations. If using the NASA LVLH frame (Rbar = z axis), take the z equation, set x-dot to zero, and solve for z-double-dot as a function of z:

z-double-dot = 3*n^2*z

where n is the mean motion (orbital rate), about 0.0011 rad/sec for ISS orbit.

Note that for most spacecraft, including Dragon, the same delta-v in different axes may result in different propellant consumption due to the different canting of RCS thrusters.