Author Topic: General Falcon and Dragon discussion (Thread 11)  (Read 248069 times)

Offline mme

  • Full Member
  • ****
  • Posts: 833
  • Santa Barbara, CA, USA, Earth, Solar System, Milky Way Galaxy, Virgo Supercluster
  • Liked: 967
  • Likes Given: 2167
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #700 on: 02/06/2015 02:06 AM »
Will SpaceX try the fast-track route to the ISS as the Russians?
I can't find the reference, but I recall Hans Koenigsmann responding to a question at a NASA presser that SpaceX would use the 6 hour flight plan with crew.
Mark

Offline cscott

  • Senior Member
  • *****
  • Posts: 2273
  • Liked: 1568
  • Likes Given: 653
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #701 on: 02/06/2015 07:44 AM »
Will SpaceX try the fast-track route to the ISS as the Russians?
I can't find the reference, but I recall Hans Koenigsmann responding to a question at a NASA presser that SpaceX would use the 6 hour flight plan with crew.

Yeah, I remember that, too.  He claimed that Dragon 1 was already technically capable of doing fast rendezvous, but fast rendezvous requires thruster burns on the ISS side as well and NASA saw no need to waste ISS propellant when it's only cargo going up.

Offline Comga

  • Senior Member
  • *****
  • Posts: 3668
  • Liked: 1104
  • Likes Given: 925
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #702 on: 02/07/2015 08:24 PM »
SpaceflightNow has posted a timeline for the DSCOVR launch.  Among the images, the one for the jettison of the fairing is particularly interesting.  It appears to be from the first stage. 
Is this a photo from the first stage, from a ground asset, or a simulation?
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 30175
  • Cape Canaveral Spaceport
  • Liked: 8483
  • Likes Given: 271
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #703 on: 02/07/2015 08:43 PM »
sim

Offline dror

  • Full Member
  • ****
  • Posts: 456
  • Israel
  • Liked: 94
  • Likes Given: 247
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #704 on: 02/12/2015 06:06 PM »
SpaceflightNow has posted a timeline for the DSCOVR launch.  Among the images, the one for the jettison of the fairing is particularly interesting.  It appears to be from the first stage. 
Is this a photo from the first stage, from a ground asset, or a simulation?
Now thats the picture from the ground:
http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36765.0;attach=711336;image

Offline Coastal Ron

  • Senior Member
  • *****
  • Posts: 2811
  • I live... along the coast
  • Liked: 1735
  • Likes Given: 1873
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #705 on: 02/12/2015 08:08 PM »
Will SpaceX try the fast-track route to the ISS as the Russians?
I can't find the reference, but I recall Hans Koenigsmann responding to a question at a NASA presser that SpaceX would use the 6 hour flight plan with crew.

Yeah, I remember that, too.  He claimed that Dragon 1 was already technically capable of doing fast rendezvous, but fast rendezvous requires thruster burns on the ISS side as well and NASA saw no need to waste ISS propellant when it's only cargo going up.

Wow, you wouldn't think that the relatively puny thrusters on the 450mT ISS could make that much of a difference for a rendezvous in such a short period of time.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline Zardar

  • Full Member
  • *
  • Posts: 119
  • Limerick, Ireland
  • Liked: 57
  • Likes Given: 140
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #706 on: 02/12/2015 08:27 PM »
Will SpaceX try the fast-track route to the ISS as the Russians?
I can't find the reference, but I recall Hans Koenigsmann responding to a question at a NASA presser that SpaceX would use the 6 hour flight plan with crew.

Yeah, I remember that, too.  He claimed that Dragon 1 was already technically capable of doing fast rendezvous, but fast rendezvous requires thruster burns on the ISS side as well and NASA saw no need to waste ISS propellant when it's only cargo going up.

Wow, you wouldn't think that the relatively puny thrusters on the 450mT ISS could make that much of a difference for a rendezvous in such a short period of time.

They Dont!
There's a launch opportunity ~once a day to reach the ISS on a slow rendezvous - the ISS just has to be in the same plane as the launch site at the instant of launch, but you don't care much WHERE it is on the plane (even on the other side of the earth) since the dragon can drift 'along' that plane over a few days by being in a slightly higher or lower orbit.

But, if you want a fast rendezvous, the ISS has to be in the same plane, and effectively at the same position as the dragon once it reaches orbit. (visualise the ISS as in plane, and also nearly over, the launch pad at the moment of launch) This occurs very rarely under normal operations. So, it has to be set up days in advance, by first raising and lowering the ISS's orbit, and letting the ISS do the drifting, towards or away, along the plane, from where the dragon is expected to be when it reaches orbit. That takes a fair bit of fuel and planning, and if the falcon scrubs, its all for naught. And then you have to lower/raise the whole station again!
They do it for soyuz spacecraft  launches, since they have human cargo, cramped in a tiny can, and the soyuz has a damn good on-time launch record!


Offline Coastal Ron

  • Senior Member
  • *****
  • Posts: 2811
  • I live... along the coast
  • Liked: 1735
  • Likes Given: 1873
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #707 on: 02/12/2015 09:07 PM »
Wow, you wouldn't think that the relatively puny thrusters on the 450mT ISS could make that much of a difference for a rendezvous in such a short period of time.

They Dont!
There's a launch opportunity ~once a day to reach the ISS on a slow rendezvous - the ISS just has to be in the same plane as the launch site at the instant of launch, but you don't care much WHERE it is on the plane (even on the other side of the earth) since the dragon can drift 'along' that plane over a few days by being in a slightly higher or lower orbit.

But, if you want a fast rendezvous, the ISS has to be in the same plane, and effectively at the same position as the dragon once it reaches orbit. (visualise the ISS as in plane, and also nearly over, the launch pad at the moment of launch) This occurs very rarely under normal operations. So, it has to be set up days in advance, by first raising and lowering the ISS's orbit, and letting the ISS do the drifting, towards or away, along the plane, from where the dragon is expected to be when it reaches orbit. That takes a fair bit of fuel and planning, and if the falcon scrubs, its all for naught. And then you have to lower/raise the whole station again!
They do it for soyuz spacecraft  launches, since they have human cargo, cramped in a tiny can, and the soyuz has a damn good on-time launch record!

Great explanation.  Apparently the Soyuz and it's carrier rocket don't have enough extra maneuvering capability, so the ISS has to "help".  I wonder if the Dragon and CST-100 will have enough maneuvering capability to reach the ISS without the ISS needing to help?
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline Zardar

  • Full Member
  • *
  • Posts: 119
  • Limerick, Ireland
  • Liked: 57
  • Likes Given: 140
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #708 on: 02/12/2015 11:07 PM »

Great explanation.  Apparently the Soyuz and it's carrier rocket don't have enough extra maneuvering capability, so the ISS has to "help".  I wonder if the Dragon and CST-100 will have enough maneuvering capability to reach the ISS without the ISS needing to help?

They would have plenty of fuel/ delta-v to rendezvous, but only if you wish to spend  several days phasing on orbit!
If the two craft are in plane, and at approx the same ISS altitude , but completely out of phase (i.e. on opposite sides of the earth), then effectively they are 45 mins apart.
To catch up (or fall back), over the course of 2 days, at one orbit every ~90 mins (or 16 orbits a day), thats only 1.5 mins per orbit.
But, if you try to do it fast, in less time/orbits, you will need such a high or low intermediate orbit that the fuel burned to go up and back down again would be excessive, or else you're so low you'd re-enter.
And, more importantly, you would sort-of end up 'alongside' the ISS at the end of your maneuvers, but in a different plane, orbiting parallel to it, but way off to the side, and a plane change is very expensive in delta-v. (you can't just thrust 'across', like jumping from one train to another on parallel tracks, since that would effectively be an inclination change)


Offline Coastal Ron

  • Senior Member
  • *****
  • Posts: 2811
  • I live... along the coast
  • Liked: 1735
  • Likes Given: 1873
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #709 on: 02/12/2015 11:16 PM »

Great explanation.  Apparently the Soyuz and it's carrier rocket don't have enough extra maneuvering capability, so the ISS has to "help".  I wonder if the Dragon and CST-100 will have enough maneuvering capability to reach the ISS without the ISS needing to help?

They would have plenty of fuel/ delta-v to rendezvous, but only if you wish to spend  several days phasing on orbit!
If the two craft are in plane, and at approx the same ISS altitude , but completely out of phase (i.e. on opposite sides of the earth), then effectively they are 45 mins apart.
To catch up (or fall back), over the course of 2 days, at one orbit every ~90 mins (or 16 orbits a day), thats only 1.5 mins per orbit.
But, if you try to do it fast, in less time/orbits, you will need such a high or low intermediate orbit that the fuel burned to go up and back down again would be excessive, or else you're so low you'd re-enter.
And, more importantly, you would sort-of end up 'alongside' the ISS at the end of your maneuvers, but in a different plane, orbiting parallel to it, but way off to the side, and a plane change is very expensive in delta-v. (you can't just thrust 'across', like jumping from one train to another on parallel tracks, since that would effectively be an inclination change)

I'm getting better educated on this.  So are you saying that even if the Falcon 9 2nd stage was loaded up with more propellant and was able to do more maneuvering burns in orbit with the Dragon still attached (assuming that didn't rip the solar panels off of the Dragon), that it still wouldn't be enough to do a fast rendezvous with no ISS engine burns?

No doubt there is some amount of energy an approaching vehicle can use to do the fast approach on their own, but the question is whether either of the Commercial Crew vehicles and their carrier rockets would have that much energy available to use?
« Last Edit: 02/12/2015 11:18 PM by Coastal Ron »
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline Space OurSoul

  • Full Member
  • **
  • Posts: 220
  • Seattle, WA
  • Liked: 126
  • Likes Given: 28
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #710 on: 02/12/2015 11:34 PM »
Hey gang,
Anybody know how F9 second stage does ullage?
A friend asked and I realized I didn't know...

thanks
A complete OurSoul

Offline Lars-J

  • Senior Member
  • *****
  • Posts: 2579
  • California
  • Liked: 2029
  • Likes Given: 1137
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #711 on: 02/13/2015 12:01 AM »
Hey gang,
Anybody know how F9 second stage does ullage?
A friend asked and I realized I didn't know...

thanks

I believe it uses Nitrogen RCS, just like the first stage does. But with much smaller thrusters. But I don't know for sure.

I think you can see one firing in the bottom left corner of this picture: (unless that is just venting)

Offline Ben the Space Brit

  • Senior Member
  • *****
  • Posts: 6755
  • A spaceflight fan
  • London, UK
  • Liked: 426
  • Likes Given: 468
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #712 on: 02/17/2015 08:54 AM »
Hey gang,
Anybody know how F9 second stage does ullage?
A friend asked and I realized I didn't know...

thanks

I'd thought that the U/S had a Draco RCS thruster array based on the one on Dragon for both attitude control and repositioning. However, it doesn't look like it. As SpaceX are getting good performance of the smaller, simpler and lighter GN2 thrusters used on the core, I don't see any reason why the same sort of system shouldn't be on the upper stage.
"Oops! I left the silly thing in reverse!" - Duck Dodgers

~*~*~*~

The Space Shuttle Program - 1981-2011

The time for words has passed; The time has come to put up or shut up!
DON'T PROPAGANDISE, FLY!!!

Offline douglas100

  • Senior Member
  • *****
  • Posts: 2110
  • Liked: 188
  • Likes Given: 86
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #713 on: 02/17/2015 09:38 AM »

[...I'm getting better educated on this.  So are you saying that even if the Falcon 9 2nd stage was loaded up with more propellant and was able to do more maneuvering burns in orbit with the Dragon still attached (assuming that didn't rip the solar panels off of the Dragon), that it still wouldn't be enough to do a fast rendezvous with no ISS engine burns?

Correct. As Zardar explained, the orbital phasing must be set up in advance by the ISS. It's not just a matter of  "giving Soyuz a helping hand." All visiting vehicles are in the same situation.

Quote
...No doubt there is some amount of energy an approaching vehicle can use to do the fast approach on their own, but the question is whether either of the Commercial Crew vehicles and their carrier rockets would have that much energy available to use?

If the ISS is 180 degrees out of phase only some kind of magic propellantless propulsion is going to allow you to reach it in a few hours. Anyway, it's unnecessary. Setting up the phasing in advance allows any visiting vehicle to do a fast approach, in principle.
Douglas Clark

Offline Chris Bergin

Re: General Falcon and Dragon discussion (Thread 11)
« Reply #714 on: 02/17/2015 10:33 AM »
I think this is a good point to start a thread 12 then. Keep everyone focused (long threads always tend to wander).

Link:
http://forum.nasaspaceflight.com/index.php?topic=36815.0

Leaving this one unlocked for the interim to allow quoting and continued discussion on the new thread, but please  post in the new thread!

Offline fatjohn1408

  • Full Member
  • ***
  • Posts: 313
  • Liked: 13
  • Likes Given: 13
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #715 on: 03/05/2015 08:31 AM »
http://www.wsj.com/articles/BL-DGB-40041

Quote
SpaceXís Valuation Rockets to $12 Billion With Google Investment

SpaceX now ranks fourth on The Wall Street Journalís list of billion-dollar private companies, securing a $12 billion valuation.
>

I'm not sure I would have taken up that deal if I were google.
12 billion is a hell of a lot. If they launch 10 times and launch a couple of dragons as well, they have a yearly revenue of a billion. This is already stretching their revenue expectations for this year. So their valuation is 12 times their revenue? How many companies outside of websites have such a valuation?
Airbus group (note they make a couple of planes, fighterjets, helicopters and missiles as well) has a valuation of only 50B.

SpaceX just got handed a shitload of money. Which of course is great, rather see Google wasting it on SpaceX than giving it to people that try to make an algorithm to present me the best personalized add on my screen.

Offline docmordrid

  • Senior Member
  • *****
  • Posts: 3986
  • Michigan
  • Liked: 1247
  • Likes Given: 1
Re: General Falcon and Dragon discussion (Thread 11)
« Reply #716 on: 03/05/2015 09:08 AM »
There's a couple of subtexts

1) Google wants, more like needs, to expand its usership worldwide and wants  that satellite constellation to do it. This would be a parallel path to its fiber network. Getting in bed with a cheap launch company eases that.

As for SpaceX, this is just what they need to keep Vandenberg and Texas busy, launching a couple dozen netsats per flight, then replacing 15-20% of the constellation every year or so.

2) Larry Page and Elon Musk are old pals, and Page has said he'd rather leave his billions to Musk for SpaceX etc. than other options .
« Last Edit: 03/05/2015 09:10 AM by docmordrid »
DM

Tags: