From the updates thread:Quote from: Space Pete on 04/26/2012 10:46 pmSome good views of the Dragon CCP (Crew Command Panel) near the Lab RWS.http://www.spaceflight.nasa.gov/gallery/images/station/crew-30/html/iss030e250643.htmlhttp://www.spaceflight.nasa.gov/gallery/images/station/crew-30/html/iss030e250651.htmlFRGF Sep? Like the crew can command Dragon to ... ? ... do what exactly with its grapple fixture? Is the FRGF held to Dragon with frangible nuts?
Some good views of the Dragon CCP (Crew Command Panel) near the Lab RWS.http://www.spaceflight.nasa.gov/gallery/images/station/crew-30/html/iss030e250643.htmlhttp://www.spaceflight.nasa.gov/gallery/images/station/crew-30/html/iss030e250651.html
Quote from: Jorge on 04/22/2012 05:27 pmQuote from: jabe on 04/22/2012 01:41 pmQuote from: Jorge on 04/22/2012 07:36 amQuote from: sdsds on 04/22/2012 06:37 amWhat'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*zwhere 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.I was thinking of the same question. anda FABULOUS answer... A quick question, I'm assuming x the distance to the station? jbNot in the frame I'm using (NASA LVLH frame). This frame is described as follows:Origin - center of mass of target (ISS)+z - points toward center of Earth (+Rbar)+y - points out-of-plane "starboard", opposite the angular momentum vector (-Hbar)+x - completes a right-handed system, points in the direction of the velocity vector (+Vbar)And of course, dot means velocity and double-dot means acceleration.OK, time for a fun application of these principles to a literary SF example. Moving OT, obviously. I'm flagging this post so the mods can move this subthread appropriately. Not sure where it will end up.Reading assignment: "The Integral Trees" by Larry Niven.Homework questions:1a) Relate the cardinal directions of the Treedwellers to the axes of the NASA LVLH frame described above. Use the diagrams at the front of the book for reference.
Quote from: jabe on 04/22/2012 01:41 pmQuote from: Jorge on 04/22/2012 07:36 amQuote from: sdsds on 04/22/2012 06:37 amWhat'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*zwhere 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.I was thinking of the same question. anda FABULOUS answer... A quick question, I'm assuming x the distance to the station? jbNot in the frame I'm using (NASA LVLH frame). This frame is described as follows:Origin - center of mass of target (ISS)+z - points toward center of Earth (+Rbar)+y - points out-of-plane "starboard", opposite the angular momentum vector (-Hbar)+x - completes a right-handed system, points in the direction of the velocity vector (+Vbar)And of course, dot means velocity and double-dot means acceleration.
Quote from: Jorge on 04/22/2012 07:36 amQuote from: sdsds on 04/22/2012 06:37 amWhat'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*zwhere 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.I was thinking of the same question. anda FABULOUS answer... A quick question, I'm assuming x the distance to the station? jb
Quote from: sdsds on 04/22/2012 06:37 amWhat'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*zwhere 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.
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?
b) What is the origin of the frame, from the perspective of the Treedwellers?
2a) Relate the lines of the Treedwellers' saying:East takes you out.
Out takes you west.
West takes you in.
In takes you east.
Port and starboard bring you back.
to the terms of the C-W equations (attached). 2b) Which term in the C-W equations is not accounted for in the saying?
2c) What force in the Treedwellers' daily experience is represented by the "missing" term?
2d) Why do you think the missing term is not included in the saying?
3) (extra credit) Compare and contrast the dynamics of the integral trees with the severed tether from TSS-1R on STS-75. In particular, what force accounts for the different behavior of the "inward" tuft of the Trees compared to the inward end of the severed tether?
Quote from: Robotbeat on 04/21/2012 03:09 pmQuote from: kch on 04/21/2012 02:58 pmQuote from: Robotbeat on 04/21/2012 02:43 pmQuote from: MP99 on 04/21/2012 02:32 pmI 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, MartinThat'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) Launch2) Deployment of Dragon3) Deployment of solar arrays (and working the radiators)4) Active, precise control of the spacecraft5) 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
Quote from: kch on 04/21/2012 02:58 pmQuote from: Robotbeat on 04/21/2012 02:43 pmQuote from: MP99 on 04/21/2012 02:32 pmI 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, MartinThat'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) Launch2) Deployment of Dragon3) Deployment of solar arrays (and working the radiators)4) Active, precise control of the spacecraft5) Testing all the instruments, communication with ISS, etc.6) Reentry.Really, what is left for COTS-3?
Quote from: Robotbeat on 04/21/2012 02:43 pmQuote from: MP99 on 04/21/2012 02:32 pmI 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, MartinThat's still an option.Launching last year is still an option?
Quote from: MP99 on 04/21/2012 02:32 pmI 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, MartinThat's still an option.
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
The biggest difference between the last flight, which went quite well, and this one is the docking system. So, we have an all new docking system that's never been tested before, and that's gotta go and aquaire the space station, to lock onto the space station, and then plot an approach vector and manoeuvre itself over to dock with the space station, and it's a robotic space craft that's operating under it's own intelligence.
FRGF Sep would be used in the event the SSRMS cannot release Dragon. The HCP, used for HTV and Cygnus, has the same functionality. FRGF Sep must be enabled by the visiting vehicle control center before it is available to the crew, and of course the CCP and HCP implement arm/fire logic along with button covers to preclude inadvertent FRGF Sep.
On the SpaceX update page there's a photo which seems to imply Falcon/Dragon are currently vertical at the pad. (The caption reads, "The SpaceX Dragon spacecraft rests on top of the Falcon 9 rocket at SpaceX’s launch site in Cape Canaveral, FL.") But that's ... wrong?
It's not wrong, it's just an image taken during the last WDR.
It is only the notion that Falcon is vertical at the pad, which could be misconstrued from the image, that would be "wrong."Right?
Probably been pointed out before but in the spirit of patch kremlinology...There are three stars 'in the drink' (representing the three failed Falcon 1's?) and three in space (the successful F1 plus the two falcon 9's?)
For at least the third time on this site. )
Quote from: Robotbeat on 04/29/2012 11:01 pmFor at least the third time on this site. )Indeed.It's just a patch people, stop trying to "read the tea leaves". The stars don't mean anything. If y'all want a mystery to solve, ask why the arm is coming from the wrong side.
Quote from: Robotbeat on 04/29/2012 11:01 pmFor at least the third time on this site. )Indeed.It's just a patch people, stop trying to "read the tea leaves".
