Quote from: Stan-1967 on 02/23/2017 04:11 amQuote from: Kaputnik on 02/23/2017 01:18 amHow far downrange will they be when they hit the atmosphere?And does anyone know the airspeed velocity of an unladen payload fairing?Considering the fairings are made by RUAG Space, we need to use the data tables for unladen European payload fairings. SpaceX makes their own fairings, but a goog joke nonetheless. (RUAG makes the Atlas V and Ariane V fairings)
Quote from: Kaputnik on 02/23/2017 01:18 amHow far downrange will they be when they hit the atmosphere?And does anyone know the airspeed velocity of an unladen payload fairing?Considering the fairings are made by RUAG Space, we need to use the data tables for unladen European payload fairings.
How far downrange will they be when they hit the atmosphere?And does anyone know the airspeed velocity of an unladen payload fairing?
Quote from: cscott on 02/23/2017 12:55 pmI think woods170 may be referring to loads during horizontal integration.Correct. See Jim's explanation of it here: https://forum.nasaspaceflight.com/index.php?topic=39181.msg1561918#msg1561918And Joek's drawing of it here: https://forum.nasaspaceflight.com/index.php?topic=39181.msg1561934#msg1561934And Jim's endorsement of Joek's drawing here: https://forum.nasaspaceflight.com/index.php?topic=39181.msg1561969#msg1561969And this news article shows a rare image of an encapsulated payload going horizontal: https://www.noozhawk.com/noozhawk/print/falcon_9_rocket_moving_toward_nasa_launch_at_vandenberg_afbYou will notice that the payload and fairing are not held via the PAF (Payload Attachment Fitting), but via the fairing halves. Consequently, the load of the payload goes thru the fairing, not the PAF. This requires a strong fairing. Much stronger than those from RUAG et al.
I think woods170 may be referring to loads during horizontal integration.
Quote from: woods170 on 02/23/2017 01:06 pm[...]And this news article shows a rare image of an encapsulated payload going horizontal: https://www.noozhawk.com/noozhawk/print/falcon_9_rocket_moving_toward_nasa_launch_at_vandenberg_afbYou will notice that the payload and fairing are not held via the PAF (Payload Attachment Fitting), but via the fairing halves. Consequently, the load of the payload goes thru the fairing, not the PAF. This requires a strong fairing. Much stronger than those from RUAG et al.The fairing doesn't carry the payload since it doesn't touch it. At worst, during horizontal integration, the fairing half carries its own weight.There was never a good explanation of why they are heavy, except perhaps the desire for them to survive reentry.
[...]And this news article shows a rare image of an encapsulated payload going horizontal: https://www.noozhawk.com/noozhawk/print/falcon_9_rocket_moving_toward_nasa_launch_at_vandenberg_afbYou will notice that the payload and fairing are not held via the PAF (Payload Attachment Fitting), but via the fairing halves. Consequently, the load of the payload goes thru the fairing, not the PAF. This requires a strong fairing. Much stronger than those from RUAG et al.
Quote from: woods170 on 02/23/2017 01:06 pmQuote from: cscott on 02/23/2017 12:55 pmI think woods170 may be referring to loads during horizontal integration.Correct. See Jim's explanation of it here: https://forum.nasaspaceflight.com/index.php?topic=39181.msg1561918#msg1561918And Joek's drawing of it here: https://forum.nasaspaceflight.com/index.php?topic=39181.msg1561934#msg1561934And Jim's endorsement of Joek's drawing here: https://forum.nasaspaceflight.com/index.php?topic=39181.msg1561969#msg1561969And this news article shows a rare image of an encapsulated payload going horizontal: https://www.noozhawk.com/noozhawk/print/falcon_9_rocket_moving_toward_nasa_launch_at_vandenberg_afbYou will notice that the payload and fairing are not held via the PAF (Payload Attachment Fitting), but via the fairing halves. Consequently, the load of the payload goes thru the fairing, not the PAF. This requires a strong fairing. Much stronger than those from RUAG et al.The fairing doesn't carry the payload since it doesn't touch it. At worst, during horizontal integration, the fairing half carries its own weight.There was never a good explanation of why they are heavy, except perhaps the desire for them to survive reentry.
But to be perfectly clear... When the fairing is supported the load of the payload goes through the PAF and then to the fairing. There is no direct connection between the payload and fairing.Correct?
There was never a good explanation of why they are heavy, except perhaps the desire for them to survive reentry.
Quote from: meekGee on 02/23/2017 02:28 pmThere was never a good explanation of why they are heavy, except perhaps the desire for them to survive reentry.Surviving the transition to supersonic and max-q are the reasons. The thing is really large (it would easily swallow most people's entire living room), and max-q is a lot of force distributed over a lot of area.
In that case, the loading seems to me very similar to what a fairing normally experiences, or even more benign.
Quote from: meekGee on 02/23/2017 06:14 pmIn that case, the loading seems to me very similar to what a fairing normally experiences, or even more benign.It is nowhere near the same. On most other vehicles, the fairing never sees any loads from the payload. They could not be used in the same
FWIW, if maxQ is about 30 kPa, and the fairing were to present an area of 15 m2 to the wind, that's 45 tons of force.
Quote from: meekGee on 02/23/2017 06:14 pmFWIW, if maxQ is about 30 kPa, and the fairing were to present an area of 15 m2 to the wind, that's 45 tons of force.That is an axial load and not the same as a side load
Quote from: Jim on 02/23/2017 06:18 pmQuote from: meekGee on 02/23/2017 06:14 pmIn that case, the loading seems to me very similar to what a fairing normally experiences, or even more benign.It is nowhere near the same. On most other vehicles, the fairing never sees any loads from the payload. They could not be used in the sameJust a matter of distributing the loads. SpaceX clearly designed for this, but it shouldn't double the mass of the fairing. Worst case they'd have added a ribbed structure from the support point to the payload ring, which would not weight multiple tons. (And I don't think they needed to do that either).What makes the SpaceX fairing twice as heavy as other fairings has to be a fairing-wide issue, and the only thing that fits the bill is either incompetence (they don't know how to build a lightweight fairing) or some unique aerodynamic requirements - and the second option is staring us right in the face, since we know they're trying recovery.
Quote from: meekGee on 02/23/2017 06:28 pmQuote from: Jim on 02/23/2017 06:18 pmQuote from: meekGee on 02/23/2017 06:14 pmIn that case, the loading seems to me very similar to what a fairing normally experiences, or even more benign.It is nowhere near the same. On most other vehicles, the fairing never sees any loads from the payload. They could not be used in the sameJust a matter of distributing the loads. SpaceX clearly designed for this, but it shouldn't double the mass of the fairing. Worst case they'd have added a ribbed structure from the support point to the payload ring, which would not weight multiple tons. (And I don't think they needed to do that either).What makes the SpaceX fairing twice as heavy as other fairings has to be a fairing-wide issue, and the only thing that fits the bill is either incompetence (they don't know how to build a lightweight fairing) or some unique aerodynamic requirements - and the second option is staring us right in the face, since we know they're trying recovery.Or a structural requirement. The pictures clearly show the fairing with enclosed payload being lifted by the middle of the fairing. From other's comments here, such an operation never happens with fairings for other rockets. SpaceX probably does this for some reason based on their processing flow (maybe not having to have special equipment to deal with the torque on the payload adapter before the adapter gets attached to the rocket.)Aerodynamic concerns for recovery don't make sense, because information relating to fairing recovery has indicated that the current fairings were not designed for recovery. The current fairings were designed long before they would have been ready to seriously consider fairing recovery.Also, you are really, really oversimplifying structural analysis in some of your posts.
As for when did SpaceX start thinking about fairing recovery - I don't know, and neither do you. It's clearly not the final design, but whether they were built more robustly to enable even initial experimentation - we simply can't tell. But probably earlier than a year ago...
Quote from: meekGee on 02/23/2017 06:50 pmAs for when did SpaceX start thinking about fairing recovery - I don't know, and neither do you. It's clearly not the final design, but whether they were built more robustly to enable even initial experimentation - we simply can't tell. But probably earlier than a year ago...The fairing design predates the first launch
....Also shines new light on the payload restrictions of about 10 T to the current payload. It was speculated that FH can not bring heavy payloads to LEO because the adapter is not capable to hold heavy loads. Maybe the adapter is not the limitation.. Maybe it's the fairing.