On 2024-05-25 5:06 a.m., Niklas Holsti wrote:
For IFT-4, they say that there are "operational changes including the
jettison of the Super HeavyrCOs hot-stage adapter following boostback to
reduce booster mass for the final phase of flight." What, so that part
will fall into the ocean and not be reused? This is a surprising
departure from earlier principles. Perhaps it is only a temporary
work-around.
Indeed, it is a surprising departure from earlier principles. I don't
think that would be only a temporary work-around if they do so to reduce mass. IFT-4 having no payload, they don't really need to reduce mass, so they don't need to do it at all now. Perhaps this piece of hardware gets severely damaged during flight (during hot-staging) and it is easier to build a new one for each flight than to redesign it to survive intact.
On 2024-05-25 16:23, Alain Fournier wrote:
On 2024-05-25 5:06 a.m., Niklas Holsti wrote:
-a-a [ snip ]
For IFT-4, they say that there are "operational changes including the
jettison of the Super HeavyrCOs hot-stage adapter following boostback
to reduce booster mass for the final phase of flight." What, so that
part will fall into the ocean and not be reused? This is a surprising
departure from earlier principles. Perhaps it is only a temporary
work-around.
Indeed, it is a surprising departure from earlier principles. I don't
think that would be only a temporary work-around if they do so to
reduce mass. IFT-4 having no payload, they don't really need to reduce
mass, so they don't need to do it at all now. Perhaps this piece of
hardware gets severely damaged during flight (during hot-staging) and
it is easier to build a new one for each flight than to redesign it to
survive intact.
There is some good discussion by "CSI Starbase" in this video:
https://www.youtube.com/watch?v=Ytl1efG1sBw
The main suggestion is that fixing other issues by additions to the
booster HW increased booster mass so much that the LOX header tank
capacity became insufficient for booster recovery. The header tanks are already built for the next few boosters and cannot easily be made
larger. Discarding the hot-stage adapter, to reduce mass, may thus be a work-around for this header-tank issue, and may not be needed for future boosters with larger LOX header tanks.
The video also presents evidence that the hot-stage adapter actually
tore itself loose during the last minutes of IFT-3 booster flight. This
may have been a factor in the booster's attitude-control problems during
its return.
On 2024-06-04 5:51 a.m., Niklas Holsti wrote:
On 2024-05-25 16:23, Alain Fournier wrote:
On 2024-05-25 5:06 a.m., Niklas Holsti wrote:
-a-a [ snip ]
For IFT-4, they say that there are "operational changes including the >>>> jettison of the Super HeavyrCOs hot-stage adapter following boostback to >>>> reduce booster mass for the final phase of flight." What, so that part >>>> will fall into the ocean and not be reused? This is a surprising
departure from earlier principles. Perhaps it is only a temporary
work-around.
Indeed, it is a surprising departure from earlier principles. I don't
think that would be only a temporary work-around if they do so to reduce >>> mass. IFT-4 having no payload, they don't really need to reduce mass, so >>> they don't need to do it at all now. Perhaps this piece of hardware gets >>> severely damaged during flight (during hot-staging) and it is easier to >>> build a new one for each flight than to redesign it to survive intact.
There is some good discussion by "CSI Starbase" in this video:
https://www.youtube.com/watch?v=Ytl1efG1sBw
The main suggestion is that fixing other issues by additions to the booster >> HW increased booster mass so much that the LOX header tank capacity became >> insufficient for booster recovery. The header tanks are already built for >> the next few boosters and cannot easily be made larger. Discarding the
hot-stage adapter, to reduce mass, may thus be a work-around for this
header-tank issue, and may not be needed for future boosters with larger
LOX header tanks.
The video also presents evidence that the hot-stage adapter actually tore >> itself loose during the last minutes of IFT-3 booster flight. This may have >> been a factor in the booster's attitude-control problems during its return.
Thank you. The "CSI Starbase" video is cool.
Alain Fournier
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