James Webb Space Telescope’s Aft Momentum Flap Deployed

Webb Aft Momentum Flap Deployment

Webb Aft Momentum Flap deployment. Credit: NASA’s Goddard Space Flight Center Conceptual Image Lab

Shortly after 9 a.m. EST today (December 30, 2021), the Webb team completed deployment of the observatory’s aft momentum flap. In a process that took about eight minutes, engineers released the flap’s hold-down devices, and a spring brought the flap into its final position.

The aft momentum flap helps minimize the fuel engineers will need to use throughout Webb’s lifetime, by helping to maintain the observatory’s orientation in orbit. As photons of sunlight hit the large sunshield surface, they will exert pressure on the sunshield, and if not properly balanced, this solar pressure would cause rotations of the observatory that must be accommodated by its reaction wheels. The aft momentum flap will sail on the pressure of these photons, balancing the sunshield and keeping the observatory steady.

Just as a ship’s mast must be set in position and the rigging established before the ship unfurls its sails, Webb’s pallet structures, momentum flap, and mid-booms will soon all be in place for Webb’s silver sunshield to unfold. The next steps in Webb’s planned deployment timeline are outlined here.

3 Comments on "James Webb Space Telescope’s Aft Momentum Flap Deployed"

  1. Way Cool

  2. Eagerly waiting for the first images

  3. William Jamieson | January 4, 2022 at 8:29 am | Reply

    I am not a big supporter of NASA,as any way you look at this, they will be the catalyst when it comes to weaponizing space.That alone is sacrilege,but they following orders unlike any government agencies.
    The Charles Webb scope is a different story with me.I am excited over the Webb,although I would have named it “Carl Sagan” after all he is the one that excited us baby boomers. I am an engineer and never dreamt the Webb would have gotten this far with no problems, and most of the high hurdles have been cleared.I want to commend NASA with this stellar performance,but don’t understand why they did not leave the Saran Wrap deflectors deployed and tensioned. I would drop the Mars mission, as there is no practical use for it.
    Take the high ground and explore, to where no humans are involved. Great Job.

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