Pam Melroy, Former NASA Deputy Administrator, Space Shuttle Commander, and three-time Shuttle astronaut, joins me to talk about space policy past, present, and future. We talk about the most critical decisions and moments during her time as Deputy Administrator under Administrator Bill Nelson, and her thoughts on the Isaacman-era space policy from Ignition to Commercial LEO, and what to do about Mars Sample Return.

This episode of Main Engine Cut Off is brought to you by 32 executive producers—Steve, Lee, Russell, Stealth Julian, Warren, Miles O’Brien, Josh from Impulse, Joel, David, Natasha Tsakos, Joakim, Will and Lars from Agile, Frank, Better Every Day Studios, Tim Dodd (the Everyday Astronaut!), Donald, The Astrogators at SEE, Jan, Joonas, Pat, Matt, Kris, Fred, Theo and Violet, Ryan, and four anonymous—and hundreds of supporters.

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Artemis II completed their lunar flyby yesterday, and it was epic on all levels. Paul Fjeld and I discuss that and many other topics related to Artemis, Apollo, and human spaceflight.

This episode of Main Engine Cut Off is brought to you by 32 executive producers—Ryan, Tim Dodd (the Everyday Astronaut!), Will and Lars from Agile, David, Better Every Day Studios, Kris, Stealth Julian, Joonas, Russell, Warren, Jan, Natasha Tsakos, Steve, Pat, The Astrogators at SEE, Fred, Donald, Miles O’Brien, Matt, Josh from Impulse, Frank, Lee, Joakim, Joel, Theo and Violet, and four anonymous—and hundreds of supporters.

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Artemis II is underway with a spectacular first day.

This episode of Main Engine Cut Off is brought to you by 32 executive producers—Donald, Matt, David, Joel, Frank, Better Every Day Studios, Natasha Tsakos, Tim Dodd (the Everyday Astronaut!), Lee, Fred, Will and Lars from Agile, Ryan, Warren, The Astrogators at SEE, Pat, Joakim, Miles O’Brien, Steve, Jan, Stealth Julian, Kris, Theo and Violet, Russell, Josh from Impulse, Joonas, and four anonymous—and hundreds of supporters.

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There was a lot of news in NASA’s Ignition event last week, and I break down what actually matters: not whether Jared Isaacman’s timelines are realistic, but how this new roadmap strips away architectural dependencies and forces the real bottlenecks into the open. I talk through Gateway’s cancellation, the possible path away from SLS and ICPS, what this means for lunar landers and international partners, and why NASA’s new philosophy feels so different from the past.

This episode of Main Engine Cut Off is brought to you by 32 executive producers—Steve, Joel, Kris, Josh from Impulse, Will and Lars from Agile, Warren, Natasha Tsakos, Tim Dodd (the Everyday Astronaut!), Lee, Joonas, Better Every Day Studios, Russell, Fred, David, Donald, Frank, Miles O’Brien, Jan, Joakim, The Astrogators at SEE, Stealth Julian, Theo and Violet, Matt, Pat, Ryan, and four anonymous—and hundreds of supporters.

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Tom Mueller, Founder and CEO of Impulse Space, joins me to catch up on the company’s progress and plans—3 Mira missions flown, Helios soon to fly, $525M raised, new defense contracts, a lunar lander concept, and a new Colorado facility.

This episode of Main Engine Cut Off is brought to you by 33 executive producers—Joel, Tim Dodd (the Everyday Astronaut!), Warren, Steve, Ryan, Will and Lars from Agile, Natasha Tsakos, Russell, Joakim, Theo and Violet, The Astrogators at SEE, Matt, Lee, Donald, Heiko, Better Every Day Studios, Josh from Impulse, Miles O’Brien, Stealth Julian, David, Joonas, Kris, Frank, Jan, Fred, Pat, and four anonymous—and hundreds of supporters.

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NASA Administrator Jared Isaacman announced a sweeping roadmap change to the Artemis program this morning—seemingly cancelling the EUS, Gateway, and all SLS upgrades, and instead pursuing the once-and-future annual launch cadence of SLS.

This episode of Main Engine Cut Off is brought to you by 33 executive producers—David, Russell, Pat, Better Every Day Studios, Joonas, Josh from Impulse, Theo and Violet, Steve, Jan, Will and Lars from Agile, Miles O’Brien, Kris, Fred, Stealth Julian, Frank, Joakim, Ryan, Warren, Matt, The Astrogators at SEE, Joel, Lee, Tim Dodd (the Everyday Astronaut!), Donald, Natasha Tsakos, Heiko, and four anonymous—and hundreds of supporters.

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Loren Grush, of Bloomberg, joins me to talk about SpaceX’s acquisition of xAI, its preparation for a potential IPO, Blue Origin’s cancellation of New Shepard and their recent momentum, and the delay to Artemis II following its first wet dress rehearsal.

This episode of Main Engine Cut Off is brought to you by 33 executive producers—David, Natasha Tsakos, Stealth Julian, Warren, Joakim, Tim Dodd (the Everyday Astronaut!), Miles O’Brien, Pat, Better Every Day Studios, Will and Lars from Agile, The Astrogators at SEE, Steve, Joonas, Frank, Fred, Heiko, Donald, Lee, Russell, Kris, Ryan, Theo and Violet, Joel, Matt, Jan, Josh from Impulse, and four anonymous—and hundreds of supporters.

Topics

• SpaceX Acquires xAI as Musk Prepares for Mega IPO - Bloomberg
• SpaceX-xAI Deal Blurs Musk’s Once-Clear Space Exploration Mission - Bloomberg
• Loren Brichter, a High Priest of App Design - WSJ
• Blue Origin to Pause New Shepard Flights for No Less Than Two Years | Blue Origin
• NASA Conducts Artemis II Fuel Test, Eyes March for Launch Opportunity   - NASA

The Show

• Like the show? Support the show on Patreon or Substack!
• Email your thoughts, comments, and questions to [email protected]
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• Artwork photo by NASA/John Kraus
• Work with me and my design and development agency: Pine Works

Artemis II is on the pad, and I can’t stop thinking about it. So I guess listen to me think in the open? Also, a ton of Blue Origin news—the next flight of New Glenn will feature a flown booster, they’ve announced constellation plans under the name TeraWave, and Tory Bruno has left ULA to join the team at Blue.

This episode of Main Engine Cut Off is brought to you by 33 executive producers—Matt, Fred, Will and Lars from Agile, Kris, Lee, Jan, Frank, Miles O’Brien, Josh from Impulse, Theo and Violet, Ryan, Joakim, Stealth Julian, Heiko, Tim Dodd (the Everyday Astronaut!), Better Every Day Studios, Joel, Steve, Joonas, The Astrogators at SEE, Pat, Warren, Natasha Tsakos, Russell, David, Donald, and four anonymous—and hundreds of supporters.

Topics

• NASA’s Moonbound Artemis II Rocket Reaches Launch Pad - NASA
• Final Steps Underway for NASA’s First Crewed Artemis Moon Mission - NASA
• Is Orion’s heat shield really safe? New NASA chief conducts final review on eve of flight. - Ars Technica
• Blue Origin makes impressive strides with reuse—next launch will refly booster - Ars Technica
• New Glenn-3 to Launch AST SpaceMobile’s BlueBird Satellite | Blue Origin
• Blue Origin on X: “Our lunar lander is headed to the Lone Star State! ⭐ Blue Moon MK1 departed from Florida today, bound for @NASA_Johnson's Thermal Vacuum Chamber A, where it will undergo testing at the same facility as the Apollo spacecraft.”
• Another Jeff Bezos company has announced plans to develop a megaconstellation - Ars Technica
• First Take: What We Think Blue Origin’s TeraWave Actually Is (and Isn’t)
• In a surprise announcement, Tory Bruno is out as CEO of United Launch Alliance - Ars Technica
• Blue Origin on X: “We’re pleased to announce that @torybruno is joining Blue Origin as president, National Security, reporting to CEO Dave Limp. Tory will spearhead our newly formed National Security Group.”

The Show

• Like the show? Support the show on Patreon or Substack!
• Email your thoughts, comments, and questions to [email protected]
• Follow @WeHaveMECO
• Follow @[email protected] on Mastodon
• Listen to MECO Headlines
• Listen to Off-Nominal
• Join the Off-Nominal Discord
• Subscribe on Apple Podcasts, Overcast, Pocket Casts, Spotify, Google Play, Stitcher, TuneIn or elsewhere
• Subscribe to the Main Engine Cut Off Newsletter
• Artwork photo by Blue Origin
• Work with me and my design and development agency: Pine Works

Casey Dreier of The Planetary Society joins me to talk about the NASA FY2026 budget, the early days of the Administrator Isaacman era, and how we feel going into Artemis II.

This episode of Main Engine Cut Off is brought to you by 33 executive producers—Matt, Fred, Will and Lars from Agile, Kris, Lee, Jan, Frank, Miles O’Brien, Josh from Impulse, Theo and Violet, Ryan, Joakim, Stealth Julian, Heiko, Tim Dodd (the Everyday Astronaut!), Better Every Day Studios, Joel, Steve, Joonas, The Astrogators at SEE, Pat, Warren, Natasha Tsakos, Russell, David, Donald, and four anonymous—and hundreds of supporters.

Topics

• Casey Dreier | The Planetary Society
• The Planetary Society
• You just saved NASA's budget | The Planetary Society
• 2025 Impact Report | The Planetary Society

The Show

• Like the show? Support the show on Patreon or Substack!
• Email your thoughts, comments, and questions to [email protected]
• Follow @WeHaveMECO
• Follow @[email protected] on Mastodon
• Listen to MECO Headlines
• Listen to Off-Nominal
• Join the Off-Nominal Discord
• Subscribe on Apple Podcasts, Overcast, Pocket Casts, Spotify, Google Play, Stitcher, TuneIn or elsewhere
• Subscribe to the Main Engine Cut Off Newsletter
• Artwork photo by Blue Origin
• Work with me and my design and development agency: Pine Works

A holiday special! Enjoy this week’s episode of Headlines free. It’s an absolute monster episode—way longer than usual Headlines episodes, I promise—but it’s a great example of what you get when you support the show over at mainenginecutoff.com/support.

• NASA finally—and we really do mean it this time—has a full-time leader - Ars Technica
• Agencywide Town Hall with NASA Administrator Jared Isaacman, Friday, Dec. 19, 2025 - YouTube
• Trump commits to Moon landing by 2028, followed by a lunar outpost two years later - Ars Technica
• NASA Teams Work MAVEN Spacecraft Signal Loss - NASA Science
• NASA Continues MAVEN Spacecraft Recontact Efforts - NASA Science
• SpaceX Sets $800 Billion Valuation, Confirms 2026 IPO Plans - Bloomberg
• SpaceX $1.5 Trillion Value Target Hinges on Starlink — And Elon - Bloomberg
• SpaceX Said to Notify Employees of Quiet Period Ahead of IPO - Bloomberg
• In a surprise announcement, Tory Bruno is out as CEO of United Launch Alliance - Ars Technica
• Space Development Agency awards $3.5 billion in contracts for missile-tracking satellites - SpaceNews
• Chinese astronauts inspect debris-damaged Shenzhou-20 spacecraft during spacewalk - SpaceNews
• Space Station – Off The Earth, For The Earth
• NASA Astronaut Jonny Kim, Crewmates Return from Space Station - NASA
• After key Russian launch site is damaged, NASA accelerates Dragon supply missions - Ars Technica
• R-7 ICBM/Soyuz rocket launch facilities in Baikonur
• Launch Roundup: China, Russia, Rocket Lab, ULA join SpaceX in flying this week - NASASpaceFlight.com
• Launch Previews: Ariane 6, Falcon 9, Atlas V, and Electron launches highlight busy week - NASASpaceFlight.com
• Launch Roundup: International launches fill manifest during last full week of 2025 - NASASpaceFlight.com
• China launches 4 times in 4 days, boosting megaconstellation and surveillance assets - SpaceNews
• China launches new TJS satellite, commercial Kinetica-1 lofts 9 spacecraft - SpaceNews
• Michael Nicolls on X: “When satellite operators do not share ephemeris for their satellites, dangerously close approaches can occur in space.   A few days ago, 9 satellites were deployed from a launch from the Jiuquan Satellite Launch Center in Northwestern China. As far as we know, no coordination or…”
• China launches experimental cargo spacecraft, opaque tech demo mission and remote sensing satellite - SpaceNews
• Andrew Jones on X: “Turns out there were two male mice launched on the DEAR-5 cargo spacecraft for neuroscience research. Spacecraft is planned to operate in orbit for one year and is not rated for reentry, so it's game over at some point for the rodents. Video is prelaunch.”
• Rocket Lab launches JAXA tech demo satellite - SpaceNews
• Ariane 6 launches Galileo navigation satellites - SpaceNews
• These are the flying discs the government wants you to know about - Ars Technica
• Blue Origin flies first wheelchair user to space - SpaceNews
• Rocket Lab wraps up record launch year - SpaceNews
• Japan’s H3 suffers second-stage anomaly, QZS-5 satellite lost - SpaceNews
• Andrew Jones on X
• China launches new Guowang satellites, Long March 12A launch and landing attempt date set - SpaceNews

Keep an eye on upcoming launches with rocketlaunch.live.