Of external tanks and Starships

Iconic orange Space Shuttle external tanks and shiny SpaceX Starships are uncannily close in scale. I was fortunate to be on the team in the 1990’s that checked out and prepared the external tanks and then on the team that filled and launched them. I could not have guessed that 23 years into my career at NASA I would also be on a team looking at refilling propellant tanks in space (my contribution being to connect the new technology with NASA budgets). Refueling in space is now the challenge that awaits the SpaceX Starship and NASA.

From Starship wikipedia.

August 8, 2005 Myself at the Space Shuttle Atlantis in the VAB (which was eventually de-stacked as the order of the flights after the loss of Columbia shifted around). Credit: Edgar Zapata, zapatatalksnasa.com

I had a chance to crawl around inside Space Shuttle external tanks (and orbiters, and once even inside a solid rocket motor-filled). I took the picture below inside a tank, in the “intertank”, the space between the forward liquid oxygen tank and the aft liquid hydrogen tank. I recall the particular picture well, for the special care I had to have inside the tank that day. This was not because of being inside a multi-million-dollar piece of flight hardware where not watching my step could easily cause some damage. Not at all. Being inside flight hardware was by then a rather familiar if always conscious affair. Instead, my trepidation was because of the particular camera I held this day – one of the first ever digital cameras, and naturally being NASA, we spared no expense. In look and feel it was similar to a modern DSLR with a long lens – except this was 1991 and such things then were from the future. It was $100,000 worth of technology from the future. Except as is visible from the photo, it has about the quality anyone gets today on a cell phone. That is from a cell phone that comes free with the monthly plan. The lowest end cell phone. With the least expensive plan.

Flash forward and it’s now nearly the tenth anniversary of the NASA Propellant Depot Study. The SpaceX Starship and refueling in space are (barring protests) poised to help lead the way to deep space exploration. Perhaps soon we will see more of just what is inside the Starships, apart from figures of the basic layout of liquid oxygen or liquid methane tanks and some feedlines. Perhaps we will see the diffusers, slosh baffles, crawl spaces and vent valves and more. Perhaps we will also see that like that $100,000-dollar digital camera, things have improved.

(1) Above, late 1991, External Tank ET-43 interior, the “intertank” and (2) below, photo rear. The blocks with the red numbers are light-weight but strong foam blocks / steps placed only to allow walking atop the dome of the tank below. These are removed before flight. Credit: Edgar Zapata, zapatatalksnasa.com

Pictures above, left to right, (1) The scale of the Space Shuttle external tank, (2) inside an external tank (with annotations about leak checks), (3) rear of prior photo, (4) atop the Space Shuttle LOX storage sphere at Pad A in 1996 (a beautiful day for a walk down!) and (5) a screen capture of the launch computer while loading the external tank September 12, 1992, for STS-47 at Pad B with Endeavour (first launch attempt). Credits: Edgar Zapata, zapatatalksnasa.com

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