# Crawler-transporter's ground pressure?

How many PSI does the CT-2 crawler carrying the Artemis I rocket exert on the ground?
How does that compare to more conventional vehicles?

NASA's fact sheet mentions relevant weights, and that each corner of the crawler has a two-belt truck, but it omits the footprint of the 8 belts.

• There is a possible upper bound stated in a test of the crawlerway foundation. One shoe in the track is 1620 in^2 and is required to carry up to 500,000 lb, which works out to about 300 psi. nasa.gov/missions/shuttle/crawler_shoes.html jonesedmunds.com/portfolio-works/… Mar 11 at 20:00
• Moonport says each shoe is 0.3x2.3 meters with 57 shoes per track. (Page 274)
– Ludo
Mar 11 at 22:16
• @Ludo the link I cited (assuming I converted it right, always a shaky assumption) gives 0.46 x 2.3 meters. Not sure why the discrepancy, both are NASA sources. I know the shoes were replaced at least once, but I assumed the "footprint" didn't change, that could also be wrong. Mar 11 at 22:38
• Here's my best personal photo of a crawler track. I count 22 shoes on the ground. i.imgur.com/BQEJuRm.jpg Taken in 2008. Mar 11 at 22:41
• @OrganicMarble I'll take a stab at answering, since I think we have enough info (going to be borrowing that photo, it's great) Mar 12 at 9:38

From differing sources, the shoes are either 7.5 feet x 1.5 feet (2.286 meters x 0.4572 meters) or 0.3 meters x 2.3 meters (7.54593 feet x 0.984252 feet), for an area between 1620 in2 and 1070 in2 which is a bit of a range, but workable.

Given a 500,000 lb load test, that gives an upper bound to the between 308 PSI and 467 PSI, but that's the design per-shoe and not the capacity or weight of the system.

According to this page, the crawler itself weighs "Approximately 6.6 million pounds", with a maximum load of 18 million pounds, while this sheet lists the Artemis I launch vehicle at "Approximately 3.5 million pounds" and ML-1 (Mobile Launcher-1) as "Approximately 11.3 million pounds". That gives us a total weight of 21.4 million pounds for Artemis 1, with a max design weight of 24.6 million pounds.

Thanks to Organic Marble for the wonderful picture of the crawler, where I agree with his count of 22 shoes on the ground at a time. With 22 shoes per track and 8 tracks per crawler, that gives 176 total shoes.

Shoe area Artemis I At Maximum Capacity
1620 in2 75.1 PSI 86.3 PSI
1070 in2 114 PSI 131 PSI

Taking a few of the the examples of ground pressures from the question,

Object Ground pressure (psi)
Stiletto heel 471