7
$\begingroup$

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.

$\endgroup$
7
  • 4
    $\begingroup$ 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/… $\endgroup$ Mar 11 at 20:00
  • 1
    $\begingroup$ Moonport says each shoe is 0.3x2.3 meters with 57 shoes per track. (Page 274) $\endgroup$
    – Ludo
    Mar 11 at 22:16
  • 1
    $\begingroup$ @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. $\endgroup$ Mar 11 at 22:38
  • 5
    $\begingroup$ 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. $\endgroup$ Mar 11 at 22:41
  • 1
    $\begingroup$ @OrganicMarble I'll take a stab at answering, since I think we have enough info (going to be borrowing that photo, it's great) $\endgroup$ Mar 12 at 9:38

1 Answer 1

6
$\begingroup$

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
Road racing bicycle 90
Mountain bicycle 40
Adult elephant 35
Passenger car 30

Unless my math above is heinously wrong, the ground pressure would seem to be within the range of some common vehicles.

$\endgroup$
3
  • 2
    $\begingroup$ I think you need to add the weight of ML-1 as well $\endgroup$
    – Ludo
    Mar 12 at 10:01
  • 2
    $\begingroup$ @Ludo ah, there's my heinously wrong math! Also, thanks for the mention of Moonport. 1 moment re-doing some math (at least those maximum capacity calculations should be right) $\endgroup$ Mar 12 at 10:07
  • 4
    $\begingroup$ Turns out that it puts it a lot closer to the maximum capacity (which makes sense), which would explain why it seemed a bit ... light ... when I was doing the math. $\endgroup$ Mar 12 at 10:11

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.