Apollo F-1 engines gained measurable weight due to thermal protection charring during flight
the verdict
REFUTED
the evidence says no
refutedsupported
the weight of evidence
0 sources for · 1 against
AS REPORTEDno primary record reached; this is what the reporting says
Retrieved technical discussions demonstrate that the apparent weight gain of the Apollo F-1 engines during flight was due to trapped residual propellants rather than thermal protection charring.
# Did the Apollo F-1 engines gain weight during flight?
Tags: launch, apollo-program, engine-design, saturn-v
- Score: 12
- Views: 1432
- Answers: 2
- Answered: yes
- Asked by: ForgeMonkey (7160 rep)
- Asked: 2015-06-12
- Edited: 2015-06-12
- Site: space
## Question
I was browsing through Wikipedia when I came across this infographic on the Rocketdyne F-1. It gives the engine dry weight as 18,500 pounds, and the engine burnout weight as 20,180 pounds, meaning the engine somehow gains 1,680 pounds in-flight.
Can anyone confirm what causes the weight discrepancy? 1,680 pounds of soot stuck to the engine bell seems excessive.
## Answers
### Answer by Organic Marble (score: 9 [ACCEPTED])
The difference in the engine weights is due to trapped propellant. Referring to the Saturn V Flight Manual for SA-503, Figure 2-21, we can see that the residual propellant in the 5 engines is 2160 lbs LOX and 6585 lbs RP-1. Dividing the sum of these numbers (8745) by 5 we get a per-engine trapped prop mass of 1749 which is probably close enough to the 1680 lbs/engine shown in the graphic above.
I have reproduced the appropriate table for your convenience below.
### Answer by Rikki-Tikki-Tavi