#### Thork

##### NASA Assumptions
« on: April 26, 2016, 10:36:17 AM »
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890005752.pdf

The very first line of the summary (page 7 after the contents) sums up how NASA do their aircraft calcs. What an interesting set of assumptions to make.
« Last Edit: April 26, 2016, 10:38:37 AM by Dr David Thork »

#### garygreen

• 1217
##### Re: NASA Assumptions
« Reply #1 on: April 26, 2016, 02:26:37 PM »
"This report documents the derivation and definition of a linear aircraft model for a rigid aircraft of constant mass flying over a fiat, non-rotating earth."

The model is also simplified to aircraft of constant mass, but I don't think NASA means to imply that they have airplanes that consume no fuel.  Unless this paper was written entirely for NASA's imaginary fleet of gliders?
Go FLIP yourself in a MUTHAFLIPPIN SACK

#### Thork

##### Re: NASA Assumptions
« Reply #2 on: April 27, 2016, 06:22:07 AM »
Constant mass is likely taking the starting weight with fuel, take the end weight, add together and divide by two for the average. It doesn't necessarily say they assume no fuel. Just that there is an average assumed flight mass.

#### Rekt

• 136
##### Re: NASA Assumptions
« Reply #3 on: January 26, 2017, 02:41:49 PM »
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890005752.pdf

The very first line of the summary (page 7 after the contents) sums up how NASA do their aircraft calcs. What an interesting set of assumptions to make.
It's for simplification of calculations. They could account, it's just not worth it.

#### Flatout

• 238
##### Re: NASA Assumptions
« Reply #4 on: January 28, 2017, 04:28:54 AM »
To linearize a non-linear flight model for the purpose of simplification,  you have to assume those criteria otherwise it would no longer be LINEAR.  Linear algebra is used make approximations of nonlinear models.   If the mass changes the calculations are no longer linear.   If the vector of gravity changes via a spherical earth it wouldn't be LINEAR.   A flat plane and constant mass are demands to linearize the math.   This paper is articulating the process used to linearize the model for quicker approximations.  Those that are using this paper as a justification for a flat earth have no flipping idea what they are reading or understand linear algebra.   If flight happened with things of constant mass on a flat plane then the linear model would be the only one that existed.   There wouldn't be papers about the process of linearization.

The flat earth community looks like total nimwits when they use this paper as proof that NASA doesn't accommodate for a spherical earth.
« Last Edit: January 28, 2017, 04:43:32 AM by Flatout »