Timeline for Distance from ground to start suicide burn with initial height
Current License: CC BY-SA 4.0
6 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| May 25, 2019 at 6:19 | vote | accept | dmoody256 | ||
| May 25, 2019 at 6:19 | comment | added | dmoody256 | OK, that clears it up, I like your answer because it intuitively uses the delta V in both free fall and burn to relate the distances to the accelerations. It makes more sense the relationship rather than the plug and chug deduction I came up with. Thanks! | |
| May 25, 2019 at 5:13 | comment | added | Cort Ammon | @dmoody256 As for directions for a and g, your approach is consistent, especially in 1d. I do a lot of work in 3d, where is it very convenient to think of vectors as made up of a positive magnitude and a unit-vector that specifies the direction. Since I was going for a more intuitive approach, I naturally used the vector notation that I am most comfortable with -- for better or for worse. | |
| May 25, 2019 at 5:10 | comment | added | Cort Ammon | @dmoody256 Ahh, those numbers will help for clarification. If I were to assign the variables as I did in my work, I would say $g=9.8 m/s$, $a_b=0.2 m/s$ and $h=1000 m$, yielding $d_b = \frac{9.8}{9.8+0.2}\cdot 1000 = 980 m$. If you labeled the variables differently, you may have to tweak the approach I took. | |
| May 25, 2019 at 4:56 | comment | added | dmoody256 | I assumed down is negative, so g = -9.8m/s^2. I plugged some numbers in to test, so let the rocket start at h = 1000m, and be able to provide 10m/s^2 thrust, which gives a net upwards acceleration of 0.2m/s^2 (10 - 9.8). Plugging those into your equation, I get 1020.8333m, which is higher than the initial height so I am a bit confused. I think your answer is right but I don't understand in your deduction where the a and g assign different coordinate systems, e.g your g assumes down is positive and your a assumes up is positive. My question was not explicit about coordinate systems either. | |
| May 25, 2019 at 2:50 | history | answered | Cort Ammon | CC BY-SA 4.0 |