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The Setup

I magnetically anchor myself to the floor of the ISS. (yes I know there's no "floor", any wall will do)

Then, I fire a 5-round burst out the airlock.

The Question

Can the recoil from this action significantly alter the rotation of the ISS in any measure, or is this too weak to have a noticeable effect?

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    $\begingroup$ This is pure physics question. As such, I see it better suited for Physics.SE $\endgroup$
    – L.Dutch ♦
    Jun 27, 2018 at 5:10
  • $\begingroup$ not worldbuilding, stroy based. $\endgroup$
    – Trish
    Jun 27, 2018 at 8:33
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    $\begingroup$ "I magnetically anchor myself to the floor of the ISS". You know it's aluminium, right? Also, read this: what-if.xkcd.com/21 $\endgroup$
    – Madlozoz
    Jun 27, 2018 at 8:52
  • $\begingroup$ Orbital rotation or own rotation? $\endgroup$
    – Alexander
    Jun 27, 2018 at 18:08

1 Answer 1

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Let me analyse this for you: You anchor yourself to the station. So your weight is now in the ballpark of $m_1=420\times 10^3\text{kg}$. The shot bullets are about $m_2=8\times 10^{-3}\text{kg}$ each and travel at $v_2=710 \frac {\text m} {\text s}$.

Insert these into these:

  1. $F_1=5\times F_2=m_1\times a_1 = m_1\times\frac {dv_1}{dt_1}$
  2. $F_2=m_2\frac {dv_2}{dt_2}$

Assume $dt_2=0.1\text s$, $dt_1=5\times dt_2$ and do some simple math that I won't give here and you get...

  1. $dv_1=\frac{5\frac{8\times10^{-3}}{420\times10^3}\frac{710 \frac {\text m} {\text s}}{0.1\text s}}{5 \times 0.1\text s}=0.00135\frac {m}{s}$

Up to here, only the numeric value of the change in speed was relevant, NOT the direction (vector) at all. To see how this affects the rotation, you'll have to insert some data: your own position from that rotational axis and the vectors of both the shot and the station.

  1. $\vec {v_1}=\vec\omega_1\times\vec{r_2}$
  2. $\vec{d\omega_1}=\frac{\vec {dv_1}} {|\vec{r_2}|}$

This change in orbit (which is dependant on the part of $\vec{v_1}$ along its orbit only) and rotation ($\vec {d\omega}$) is tiny and the next automated correction burn will fix more than this.

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  • $\begingroup$ 0.00135 m/s = 1 millimeter per second = 3.6 meters per hour. This was for entire weight of the station, and rotation computation should probably use lower weight (maybe half?), leading to even more speed. If station is 100 meters wide, this is enough rotation to be noticeable. But I assume station has GYROSCOPES to compensate for people pushing off the walls as they move around the station, and they will probably cancel out most of the rotation from AK-47 rounds. $\endgroup$
    – Bald Bear
    Jun 27, 2018 at 14:47
  • $\begingroup$ @BaldBear that's not how physics work. All or nothing. The further out you shoot, the less impact it has. $\endgroup$
    – Trish
    Jun 27, 2018 at 15:42
  • $\begingroup$ Please do not vote to close a question AND answer it. First, you've voted to close the question (thus stating that "this question should not be answered) but then gone and posted an answer. This sets a bad example. Second, you have created an unfair advantage using your vote to close privileges; Since the question is now closed, your answer will be the ONLY answer on the question (as other potential candidates have now been locked out of answering). This is gaming the system. $\endgroup$
    – Aify
    Jun 27, 2018 at 16:41
  • $\begingroup$ worldbuilding.meta.stackexchange.com/questions/3120/… $\endgroup$
    – Aify
    Jun 27, 2018 at 16:42

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