# understanding how to rotate arrows in tikz

I have seen the post on the rotation of arrows and one of the post is mine. However, I don't understand how to do accomplish it myself. For instance, I am making a picture of Hohmann transfer where on the orbits I want triangular arrows pointing counter clockwise and "v" type arrow on the transfer.

This part is completed:

My goals is to put on the outer orbit 2 of the triangle arrows: one at 30 degrees and the other at 210 degrees.

The inner orbit 2 triangular arrows at 135 and 315 degrees.


For the Hohmann transfer I want to put 2 arrows: one about 40 percent of the curve and the other 70 percent. However, I also am not sure how to create an arc that goes between the two orbits and arrives at (-3,0). I tried the arc command but that was just guessing and it wasn't looking pretty.

For some reason, only one arrow shows up on the Hohmann transfer. I specified at 0.15 and 0.35.

\documentclass[11pt]{article}
\usepackage{tikz, tikz-qtree,kurier, pgfplots}
\usetikzlibrary{arrows, decorations.markings, calc, fadings, decorations.pathreplacing, patterns, decorations.pathmorphing, positioning}
\begin{document}
\begin{center}
\begin{tikzpicture}[line join = round, line cap = round, >=triangle 45]
\filldraw[orange!60!yellow!50!red, opacity = .75] (0,0) circle (.25cm);
\draw (0,0) -- (4,0);
\draw (0,0) -- (3,3);
\begin{scope}[decoration = {markings, mark = at position 0.0416 with {\arrow{>}}, mark = at
position 0.58333 with {\arrow{>}}, }]
\draw[postaction = decorate] (0,0) circle (3cm);
\end{scope}
\begin{scope}[decoration = {markings, mark = at position 0.375 with {\arrow{>}}, mark = at
position 0.875 with {\arrow{>}}, }]
\draw[postaction = decorate] (0,0) circle (1.5cm);
\end{scope}
\filldraw[red] (2.12132,2.12132) circle (.075cm);
\begin{scope}[decoration = {markings, mark = at position 1 with {\arrow{>}}, }]
\draw[postaction = decorate] (1,0) arc (0:45:1cm) node[scale = .75, fill = white,
inner sep = .05cm, circle] at (.5,.2) {$\alpha$};
\end{scope}
\begin{scope}[decoration = {markings, mark = at position 0.15 with {\arrow{>}}, mark = at
position 0.35 with {arrow{>}}, }]
\clip (-3,0) rectangle (1.5,3);
\draw[postaction = decorate] (-.75,0) ellipse (2.25cm and 2.4cm);
\end{scope}
\draw[fill = white] (-3,0) circle (.075cm);
\filldraw[top color = green!75!blue, bottom color = blue!40!green] (1.5,0) circle (.15cm);
\end{tikzpicture}
\end{center}
\end{document}

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For the second question (arrows at 15 and 210 degrees), you can use a decoration: \begin{scope}[decoration={ markings, mark=at position 0.0416 with {\arrow{>}}, mark=at position 0.58333 with {\arrow{>}}, }] \draw[postaction=decorate] (0,0) circle (3cm); \end{scope} –  Gonzalo Medina Mar 29 '13 at 3:22
@GonzaloMedina Can you explain the position choice values? –  dustin Mar 29 '13 at 3:33
@GonzaloMedina percentage of 360 I suspect now. –  dustin Mar 29 '13 at 3:49
@GonzaloMedina I have accomplished everything except for putting two arrows on the transfer orbit. I specified 0.15 and 0.35. I am only clipping the lower half of the ellipse as well. –  dustin Mar 29 '13 at 4:22
You forgot \  before arrow here position 0.35 with {arrow{>}}, }] –  Alain Matthes Mar 29 '13 at 8:00

You can use the ellipse radii and start stop angles to use an arc. Also I've cleaned up a bit.

\documentclass[tikz]{standalone}
\usetikzlibrary{arrows, decorations.markings}
\begin{document}

\begin{tikzpicture}[>=triangle 45,
mydeco/.style = {decoration = {markings,
mark = at position #1 with {\arrow{>}}}
}
]
\filldraw[orange!60!yellow!50!red, opacity = .75] (0,0) circle (.25cm);
\draw (0,0) -- (4,0);
\draw (0,0) -- (3,3);
\draw[postaction = {mydeco=0.0416 ,decorate},
postaction = {mydeco=0.58333 ,decorate}] (0,0) circle (3cm);

\draw[postaction = {mydeco=0.375 ,decorate},
postaction = {mydeco=0.875 ,decorate}] (0,0) circle (1.5cm);

\filldraw[red] (2.12132,2.12132) circle (.075cm);
\draw[->] (1,0) arc (0:45:1cm)
node[fill = white,inner sep = .05cm] at (.5,.2) {$\scriptstyle\alpha$};

\draw[postaction = {mydeco=0.15 ,decorate},
postaction = {mydeco=0.35 ,decorate}] (0:1.5) arc (0:180:2.25cm and 2.4cm);

\draw[fill = white] (-3,0) circle (.075cm);

\filldraw[top color = green!75!blue, bottom color = blue!40!green] (1.5,0) circle (.15cm);

\end{tikzpicture}

\end{document}


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