header.tex

% boxes
\usepackage{mdframed}
\newenvironment{inbox}{\begin{mdframed}\small\setlength{\parskip}{1ex}}{\end{mdframed}}
\newcommand{\newpageon}[1]{\newpage}
\newcommand{\pagebreakon}[1]{\pagebreak}

% make an environment called "abstract" that ignores its contents,
% because the book class does not provide an "abstract" environment
\usepackage{comment}
\excludecomment{abstract}

% do not show leading "Figure n" or "Table n"
\usepackage{caption}
\captionsetup[figure]{labelformat=empty,font=small}
\captionsetup[table]{labelformat=empty}

% to adapt list appearance in "Bibliographic Note"
\usepackage{enumitem}

% set default figure placement to !htbp
\makeatletter
\def\fps@figure{!htbp}
\makeatother

% footnotes with stars
\usepackage{alphalph}
\makeatletter
\newcommand*{\fnsymbolsingle}[1]{\ensuremath{\ifcase#1\or *\else\@ctrerr\fi}}
\makeatother
\newalphalph{\fnsymbolmult}[mult]{\fnsymbolsingle}{}
\renewcommand*{\thefootnote}{\fnsymbolmult{\value{footnote}}}

% reset footnotes after starting a new part (important on page 136)
\makeatletter
\@addtoreset{footnote}{part}
\makeatother

% set font of verbatim environments
% https://tex.stackexchange.com/questions/120633/change-typeface-of-verbatim-environment/120694#120694
\makeatletter
\newcommand{\verbatimfont}[1]{\def\verbatim@font{#1}}%
\makeatother
\verbatimfont{\scriptsize\ttfamily}

% to reset chapters to root (startatroot)
\usepackage{bookmark}

% headers
\usepackage{scrlayer-scrpage}
\clearpairofpagestyles
\lehead{\thepage\ \MakeUppercase{Computers in Spaceflight: The NASA Experience}}
\rohead{\MakeUppercase{\leftmark}\ \thepage}
\setkomafont{pagehead}{\normalfont \scriptsize \bfseries}
%% omit "chapter n: " prefix in front of chapter name in header
%% https://tex.stackexchange.com/questions/228362/get-sectionmark-in-fancyhdr-without-chapter-number/228363#228363
\renewcommand{\chaptermark}[1]{\markboth{#1}{}}
\renewcommand{\partmark}[1]{\markboth{#1}{}}

% indentation of new paragraphs
\setlength{\parindent}{2em}
% space between lines
\linespread{0.8}
% do not "stretch" page content to fill page
\raggedbottom

% for Numberstring
\usepackage{fmtcount}

\RedeclareSectionCommand[
    beforeskip=0em
]{part}
\renewcommand*{\partformat}{\partname~\Numberstring{part}:}
\renewcommand*\raggedpart{\raggedright}
\addtokomafont{partnumber}{\normalfont}
\makeatletter
\renewcommand*{\partheadmidvskip}{ }
\renewcommand{\partheadendvskip}{\vskip\@tempskipa\hrule\vspace{1.5em}}
\makeatother
\renewcommand{\partheademptypage}{}

\RedeclareSectionCommand[
    innerskip=1em
]{chapter}
\renewcommand*{\chapterformat}{\quad \thechapter}
\addtokomafont{chapter}{\normalfont}
\makeatletter
\renewcommand*{\chapterheadendvskip}{\vskip\@tempskipa\newpage}
\makeatother

\setkomafont{section}{\normalfont\normalsize\bfseries\MakeUppercase}
\setkomafont{subsection}{\normalfont\normalsize\bfseries}
\setkomafont{subsubsection}{\normalfont\bfseries\centering}