documentclass[11pt,oneside]{book}
usepackage{titlesec}
% Below "section" can be replaced with "subsection" and "subsubsection"
% in order to customize the corresponding headings. "bch" - Bitstream
% Charter, "b" - bold.
titleformat{section}[hang]
{usefont{T1}{bch}{b}{n}selectfont}
{}    % label
{0em} % horizontal separation between label and title body
{hspace{-0.4pt}Large thesectionhspace{0.6em}} % before-code
[] % after-code

titleformat
{chapter}                       % command
[display]                        % shape
{normalfonthugebfseries}      % format
{chaptertitlename thechapter} % label
{20pt}                           % sep
{Huge}[vspace{2ex}titlerule]  % before-code

begin{document}
maketitle
chapter*{Abstract}
Lorem Ipsum etc. etc.
end{document}

documentclass[11pt,oneside]{book}
usepackage{titlesec}
% Below "section" can be replaced with "subsection" and "subsubsection"
% in order to customize the corresponding headings. "bch" - Bitstream
% Charter, "b" - bold.
titleformat{section}[hang]
{usefont{T1}{bch}{b}{n}selectfont}
{}    % label
{0em} % horizontal separation between label and title body
{hspace{-0.4pt}Large thesectionhspace{0.6em}} % before-code
[] % after-code

titleformat
{chapter}                       % command
[display]                        % shape
{normalfonthugebfseries}      % format
{chaptertitlename thechapter} % label
{20pt}                           % sep
{Huge}[vspace{2ex}titlerule]  % before-code

titleformat
{name=chapter,numberless}                       % command
[display]                        % shape
{normalfonthugebfseries}      % format
{} % label
{0pt}                           % sep
{Huge}[vspace{2ex}titlerule]  % before-code    %% adjust 2ex here as you want.

begin{document}
%maketitle
chapter*{Abstract}
Lorem Ipsum etc. etc.
end{document}

titlespacing*{chapter} {0pt}{50pt}{40pt}

titlespacing*{name=chapter,numberless} {0pt}{50pt}{40pt}