There are several options in providing for child support of minor children when one of the parents is in the military. One option is the traditional method of pursuing court-ordered support through the state court with jurisdiction. An issue that may pop up in this instance is the Servicemember's Civil Relief Act (SCRA) which mandates a stay on civil matters while a servicemember is on active duty. A servicemember can waive this statutory protection in writing and proceed with any civil matter, including family law issues, at their discretion. Another option is to reach an agreement on support. Written support agreements can be enforced through the military or the state court with jurisdiction.
A final option where there is no agreement and the servicemember has not elected to proceed with a state court child support proceeding is for the relevant branch of military to establish an interim support amount based on their regulations. All branches of the military maintain regulations that require a duty of support by the servicemember to their family/dependents. Most branches of the military have established support requirements that are tied to the number of dependents requiring support (spouse and minor children) and their gross pay and/or Basic Allowance for Housing (BAH). See the links below or specific information on how support is calculated by the various branches of the military in the absence of a court order or agreement.
Air Force: www.e-publishing.af.mil/shared/media/epubs/AFI36-2906.pdf
Marine Corps: http://www.lejeune.usmc.mil/legal/dependent_support_regulations.pdf
Coast Guard: http://www.uscg.mil/lsc/coast_guard_provisions.asp