((a)) The Secretary of the Navy and, by direction of the Secretary, the Chief of Naval Research and the chiefs of bureaus may, without advertising, make contracts or amendments or modifications of contracts for services and materials necessary to conduct research and to make or secure reports, tests, models, or apparatus. A contractor supplying such services or materials need not be required to furnish a bond.
((b)) This section does not authorize the use of the cost-plus-a-percentage-of-cost system of contracting.