If satisfied that the application is not for the purpose of discovery, and that its allowance may prevent future delay or failure of justice, and that the applicant is unable to bring the contemplated action or cause it to be brought, the court shall order the testimony perpetuated. In its order, the court shall designate the deponents, the subject matter of their examination, the time, location and officer before whom the depositions shall be taken, and whether orally or on written interrogatories.