Experimental Spaceplane (XS-1)

Commercial, civilian and military satellites provide crucial real-time support to strategic national security advantages to the United States. The current generation of satellite launch vehicles, however, is expensive to operate, often costing hundreds of millions of dollars per flight. ). For example, the U.S. Air Force's Evolved Expendable Launch Vehicle (EELV) and Minotaur IV launch vehicles have dramatically increased in cost since the inception of the programs. Moreover, US launch vehicles fly only a few times each year and normally require scheduling years in advance, making it extremely difficult to deploy satellites without lengthy pre-planning. Quick, affordable and routine access to space has long been an objective for U.S. Defense Department operations.

DARPA established the Experimental Spaceplane (XS-1) program to develop a fully reusable unmanned vehicle that would provide aircraft-like access to space. The vehicle is envisioned to operate from a “clean pad” with a small ground crew and no need for expensive specialized infrastructure. This setup would enable routine daily operations and flights from a wide range of locations. XS-1 seeks to deploy small satellites faster and more affordably, while demonstrating technology for next-generation space and hypersonic flight for both government and commercial users.

“We want to build off of proven technologies to create a reliable, cost-effective space delivery system with one-day turnaround,” said Jess Sponable, DARPA program manager heading XS-1. “How it’s configured, how it gets up and how it gets back are pretty much all on the table—we’re looking for the most creative yet practical solutions possible. ... XS-1 aims to help break the cycle of launches happening farther and farther apart and costing more and more... It would also help further our progress toward practical hypersonic aircraft technologies and increase opportunities to test new satellite technologies as well.”

XS-1 envisions that a reusable first stage would fly to hypersonic speeds at a suborbital altitude. At that point, one or more expendable upper stages would separate and deploy a satellite into Low Earth Orbit. The reusable hypersonic aircraft would then return to earth, land and be prepared for the next flight. Modular components, durable thermal protection systems and automatic launch, flight, and recovery systems should significantly reduce logistical needs, enabling rapid turnaround between flights.

Key XS-1 technical goals include flying 10 times in 10 days, achieving speeds of Mach 10+ at least once and launching a representative payload to orbit. The program also seeks to reduce the cost of access to space for small (3,000- to 5,000-pound) payloads by at least a factor of 10, to less than $5 million per flight. The focus of the program is the overall system design, the reusable first stage vehicle, and the operations concepts that are integral to the spaceplane architecture. The challenge is developing an X-Plane program that satisfies the program goals within the cost constraints by using near-term and advanced technology and operations.

Successful demonstration of these goals will provide a proof-of-concept for responsive space launch capabilities. Flying ten times in ten days will demonstrate aircraft-like operability and requires a “clean pad” model along with rapid recovery and reconsitituion, thus creating a new paradigm for routine space operations. The ability to launch a payload to orbit at less than $5M will represent approximately a 10X cost reduction compared to Minotaur IV capabilities, with potential for further reductions using scaled-up systems. Flying to Mach 10 or greater will reduce both the size and cost of the expendable upper stage and result in aero-thermal environments enabling the acquisition of much-needed data for future hypersonic development. Delivering a launch capability for responsive payloads will provide an immediate operational benefit to military, civil, and commercial stakeholders. It should be noted that $5M per orbital launch is a target goal for an operational system. This includes direct launch costs (fuel, labor), expendable upper stage(s) (not including the payload), and amortized indirect costs, all assuming at least 10 flights per year.

XS-1 will directly address the need for small payloads launched using low cost and operationally efficient concepts of employment (CONEMPs) based on a "clean pad" approach. Moreover, it will provide a foundation to build upon for larger launch systems in the future. It is also envisioned that the XS-1 program will mature many of the key technologies and operational processes needed to enable future hypersonic aircraft and space access vehicles. Missions performed by such follow-on vehicles could include hypersonic technology maturation and routine global reach intelligence, surveillance and reconnaissance (ISR) as well as other military applications. The potential to transition XS-1 designs, technology and corresponding operating concepts to future aircraft is an important opportunity for the program.

Multiple awards are anticipated in Phase I, in two types: 1) system design tasks, and 2) critical risk reduction tasks. Each Phase I system design task performer may be initially awarded up to $3.0M, with an option for up to an additional $1.0M. Each Phase I critical risk reduction task award will be for up to $1.0M per performer. During the first phase, one or more proposals may be selected to 1) develop the XS-1 demonstration concept, 2) identify core component technologies, 3) conduct critical risk reduction, and 4) develop a technology maturation plan that allows flight demonstration and validation of system capabilities.

Phase I will be a 13-month effort focused on developing the XS-1 demonstration concept, identifying core component technologies, conducting critical risk reduction, and developing a technology maturation plan that allows flight demonstration and validation of system capabilities. During Phase I, system design performers will be required to hold a mid-phase Conceptual Design and System Requirements Review. Performers must also deliver a Technology Maturation Plan (TMP), address airworthiness and safety certification (Government and/or commercial), and identify candidate upper stage vehicles and representative payloads to demonstrate the XS-1 program goals.

Each Phase I system design task performer may be initially awarded up to $3.0M, with an option for up to an additional $1.0M. Proposers seeking to obtain the $1M of optional system design funding in Phase I must indicate what tasks would be performed with this funding, how these tasks would contribute additional depth and/or breadth to the baseline Phase I deliverables, and how these tasks would enhance the outcome of subsequent phases. If proposed and included in the Phase 1 award, the Government, at its sole discretion, will determine whether or not to exercise the option for a given performer.

The program will perform risk reduction and design, then, if approved to proceed to Phases II and III, fabricate and fly an experimental autonomous spaceplane. Toward the end of Phase I, the Government will determine whether to proceed to Phases II/III. If so, one system design performer will be selected to proceed into Phase II. Awards are subject to the availability of funds.

On 15 July 2014 DARPA awarded prime contracts for Phase 1 of XS-1 to three companies: The Boeing Company (working with Blue Origin, LLC) Masten Space Systems (working with XCOR Aerospace) Northrop Grumman Corporation (working with Virgin Galactic).

In order to achieve the objectives of the XS-1 program, performers were expected to conduct their program activities with capable, experienced, creative, and effective personnel teams. Lean management and systems engineering principles would be employed by DARPA and should be employed by performer teams. The goal is to empower personnel while minimizing management overhead associated with both Government and internal performer company processes. Performers’ personnel teams were expected to execute a flexible, adaptive, and streamlined program where decisions can be made expediently based on technical merit, programmatic merit, and up-to-date information without rigid and inflexible adherence to traditional top-down program management models.

XS-1 would complement a current DARPA program already researching satellite launch systems that aim to be faster, more convenient and more affordable: Airborne Launch Assist Space Access (ALASA). ALASA seeks to propel 100-pound satellites into orbit for less than $1 million per launch using low-cost, expendable upper stages launched from conventional aircraft.

An airworthiness assessment is “A technical evaluation of data against specific airworthiness criteria and determination of residual risk.” This so called “basis” is the criteria to approve a flight test program. The airworthiness certification is “an assurance by an airworthiness authority that all tenets of the airworthiness process are met to their standards and that the configuration of the aircraft or air system is safe for flight without significant hazard to aircrew, ground crew, passengers, or to other third parties.”

The XS-1 program is unique in that it is a rocket powered unmanned aerial vehicle or UAV that may be airdropped for flight testing from an aircraft. Therefore JSSG guidelines on UAVs and FAA Part 23, 25, 27, and 29 may apply for part of the program, and FAA Part 400 apply to actual rocket powered space launch. Regardless, the FAA and Air Force guidelines essentially collect the same data that you would use in a good system engineering process.