DARPA hunts hypersonic airplane-like spacecraft that can go Mach 10

Source: Network World
The idea is cool enough – build a reusable aircraft-like system that could easily and relatively cheaply launch satellites into orbit.
The kinks will be that the system need do that for somewhere in the $5 million per launch range and oh yeah, go well over Mach 10.
As you might have guessed, the project to develop such a system is being put forth by Defense Advanced Research Projects Agency (DARPA) which will more fully detail the program, known as the Experimental Spaceplane (XS-1) in October.
From DARPA: “The objective of the XS-1 program is to design, build, and demonstrate a reusable Mach 10 aircraft capable of carrying and deploying an upper stage that inserts 3,000- 5,000 lb. payloads into low earth orbit (LEO) at a target cost of less than $5M per launch. The XS-1 program 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.”
DARPA said that the long-term intent is for XS-1 technologies to be transitioned to support not only next-generation launch for government and commercial customers, but also global reach hypersonic and space access aircraft.
The lofty technical challenges that will be part of the XS-1 program include:

• A reusable first stage vehicle designed for aircraft-like operations
• Robust airframe composition leveraging state-of-the-art materials,

manufacturing processes, and analysis capabilities

• Durable, low-maintenance thermal protection systems that provide protection

from temperatures and heating rates ranging from orbital vacuum to
atmospheric re-entry and hypersonic flight

• Reusable, long-life, high thrust-to-weight, and affordable propulsion systems
• Streamlined “clean pad” operations dramatically reducing infrastructure and

manpower requirements while enabling flight from a wide range of locations
For the first round of testing the XS-1, DARPA says it wants to see the spacecraft”

• Fly ten times in ten days
• Fly to Mach 10 at least once
• Launch a representative payload to orbit at least once

“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.”
Commercial, civilian and military satellites provide crucial real-time information essential to providing 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. Moreover, U.S. 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 is increasingly critical for U.S. Defense Department operations. In the end the idea is to lower satellite launch costs by developing a reusable hypersonic unmanned vehicle with costs, operation and reliability similar to traditional aircraft, Sponable stated.
[RELATED: NASA wants more hypersonic spaceship research]
The agency noted that it already has one quick, cheap satellite launch program working . The Airborne Launch Assist Space Access (ALASA) program looks to develop an aircraft-based satellite launch platform for 100 lbs. payloads and building low-cost, small satellites that could be rapidly be launched into any required orbit, a capability not possible today from fixed ground launch sites, DARPA stated. Boeing, Lockheed Martin and Virgin Galactic are working on separate offerings for that project.
DARPA also has the Integrated Hypersonics program aimed at researching and developing what it calls “next- generation technologies needed for global-range, maneuverable, hypersonic flight at Mach 20 and above for missions ranging from space access to survivable, time-critical transport to conventional prompt global strike. The program seeks technological advances in the areas of: next generation aero-configurations; thermal protection systems (and hot structures; precision guidance, navigation, and control; enhanced range and data collection methods; and advanced propulsion concepts.”
DARPA has in the past equated the development of hypersonic equipment to the development of stealth technology in the 1970s and 1980s. The strategic advantage once provided by stealth technology is threatened as other nations’ abilities in stealth and counter-stealth improve. “Restoring that battle space advantage requires advanced speed, reach and range. Hypersonic technologies have the potential to provide the dominance once afforded by stealth to support a range of varied future national security missions,” DARPA said.
There are a ton of technological issues to be addressed, one of the biggest being the heat generated by extreme speeds.
At Mach 20, vehicles flying inside the atmosphere experience intense heat, exceeding 3,500 degrees Fahrenheit, which is hotter than a blast furnace capable of melting steel, as well as extreme pressure on the shell of the aircraft, DARPA stated. The thermal protection materials and hot structures technology area aims to advance understanding of high-temperature material characteristics to withstand both high thermal and structural loads. Another goal is to build structural designs and manufacturing processes to enable faster production of high-speed aeroshells, DARPA stated.