Delta-V

Europeans Constructing Reentry Test Vehicle

Suborbital flights will give ESA experience vital to its ambitions for a human spaceflight program.

Stephen Cass 07/24/2009

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This week the European Space Agency commissioned aerospace company Thales Alenia to build the unmanned European Experimental Reentry Testbed (EXPERT) vehicle. EXPERT will be launched by a Russian Volna rocket (basically a converted submarine-launched ballistic missile), reaching an altitude of 100 km, and reentering the atmosphere at 5 km per second.

Europe would like to develop its robotic cargo ship, the ATV, into something that could carry astronauts to and from the International Space Station. But while the ATV has demonstrated that Europe can orbit a pressurized vehicle successfully, the ATV has no ability to return to Earth, burning up in the atmosphere after its supply missions have been completed. An upgraded version of the ATV, known as the Advanced Rentry Vehicle (ARV), will demonstrate the ability to return a payload safely from orbit, but before it can be constructed, Europe needs to gain the kind of information about reentry behavior that the U.S. and Russian programs obtained decades ago during the earlier days of their manned space programs.

ESA hopes that EXPERT will start providing this data after it begins flying in 2010. EXPERT will also demonstrate a parachute system for soft landings--another vital technology if Europe wants its astronauts to come back in one piece.

Speeding Up Space Communications

The Interplanetary Internet makes its debut on the space station.

Brittany Sauser 07/09/2009

The first node of the Interplanetary Internet, a robust Internet-style communications network for outer space, has finally made its way to the International Space Station (ISS), and has already sent back its first set of data--images of crystals formed by metal salts in free-fall.

The system is a new communications protocol intended to speed up the delivery of data from spacecraft to earth. Robotic equipment has been flying to space since the 1960s, communicating with earth by using either point-to-point radio links or the Deep Space Network (DSN), built by NASA in 1964. While these communication schemes have been efficient, they're like using dial-up AOL to access the Web when better technology is available. And as the number and complexity of missions increases, it will only become more problematic. So ten years ago Vint Cerf, who designed the networking protocols that launched the Internet, joined a team at NASA's Jet Propulsion Laboratory and built the Interplanetary Internet.

The system is modeled after the terrestrial network, but instead of using its standards called the TCP/IP protocol suite--packet switching and store-and-forward methods--the Interplanetary Internet uses delay- and disruption-tolerant networking (DTN)--routing information through hosts that hold on to it until a communications link can be established. "The team set out to develop a suite of protocols that would allow us to have the kind of network flexibility in space that we have on Earth," said Cerf, also Google's vice president and chief internet evangelist, in this interview with me, in which he also discussed, in-depth, the technical details of the system.

The system was first tested for a month in November 2008--a spacecraft 20 million miles away from Earth sent dozens of images back. Now that the first node is permanently on ISS, I think astronauts and robotic spacecraft will finally have the opportunity to send more data with fewer constraints--communications won't be blocked when the ISS travels behind a planet or experiences power outages. And since the system holds onto information at one node until it finds the next node in the chain, energy won't be wasted by continually trying to communicate until everything is sent, such as the case with Earth Internet protocols. In addition, the new system could alleviate traffic to the DSN. Thus, we should get more information from space faster, enhancing our knowledge of what's out there. Also it provides an avenue for astronauts to communicate more frequently with the public.

A second Interplanetary Internet node will be sent to the station later this year.

Bio

This blog focuses on the nuts-and-bolts of space technology. We're interested in the hardware that's actually going into orbit and beyond. We write about what's involved in building, launching, and operating spacecraft, exploration vehicles, and habitats (and what it takes on the ground to support them) today.

Delta-V is written by Stephen Cass, a senior editor at TR who has covered space technology and exploration for nine years, and Brittany Sauser, a space technology reporter at TR.

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