Popular Mechanics (South Africa)
Gateway to the heavens
Deep Space concepts hint at how we’ll work, manufacture – and travel to Mars
Deep space concepts that will take us to Mars
TRANSPORT CONCEPTS unveiled by Boeing suggest an early 2020’s launch for a Deep Space Gateway project that could act as a portal for Mars Missions. The concepts, which both leverage proven solar electric propulsion technology and hardware, are intended to help achieve NASA’S goal of having robust human space exploration from the Moon to Mars.
NASA’S Space Launch System (SLS), which Boeing is helping develop, would deliver the habitat to cislunar space (between Earth and the Moon). Known as the Deep Space Gateway, the habitat could support critical research and help open opportunities for global government or commercial partnerships in deep space, including lunar missions.
“The ability to simultaneously launch humans and cargo on SLS would allow us to assemble the gateway in four launches in the early 2020s,” says Pete Mcgrath, director of global sales and marketing for Boeing’s space exploration division.
The Deep Space Gateway could be the waypoint for Mars missions. Utilising a docking system akin to what the International Space Station uses for commercial operations, it could host the Deep Space Transport vehicle, which would take humans to Mars. Once near Mars, crews could deploy a lander for surface missions or conduct other scientific and robotic missions in orbit. The transport vehicle would be
equipped with a habitat specifically designed to protect passengers from deep space’s harsh environment.
The gateway and transport systems are partially being developed as part of NASA’S Next Space Technologies for Exploration Technologies (Next STEP) public-private partnership programme.
CRUCIAL TO THE WHOLE ENDEAVOUR IS COST-EFFECTIVENESS. The problem is, once placed into orbit and separated from their launch vehicle, spacecraft must rely on their on-board propulsion systems for any further manoeuvring. On deep-space missions, propellant for on-board propulsion systems may make up more than half of the overall spacecraft mass.
That’s where Solar Electric Propulsion (SEP) comes in. Energised by the electric power from on-board solar arrays to ionise and accelerate xenon gas, the system will use 10 times less propellant than a comparable, conventional chemical propulsion system. This will slash spacecraft size and mission costs.
NASA’S Glenn Research Centre, which leads the Solar Electric Propulsion project for the agency, is preparing a system-level flight demonstration to launch later this decade. Technologies the project is developing and demonstrating include advanced solar arrays, high-voltage power management and distribution, power processing units and high-power Hall thrusters.
The SEP technology is nothing new, though; NASA has been refining it for more than five decades. The first successful ion electric propulsion thruster was developed at Glenn in the 1950s and the first operational test of an electric propulsion system in space was Glenn’s Space Electric Rocket Test 1 on 20 July 1964. Since then, NASA has increasingly relied on solar electric propulsion for long-duration, deep-space robotic science and exploration missions to multiple destinations, the most recent being NASA’S Dawn mission. The Dawn mission surveyed the giant asteroid Vesta and the protoplanet, Ceres, between 2011 and 2015.
HIGH-POWER SEP SYSTEMS UNDER DEVELOPMENT use electrostatic Hall thrusters instead of chemical rocket engines. The thruster traps electrons in a magnetic field and uses them to ionise the on-board propellant – in this case, the inert gas xenon – into an exhaust plume of plasma that accelerates the spacecraft forward. Several Hall thrusters can be combined to increase power and such a system can be used to accelerate xenon ions to more than 100 000 km/h. This will provide enough force over a period of time to move cargo and perform orbital transfers. In 2015, researchers successfully tested a new 12,5-kilowatt Hall thruster that employs magnetic shielding, enabling it to operate continuously for years; a capacity important to deep-space exploration missions.
To solve the problem of powering these systems, early development work in SEP involved large, flexible, radiation-resistant solar arrays that can be stowed into small, lightweight, more cost-effective packages for launch. After launch, these unfurl to capture solar energy and a pair of these large-scale arrays can provide approximately 50 kilowatts of electrical power. The SEP project worked with ATK Aerospace and Deployable Space Systems to build and test two solar array designs: one that folds out like a fan (ATK Megaflex) and another that rolls out like a window shade (DSS MEGA-ROSA). Both use lightweight structures and flexible blanket technology and are durable enough to operate for long periods in Earth orbit or passing through the punishing space environment, including the Van Allen radiation belts.
Aerojet Rocketdyne has been contracted to develop an advanced electric propulsion system that will significantly advance commercial space capabilities and enable deep space exploration missions. It’s expected that, besides the gain in fuel efficiency, the new system will provide more than double thrust capability of existing equivalents.
In the near future, the Asteroid Redirect Robotic Mission (ARRM), is intended to showcase the advanced system. The mission: to capture an asteroid boulder and place it in orbit around the Moon. ARRM will use a robotic spacecraft equipped with a high-power SEP system to visit a large near-earth asteroid, collect a multiton boulder from its surface, and conduct an asteroid deflection demonstration. The spacecraft will then redirect the multiton boulder into a stable orbit around the Moon, where astronauts will explore it and return with samples in the mid-2020s. – Source: NASA PM