Technical Issues and Solutions
One of the major limitations preventing humans from venturing farther into the solar system is the length of travel in space. And this, in turn, is directly related to the performance of the existing propulsion systems. It also places major limitations on the mass of payload that can be carried by rocket into space
Propulsion technologies can be grouped into three categories: "escape propulsion" (from Earth to orbit), "in-space propulsion" (in orbit), and "deep space propulsion" (from orbit to outer space). The launch vehicles currently used for "escape propulsion" rely on very mature technologies; however, there are prospects of significant technological advances for "in-space" and "deep space" vehicles, too.
Until now, propulsion used to operate the "escape propulsion" region in launch vehicles included variations of chemical propulsion. Satellite launch vehicles or spacecrafts operating "in-space" mainly rely on chemical propulsion (i.e. in-space propulsion); however, other propulsion types are also being increasingly researched and used now. The types of propulsion used to operate the "deep-space propulsion" region represent variations of chemical (i.e. escape and in-space) and non-chemical, (i.e. in-space and advanced) propulsion.
Improving and developing propulsion systems is key for future space exploration. As available data demonstrate, propulsion system malfunctions account for 58% of all launch failures. What this demonstrates is that a seemingly mature technology like this will require further improvements to become safer and more reliable. The scientific community’s interest in the field also confirms the need to develop more advanced propulsion systems.
Propulsion Systems: Propulsion Technologies
Propulsion Systems: Leaders and Innovators
Santa Clara, California, US, 2017
Momentus is developing an innovative water-based propulsion system for moving satellites and cargo in space. The system will enable companies to launch satellites into low orbit and “navigate” them to their precise position.
Boston, Massachusetts, US, 2014
Being one of the fourteen US companies selected by NASA for its Tipping Point partnership in 2019, Accion Systems specializes in developing technologies for Moon and Mars exploration. Accion will work with NASA’s Jet Propulsion Laboratory (JPL) to replace the cold gas propulsion system used for interplanetary CubeSats with a more efficient ion electrospray propulsion system.
Paris, Ile-de-France, France, 2017
ThrustMe, a French startup, has recently demonstrated its electric space propulsion system that uses iodine as a propellant. Iodine’s low price point solves the problem of unnecessary expenditure in creating a propulsion system for bigger satellites. That is precisely why ThrustMe’s technology is applied in next-generation satellites, as well as in products designed to solve problems associated with the increasing number of satellite constellations.
Christchurch, Canterbury, New Zealand, 2017
Dawn Aerospace builds same-day reusable launch vehicles and high-performance, non-toxic propulsion systems for satellites of all sizes. For their product SmallSat, the startup simplifies systems and replaces poisonous hydrazine with nitrous oxide and propene. For CubeSats, it increases capabilities by supplying 1.000x higher performance than electric-based propulsion systems with the same propellants.
Falls Church, Virginia, US, 1939
Northrop Grumman is a global security company providing solutions for sectors such as aerospace, electronics and technical services. Northrop Grumman is providing the five segment boosters for NASA's Space Launch System (SLS) and the main launch-abort motor and the attitude control motor for the Orion Crew Vehicle’s Launch Abort System (LAS).
Propulsion Systems: Propulsion Technologies
Space Propulsion researches and develops new technologies for more advanced in-space propulsion.
Navigation in Space
Being a collection of antenna arrays in California, Australia, and Spain, the Deep Space Network is the only tool for navigation in space. Everything from student-project satellites to the New Horizons probe meandering through the Kuiper Belt depends on it to stay oriented. An ultra precise atomic clock on Earth times how long it takes for a signal to get from the network to a spacecraft and back, and navigators use that to determine the craft’s position.
As more and more missions are sent into space, the network gets increasingly congested, causing the switchboard to be frequently busy. To address the problem, NASA is currently working on installing atomic clocks in spacecraft. They will enable to cut transmission time in half, allowing distance calculations with a single downlink. NASA is also developing higher-bandwidth lasers capable of transmitting big data packages, such as photos or video messages, much faster.
For future missions, Joseph Guinn, a deep-space navigation expert, wants to design an autonomous system that would collect images of targets and nearby objects and use their relative location to triangulate a spaceship’s coordinates without requiring any ground control. “It’ll be like GPS on Earth,” Guinn says.
Navigation in Space
Besides the difficulty of signal transferring, space navigation covers the following problems:
Deep space missions have a limited amount of power available for radio communication to and from Earth. Being a substantial distance from the Sun, they cannot generate enough energy all the time. The radio signals they transmit are very weak and have to be picked out of background noise. Furthermore, they take hours to reach the Earth.
Distances between destinations are significant, and the targets are too small and moving. If Earth were the size of a softball, the International Space Station would be orbiting just above the seams, the Moon would be a marble about 2 meters away, and Mars would be 1.2 to 2.4 kilometers away.
Navigators have to keep in mind that everything is moving and take into account not only speed of the spacecraft, but also the destination planet or moon.
The Sun's gravity determines the basic trajectory of an interplanetary spacecraft. But for deep space missions, a navigator also has to take into account gravitational forces from planets and moons and other forces that might affect the trajectory.
A computer-generated representation of all Cassini's Saturn orbits. The time frame spans Saturn Orbit Insertion on July 1, 2014 to the end of mission on Sept. 15, 2015.
Low Cost Space Technologies (SWOT Analysis)
This democratization and marketization of space are evident in the growth of the cubesat market. Small mass satellites are available at prices so low that it has attracted a growing number of customers (from Space Agencies to institutions like universities and schools), which in turn have enabled the creation of start-ups and spinoffs. This has led to the development of deployable structures to package relevant elements into small (cubesat compatible) volumes and then deploy them in space to achieve the required level of performance. Sometimes these act as demonstrations for applications aimed at larger satellites, like drag sails.
There are other technical issues that affect all smaller mass satellites, not just cubesats, and present significant challenges, like the need to achieve high platform stability. This is crucial for all missions supporting highly accurately targeted optical payloads (e.g., high-resolution cameras/telescopes or laser communication systems).