Specialized Networks for Space Flight

The history of Transmission Control Protocol begins in 1973, when Dr. Cerf Vint co-wrote a pioneering white paper on TCP/IP, the technology that gave birth to modern Internet communication. The Internet took almost twenty years to launch, and Cerf is now developing future communication requirements. He is currently working on a project to extend the Internet into space. The concept is not novel. Countries began exploring space fifty years ago to learn about the solar system (Conference on Smart Spaces et al., 2010). It became essential to communicate with these spacecraft by use of bi-directional radio connection to send directives, and for the probe to send information back to earth. The latter was achieved by use of the major gateways of Earth antennas, like the Deep Space Network (DSN) made by the National Aeronautics and Space Administration (NASA). At first, every mission used various protocols but as many mission were launched; all shared similar ground infrastructure, and thus, people started standardizing the model in which exchange of information was done.

The concept of Internet in space by use of current TCP/IP is an extension of this normalization. The DSN uses three research amenities placed strategically around the sphere to observe the spacecraft regularly as the Earth rotates. NASA is under the control and management of Jet Propulsion Laboratory (Frate, 2017). In the JPL, the Inter Planetary Network (IPN) runs the program. Tied in with this is the Mars Network that is researched at JPL as NASA’s potential future element for Mars Surveyor Program. The Mars planet is the closest to us in terms of environment and distance. The Mars Surveyor Program is meant to support ultimate human exploration, robotic outposts, surface exploration, global Mars reconnaissance, and sample return missions. However, to enable this, the Mars Network must develop a communications system, which will offer an increase in connectivity and data rates between Earth and Mars (Frate, 2017). Besides, it provides development of Mars’ navigational system, which will permit a more precise locational info while approaching Mars, mainly constructing a publicly reachable gateway on Mars (Conference on Smart Spaces et al., 2010). The first IPN step is to use the projected Mars portal and link it to Earth. To ensure this, there are several challenges to overcome that we will address later. The present Transmission Communication Protocol (TCP/IP) can be used on whichever planet for the local Internet but not in Specialized Space Travel Networks. As soon as the problems are addressed, and the astronauts can email back home, and it will be time to connect the other galaxy bodies to the network, but currently, it is still a challenge for NASA.

Research Questions

What is the most efficient way to communicate with the astronauts as they travel into deep space?

Are the “plain old TCP/IP” and the World Wide Web sufficient to take humanity safely into deep space?

Are the current networks, protocols, and standards good enough?

Do new standards need to change and evolve to meet the requirements for effective space communication?

Research Methodology

The study employed a qualitative research design approaches targeting both secondary and primary sources. Computerized data bases were searched, and internet resources such as web searches for NASA and Space X press releases, as well as the Hunt’s Library was used to complete this project.

Literature Review

Present Status

According to Frate (2017), the JPL has implemented a conceptual study of the planned Mars Network, focusing on Microsat, a detailed project of a small prototype satellite. The Mars Network would comprise of several communication Microsats around Mars, and at least one larger, more proficient MARSat satellite that is acting as a greater bandwidth gateway to Earth (Frate, 2017). The overall IPN plan is to create remote Internets somewhere else in the Solar System connected with an Interplanetary Backbone Network (IBN). The remote Internets can use protocols analogous to Earth's Internet, while the IBN necessitates a new significant development effort. Most of the work done in constructing Earth’s wireless networks will be appropriate to remote Internets, where ground-based networks are impossible (Frate, 2017). The IPN will simplify the future communications component of space exploration missions but not with the current TCP/IP architecture (Frate, 2017). Presently, every mission needs to incorporate its own personalized communications infrastructure. In some years to come, missions will solely use the IPN, which is the most fundamental requirement for specialized space travel networks. Besides, the JPL has scrutinized when, how, and in what configuration and order of launching such satellites to have a Mars Network up and running as soon as possible.

Lastly, the JPL has discovered the construction of a Mars Exploration Gateway to link the Mars Internet and Network. In cooperation with academia and the industry, NASA has plans for making this gateway accessible to the public (Frate, 2017). Public participation in space exploration missions of the future would strengthen NASA’s government funding and increase its public profile. Nonetheless, this capability will request security of the highest order. A working prototype known as CCSDS File Delivery Protocol (CFDP) has been developed, and its experimental implementations exist. It is tremendously limited in scope and was aimed at supporting individual space exploration missions; however, it served as a basis for further work. The IPN Research Group, led by Dr. Vint Cerf, has printed an Architectural Definition of a possible IPN protocol as a functioning document of the Internet Engineering Task Force (IETF). It recommends a store and forward network overlay above the transport layers of the underlying IPN networks (Frate, 2017). The protocol is anticipated to operate in locations, which have intermittently connected networks and very long speed of light delays.

The Space Communications and Navigation (SCaN) facility at the Headquarters of NASA leads the Delay Tolerant Networking (DTN) research with the aim of advancing the heritage and maturity (space flight use) of the communication protocols of DTN (Frate, 2017). Delay tolerant networks use the store and forward methods within the network to compensate for intermittent link connectivity. The fundamental concept of DTN is an architecture based on Internet-independent middleware whereby protocols at all layers, which best suit the operation are used in each environment, with a new bundle protocol (overlap network protocol) implanted between the locally optimized communications stacks and the applications (Jenkins et al., 2010). Several applications can benefit from the delivery of the messages in the loose network.

Problems Associated with Current TCP/IP protocols

The study by Harras (2008) proofs that the rise in the number of Mars Networks and Mars exploration elements brings with it an upsurge in the difficulties involved in trying to synchronize the communications using TCP/IP and the Worldwide Web. To solve this problematic, Mars Network, a probable future element of NASA’s Mars Surveyor Program studied at JPL is working with the Internet community in designing a Mars Internet (Harras, 2008). They try to do this by using TCP/IP protocol, which facilitates file-level communications between constellation elements and exploration. However, the TCP/IP protocol is not robust enough to contend with the noisy, intermittent, power-constrained and the long, round-trip light-times deep space links.

According to the research by Haras (2008), the “plain old TCP/IP” and the World Wide Web are not sufficient to take humanity safely into deep space for now as communications between Earth and spacecraft are intolerable. Data transmission between Earth and space is thru antenna clusters on three landmasses, located nearly 120 degrees apart around the world (Haras, 2008).The arising communication problems are due to inadequate bandwidth. With more than forty active missions a month vying for time on the network, the system is increasingly becoming overloaded. He claims that new TCP/IP architecture is required to change and evolve to meet the requirements for efficient space communication.

Haras (2008) further argues that robotic probes deployed by NASA should make sure that strong links of communication exist between themselves and Earth. Such reliable links cannot be attained using the current TCP/IP protocols as communications performance declines as the square distance increases. A satellite conveying 400 million km from Mars to Earth would make connections 100 million times more problematic (Haras, 2008). This astral distance between planets also leads to long delays between subsystems or parties, for instance, a round-trip transmission to Mars from Earth can exceed 40 minutes.

According to Jenkins et al., (2010), security is also a concern. Currently, Internet security protocols (TCP/IP) necessitate a sequence of 'handshakes' to certify permission and correct identity. This tactic will not work for the IPN since real-time communication is unpractical. As a result, we need to incorporate Secure Sockets Layer (SSL) and other protocols presently used for e-mail security (Jenkins et al., 2010). Antennas must know when and where something will be to be ready to receive or send a signal. Besides, they need to take into account the fact that transit time’s changes and the celestial mechanics also orbit the sun. There is also the frustrating fact that when two sources find themselves on opposite sides of the solar system, the sun can block signals for weeks.

According to Sinise et al., (2008), in contrast, the internet is a linked network where internet protocols, particularly transmission control protocol/internet protocol (TCP/IP), are reliant on low latencies of about milliseconds. This low latency, coupled with high bit error rates (BER), permits TCP to unreliably receive and transmit acknowledgments for messages navigating the terrestrial Internet (Sinise et al., 2008). High BER links, one of the best examples of high latency, with intermittent connectivity is that of space communications. A one-way trip space-time, at the speed of light, from the moon to the Earth incur a 1.7 seconds delay; whereas one-way trip times to Mars incur a minimum of eight minutes delay. The latency problem for interplanetary links is exasperated with greater BER due to solar radiation. Besides, the celestial bodies are in continuous motion, which can block the obligatory line of sight between receive and transmit antennas, resulting in intermittently connected links only (Sinise et al., 2008). Additionally, broken connectivity links are commonplace terrestrially. For instance, the plethora of battery-powered mobile communications devices, which go in and out of communication range to interface wired service points and are turned off and on at the users’ discretion.

Findings and Discussions

From the literature insights above, the current TCP/IP is not robust to resist disconnections, disruptions, and delays in space. Glitches can occur when long communication delays and solar storms occur, or when a spacecraft travels behind a planet. The delay in receiving or sending data from Mars takes about three-and-a-half to twenty minutes at the speed of light. Modern TCP protocols are well known in offering reduced deep space networks performance, which is characterized, by the asymmetrical blackouts and bandwidth, link errors, and tremendously high propagation delays (Haras, 2008). The window-based congestion regulator that inserts a new packet into the network upon an ACK reception is liable for such degrading performance because of high propagation delay. Slow start TCP protocols algorithms further contribute to the degrading performance by wasting long time intervals to reach the exact data rate. Furthermore, wireless link errors magnify the problem by misleading the TCP source to throttle the overcrowding window unnecessarily. The salvage from erroneous window decline takes a definite time that is proportional to the RTT (round-trip time) and further decreases the performance of the network. Another problem is that the current TCP/IP assumes a continuous end-to-end connection (Frate, 2017). In its design, the data packets are discarded if a destination path is not found. Not all network nodes keep the info, as it is required until it can safely communicate with another node. This non-store-forward method implies that information is lost when no right destination path exists. Eventually, the info is not conveyed to the end user.

The other challenging issue is that the planets and their satellites are in motion, and the majority are rotating. The rotation of the planets implies that if you are speaking to something that is on the planet’s surface, it may turn out of the line of sight so you cannot speak to it any longer until the device on the surface revolves into sight again. The same might be said about some revolving satellites. You have to develop protocols, which will deal with the fact that you cannot consistently converse with the other party: the communication is potentially disrupted and delayed (Frate, 2017). More problems must be addressed by the new deep space networks transport protocols. These problems are consequences of the features of the most profound space-connections, and can be summed as follows:

• Delayed Feedback: TCP is expected to respond to network state, i.e., TCP should deal with the network state changes. This expectation creates problems in great delay surroundings, as TCP uses end to end signaling for its control loops. As the higher RTT is experienced, the older information concerning link conditions is received at the source (Haras, 2008). Hence, the decision of the congestion control schemes based on such past info may not lead to appropriate action. Consequently, congestion control systems that are developed to act to prompt congestion situations do not produce suitable links’ response by a large propagation delay.

• Buffer Size: In order to guarantee 100% reliable transport, retransmission mechanism is unavoidable. Nonetheless, this brings a substantial amount of memory requirement (Haras, 2008). For instance, the transport protocol source must maintain 1.2 GB buffer size for RTT of twenty minutes and the transmission data rate of one MB/s.

Concluding Remarks

As NASA prolongs its reach to the Moon and beyond, a networked architecture, DTN will be necessary apart from “plain old TCP/IP” to complete these missions successfully. The experiments, which will be done, are designed to test the DTN protocol suite in a real space environment and to determine how the TCP/IP protocols perform and what enhancements may be required to be made. The effect of the research outcomes will help in advancing the technical maturity of the DTN communications technology so that it is accessible for NASA use in both robotic and human Exploration missions. Therefore, as for now, it is evident from the literature above that the current TCP/IP does not have the necessary architecture to facilitate specialized Networks for Space Travel, take humanity safely into deep space, and effective communication with astronauts.

References

Conference on Smart Spaces, Balandin, S. I., Dunaytsev, R., Koucheryavy, Y., & NEW2AN (Conference). (2010). Smart spaces and next generation wired/wireless networking: Third Conference on Smart Spaces, ruSMART 2010 and 10th international conference, NEW2AN 2010, St. Petersburg, Russia, August 23-25, 2010 : proceedings. Berlin: Springer.

Harras, K. A. (2008). Challenged networks: Protocol (TCP/IP) and architectural challenges in delay and disruption tolerant networks. Saarbrücken, Germany: VDM Verlag Dr. Müller.

Jenkins A, Kuzminsky S, Gifford K, Pitts RL, Nichols K. (March 13, 2010). Delay/Disruption-Tolerant Networking: Flight test results from the international space station. 2010 IEEE Aerospace Conference, Big Sky, MT; 2010 March 6-13

Frate, A. D. (May 26, 2017). NASA Networks. Science & Technology Libraries, 8, 2, 57-61.

Sinise, G., Goodchild, T., Botting, K., Fields, E., Crisp, M., Green, N., Dale, R., Image Entertainment (Firm). (2008). when we left Earth: The NASA missions. Silver Spring, MD: Discovery Communications.