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Blockstream Satellite Review, StarLink & Adam Back
January 23  |  5 min read

The Blockstream Satellite Team Reveals Details In Their Reddit AmA

COIN360 Editorial Team

Blockstream Satellite is an innovative project that broadcasts the Bitcoin blockchain to the entire planet via satellite, no internet connection required. On January 16th, Adam Back, Chris Cook and rest of the team behind the project hosted an AmA (Ask me Anything thread) on Reddit. This took place just after the Blockstream Satellite service completed coverage for the Asia Pacific Region (adding to the already-existing coverage of North & South America, Europe and Africa) and the announcement of their Satellite API , which can be used to beam down private messages from in-orbit satellites.

Who is Adam Back?

One could easily say Adam Back deserves more recognition than he gets. His endeavors in cryptography can be dated back to 1997 with the development of Hashcash, an anti-spam system that paved the way for today’s PoW system. This eventually inspired Satoshi Nakamoto, who mentions Back as a source for the Bitcoin white paper.

Why should Blockstream Satellite be used?

BlockStream Satellite bypasses potential external restrictions while also saving costs and providing a more stable network. Thanks to the sheer amount of satellites orbiting in space, it is “nearly impossible” to know if a certain satellite is receiving Bitcoin data or just broadcasting TV shows. The satellite service is uni-directional (receive-only) so it works just like car radios do. Both of these facts bolster the privacy of the service – it is not even possible to check how many people are using it at any given point in time.

Several benefits of transferring Bitcoin through a satellite were mentioned. One of the most prevalent use-cases for the service is for people who struggle to keep a node synced due to bad connection in rural areas, bad ISPs or governmental bans, or filters for BTC data.

The company also revealed specific information of the satellites themselves. Instead of launching satellites on their own, they are leasing a small part of the bandwidth from 4 commercial geo-stationary satellites: GALAXY 18, EUTELSAT 113, TELSTAR 11N and TELSTAR 18V. The last one was launched as recently as September 2018, and it provides high-throughput communications coverage to China, Mongolia, Southeast Asia, and the Pacific Ocean region. Their plan is to eventually purchase their own satellites, but since leasing bandwidth from other satellites is significantly cheaper, it remains as a goal for the far future.

The Blockchain Satellite API Beta was launched during the AmA. During the beta stage, people can pay with testnet Lightning BTC, which means that broadcasts are momentarily free.


Answering questions about the performance of the service, the team stated that Blockstream Satellite has been continuously operational since the August 2017 launch, with the exception of a short interruption during a hurricane in 2018, which disrupted an uplink. In that event, the stream down-time self-recovered, thanks to its 24-hour data retransmit feature, which is activated in the case of service interruptions or power cuts and outages. This feature rebroadcasts the last 144 blocks in a rollin 24-hour window.

They are interested in improving their service as demands grows, which could potentially even include retransmitting full block data, although that would mean hundreds of gigabytes per day.

Satellite bandwidth is currently 96kbps, but only 86kbps are dedicated to blocks, the remaining 10kbps allocated to sending API data. However, they stated that future upgrades will bring dynamic bandwidth allocation. As things stand though, the amount of bandwidth was described as “relatively modest”, since it’s less than a TV channel.

A user also asked about the possibility of broadcasting Lightning transactions on the satellite network. To this, Adam brought up the uni-directionality of the satellite service (receive-only) as being incompatible with the interactive protocol of the Lightning network. However, he also outlined a way to circumvent this: run a fullnode using the satelite, use that fullnode to run a lightning node, and use a more expensive per MB or slower internet connection to establish lightning connection and be able to send and receive lightning transactions.

User friendly solutions

When asked about possible “plug and play” hardware solutions that could simplify setting up a satellite fullnode, the team linked to a flat pannel antenna and referred to other kits that are in the works that could streamline the experience of setting up the dish. Another option they approved was the use of an old Directv dish, although they recommend using a 60 cm one. You can check a collection of Blockstream satellite setups here.

Is it free?

Regarding their business model and potential cost of the service, the team stated that there will be incremental per-transaction or message fees. They said that transactions are usually within the 250 bytes range and that the minimum message size is one kilobyte. Additionally, the minimum bid per byte is set at 50 milisatoshis, meaning that a minimum priority message could be set for 50 satoshis ($0.0017715258). This is also not the only revenue source for Blockstream, who also offer a wide range of products on their website, such as GreenAddress Wallet, ICE/Blockstream crypto data feed and a paid service API for satellite data.

StarLink and other projects

When enquired about the possible threat that projects such as Elon Musk's StarLink (which involves 12,000 satellites) pose for BlockStream Satellite, they said that they look at it as a platform for exciting possibilities rather than a threat that will make them obsolete. The one-to-many nature of satellite broadcasts allows for scaling issues to be tackled without any additional operational overhead. However, bi-directional satellite services are tracked per user and only available for subscribers, which goes directly against the privacy aspect Blockstream Satellite.

Worldwide last mile connectivity

In relation to the future applicability of mesh networks and LoRa technology, the team responded that the point of Bitcoin satellite also aims to be the backbone for last mile connectivity around the world and get more people to engage directly in the Bitcoin network. Adam refers to meeting individuals and entrepreneurs in local communities to talk about their projects, such as the Locha team, who is working to provide mesh and LoRa technology in Latin America.

Mixed reception

While most of the people who took part of the AmA were thankful for the service, some users also raised some concerns. One of them mentioned that thanks to the last FIBRE update it was possible for different satellites to send different signals, something that would be very beneficial for users that can see more than one satellite since it halves the block reception delay and doubles the robustness to packet loss. However, Blockstream is still sending the same signal on all satellites. Other concerns raised by the same user are related to data encoding, which could be 25-30% more efficient if they adopted the new changes in data encoding; the FIBRE implementation, which still needs some work regarding packet loss and design tradeoffs; the blocksat modem, whose efficiency could be vastly improved on fast computers, yet there are still problems with getting a very low packet loss rate; the demanding system requirements for decoding, which alienates a big portion of its potential user-base; and the already mentioned problems related to the fixed allocation of bandwidth dedicated to API and bitcoin data.

The user notes that some of these problems, such as the ones with the blocksat modem, are complicated a highly technical; where others, like the bandwidth allocation issues and the possibility of different satellites sending different signals, are problems that can be fixed more easily in future updates.

Another user, however, criticized Blockstream for their (allegedly) disingenuous description of the service as decentralized, when it’s actually a centralized data service with a centralized satellite provider. Adam Back responded stating that users shouldn’t trust the uplink Bitcoin fullnode operated by Blockstream, but rather **verify** the transactions. The fact that any user can verify the transactions is what makes it secure.

Coin360 Editorial Team