SpaceX scrubs second launch for Space Development Agency's Tranche 0, but still on for Starlink mission

Sep 06, 2023

SpaceX has delayed the launch a batch of 13 communications and missile tracking satellites from Space Launch Complex 4 East (SLC-4E) at Vandenberg Space Force Base on the Tranche 0 Flight 2 mission for the Space Development Agency (SDA). An issue with engine 4 caused the scrub, with the next opportunity set for Friday. However, SpaceX will still attempt to launch its Starlink Group 6-13 mission later on Thursday.

The SDA mission will be SpaceX’s 50th launch from Vandenberg. After conducting a total of 19 launches from SLC-4E from 2013 through 2021, the pace has picked up recently with 13 missions in 2022 and 17 flights already completed in 2023.

Tranche 0, Flight 2

The Falcon 9 booster used for this mission, B1063-13, has previously launched Sentinel-6 Michael Freilich, DART, Transporter-7, Iridium OneWeb, and eight Starlink missions. After separating from the second stage the booster will return to Landing Zone 4 at Vandenberg Space Force Base. The Falcon 9 second stage will be deorbited south of South Africa a couple of hours after the launch.

The operational orbit for the satellites will be near 1,000 km in altitude with an inclination of 81 degrees.

The first Tranche 0 launch placed its payloads into an initial orbit of approximately 940 by 950 kilometers in altitude. Two of the satellites have since raised to an operational orbit closer to 960 by 980 kilometers.

This is the second of two launches for SDA’s Tranche 0, the demonstration phase of the new Proliferated Warfighter Space Architecture (PWSA), formerly known as the National Defense Space Architecture. SpaceX was awarded a 150 million dollar contract on Dec. 31, 2020, for two flights of Falcon 9.

Lockheed Martin Tranche 0 Transport Layer satellites. (Credit: Lockheed Martin)

The 13 payloads on this flight include 10 Transport Layer satellites from Lockheed Martin, one Transport Layer satellite from York Space Systems, and two Tracking Layer satellites from SpaceX.

The first flight in April carried eight Transport Layer satellites from York and two Tracking Layer satellites from SpaceX. One Transport Layer Type A satellite from York Space Systems will now be used as a testbed on the ground instead of launching, and four Tracking Layer satellites from L3Harris will share a launch with the Missile Defense Agency later this year.

The SDA was established in March 2019 to serve as a “constructive disrupter” for the Department of Defense (DOD) space acquisition. SDA’s focus is to perform spiral development of PWSA, a proliferated low-Earth Orbit constellation, that will provide communications, missile warning/tracking, and other functions to the DoD by deploying many smaller, less expensive, and faster to produce spacecraft than traditional DOD satellite systems. SDA became part of the Space Force on Oct. 1, 2022.

The SDA’s motto is “Semper Citius,” meaning always faster. The goal is to regularly field new batches of satellites that improve in capability over time, rather than design exquisite systems that would likely come in years late and over budget. Every two years the SDA will procure a new Tranche of satellites that can include multiple layers performing different functions.

Each tranche is openly competed so that new vendors have an opportunity to participate in the program. Building a constellation of interoperable satellites from multiple vendors is a key goal of the program. This has been a boon to several suppliers of small satellite buses and optical inter-satellite links (OISL) that have been able to begin producing higher volumes of its products. The constellation will eventually include hundreds of satellites in near-polar orbits at 1,000 kilometer altitude.

Transport Layer satellites are the backbone of the network, carrying RF and optical communication payloads, with the optical links forming a mesh network. There are tactical Link 16 payloads to communicate with forces in the field, as well as other RF payloads to communicate with ground stations. For Tranche 0, there are two types of Transport satellites: Group A (13 satellites) has two OISL as well as RF communications, while Group B (seven satellites) has two OISL and Link 16 tactical data links. In Tranche 1 the Transport satellites will have more OISL and tactical data links on each spacecraft. This second launch has seven Group A and four Group B Transport satellites.

Tracking Layer satellites serve an overhead persistent infrared imaging function for missile warning and tracking with a wide field of view payload, and can communicate with the Transport Layer satellites over optical links. They are designed to track advanced missiles including hypersonic glide vehicles.

Starting with Tranche 1, each spiral will also include some experimental satellites used to mature new payloads for communications, remote sensing, position navigation and timing, and more advanced onboard computing.

Tranche 0 Flight 1 payload stack, with two SpaceX Tracking Layer satellites on top and eight York Transport Layer satellites below. (Credit: York Space Systems)

Tranche 0 (the Warfighter Immersion tranche) is focused on demonstrating the procurement, deployment, and operation of a minimum viable product. The agency moved quickly to begin procuring this first tranche, with contracts for the Transport Layer, Tracking Layer, and launch awarded by the end of 2020.

The Tranche 0 Transport Layer contracts for 20 satellites were awarded on Aug. 31, 2020, at the cost of about $280 million; this contract awarded 10 satellites each to Lockheed Martin ($187 million) and York ($94 million). The Tracking Layer contracts for eight satellites were awarded on Oct. 5, 2020, at a total cost of about $350 million, with four satellites each to L3Harris ($194 million) and SpaceX ($149 million). While most of the satellites are sized to be mounted on ESPA rings to form the payload stack, the SpaceX satellites are larger and will be placed on top of the ESPA rings.

Ground systems for Tranche 0 are being provided through collaboration with the Naval Research Laboratory, which also supports interoperability testing of the OISL hardware from various vendors. There are now seven ground entry points for the network, with four in Alaska, two in Maryland, and one overseas.

The satellites from the first launch are well into their commissioning processes. The two Tracking Layer satellites from SpaceX have passed their bus checkouts, raised their orbits, and achieved first light on their infrared imaging payloads about two months after launch.

The York satellites have gone through their bus checkouts and are preparing to test their Link 16 communications payloads. One satellite was found to have a workmanship issue that does not prevent it from performing the mission but will limit its capacity. Link 16 has not been used through satellites in the past, and SDA is currently working its way through the federal frequency coordination processes for the new usage of this tactical communications protocol. Orbit raising for the York satellites will take place after the initial Link 16 payload testing.

Work has begun on the initialization of the optical inter-satellite link payloads for the spacecraft from the first launch. Testing of the optical links may begin later this year.

Falcon 9 after launching the Crew-7 mission. (Credit: SpaceX)

Future tranches are already underway. Tranche 1 is to provide an initial warfighting capability. Features of Tranche 1 are regional persistence for tactical data links, advanced missile detection, and beyond-line-of-sight targeting. Tranche 2, following two years after Tranche 1, will provide global persistence for all of the functionality in Tranche 1 and incorporate lessons learned from operating Tranche 0.

All of the contracts for Tranche 1 have been awarded and procurement of Tranche 2 is under way. SDA recently awarded contracts worth approximately $1.5 billion to Lockheed Martin and Northrop Grumman for a total of 72 Beta variant satellites in the Tranche 2 Transport Layer. Bids have also been received for 100 Alpha variant satellites for the Tranche 2 Transport Layer, which will be split between two vendors.

Starlink Group 6-13

Despite the delay to the SDA launch, SpaceX will launch yet another Starlink mission from Space Launch Complex 40, at the Cape Canaveral Space Force Station, in Florida. Liftoff is currently scheduled for Aug. 31, at 7:52 PM EDT (23:52 UTC); in the event of a delay, several backup T0s are available, with the launch window open until 1:01 AM EDT (05:01 UTC), and a backup launch window 24 hours later.

The booster supporting this mission, B1077-7, has supported the Crew-5 mission, GPS III SV06, Inmarsat I-5, CRS-28, Galaxy 37, and one Starlink mission. Following the launch, it will attempt landing on SpaceX’s drone ship A Shortfall of Gravitas, which will be stationed roughly 640 kilometers downrange. It was tugged by Crosby Skipper, which has been used to support a large number of missions while SpaceX’s multi-purpose recovery vessel Bob is out for maintenance.

SpaceX’s other recovery vessel Doug will be attempting to recover both fairing halves on this mission. It is unknown if these fairings are flight proven or not; however, it is probably given over 90% of fairings this year have been flown before.

This mission will place 22 Starlink v2 Mini satellites into a 285 by 293-kilometer low-Earth orbit, inclined 42.99 degrees. The satellites will spend the following months raising their orbits to the operation 530-kilometer circular low-Earth orbit, inclined 43.00 degrees.

(Lead image: Falcon 9 on SLC-4E ahead of the SWOT mission. Credit: Jack Beyer for NSF)