Launch Vehicle Separation Systems 101

Building a satellite is a costly and difficult endeavor. Getting that very expensive and sensitive payload safely on orbit is the next step. That’s where we come in. And once we get them to orbit, we need to separate them and send them on their way. So, we work with our customers to identify the right separating system to deploy their spacecraft. While sometimes customers come to us with a system chosen, more often we consider the size and shape of their spacecraft, make a recommendation and purchase it for them. There are many benefits for the customer to go this route. First of all, we’re subsystem agnostic. We choose the right system for the mission, period. We don’t sell hardware – we can pick and choose from a variety of vendors looking for the best technical solution and value to the customer. Here’s a brief rundown of the available options:

Clamp bands: These type of separation systems used two rings, held together by a clamping mechanism. One ring is attached to the spacecraft and one to Spaceflight’s mounting structure. Once the clamping mechanism is released, the rings separate and the spacecraft is flying free. Springs are used to provide a separation velocity to the spacecraft. They come in a variety of bolt circle diameters and are the most common method for separating larger spacecraft. Within the general category of clamp bands, there are different approaches to the clamping mechanism:

Motorized Light Band by Planetary Systems Corporation
Motorized Light Band by Planetary Systems Corporation

Motorized Light Band (MLB): The MLB is a popular separation system, which is built by Planetary Systems Corporation. It uses a motor to release an innovative modular clamping mechanism. It is very reliable, lightweight, and cost effective solution.. We are using multiple MLBs of different diameters for our SSO-A launch. It’s highly reliable and has been flight proven many times. It is lighter than a clamp band.

Marmon Clamps: Marmon clamps are classic mechanisms for holding together and releasing cylindrical structures, including the difference stages of some rockets. They consist of two rings with a V-shaped groove in them. They clamp on a corresponding V-shaped ridge that is formed when bringing the two separating halves together. The two rings are held torqued tightly in place by a bolt mechanism that can be separated by various means. For a spacecraft separation system, one side would bolt to the spacecraft and one to the launch vehicle. Traditionally, separation systems of these type used pyrotechnic (i.e. explosive) devices to cut the clamping bolt. However, the more modern systems such as Spaceflight uses, a low shock release mechanism is used to give our customers a gentle separation. They have an excellent success rate. We are using a large one, with a 1575 mm diameter from Ruag for an upcoming mission.

For CubeSats we use a variety of dispensers depending on the needs of individual Cubesats, as well as to help fit as many spacecraft as possible onto a given launch.


Quadpack: The Quadpack is built by Innovative Solutions in Space (ISIS) in Delft, Holland. They can handle up to 12U equivalent volume of cubesats. In other word, different combinations of CubeSat sizes that add up to 12Us. For example it can dispense four 3U satellites, or two 6U satellites, two 3Us plus 1 6U or a single 12U. We’re using Quadpacks on both the SSO-A mission and PSLV mission.

6U pack: This is also built by our friends in Delft. It is basically half of a Quadpack. We are using several of these on an upcoming launch on a Minotaur IV launch vehicle, as well as on the SSO-A mission.

ISI pod: We’ve also used the single 3U “ISI pod” dispenser built by the Dutch company ISIS for Soyuz missions.

PSL-P by Astrofein

PSL-P (Pico Satellite Launch Pack): This is another dispenser, similar to the Quadpack in size and capacity. It is built by German company Astro Fein. It holds up to 12U of CubeSats in different combinations. It features a clamping mechanism that holds the CubeSats firmly in place once the doors are closed prior to flight.

Canisterized Satellite DIspenser (CSD): The CSD is built by Planetary Systems Corporation, who also build the MLB separation systems discussed above. This dispenser design comes In multiple sizes, 3U, 6U, and 12U. It has a unique restraint mechanism. Instead of using rails inside the dispenser, it has tabs along the bottom of the CubeSat that are clamped in place when the door is closed. This provides a firm attachment and known load path, provide more definitive knowledge of the CubeSat dispensers.

Custom systems: Sometimes the commercial off the shelf solutions don’t work with a customer’s spacecraft or they have their own unique system. In these cases, we are flexible and adapt as needed. For the Hawkeye360’s upcoming payload, they have a special dispenser unit, that slides the satellite out for deployment. We are accommodating the unique requirements to work with this systems. In other situations, we’ve also created custom deployment units to meet unique criteria on the PSLV and the DNEPR launch vehicles.

One of the most common questions we get is about the tip off rate – how the deployment will “tip” the spacecraft or cause it to alter course from it’s path. Standard separation systems like lightbands and clamp rings will have little tip off and this rate can be adjusted based on the springs activated during deployment. Dispensers are typically less refined dynamically will have a higher tip off rate.

These are just some of the possible separation systems available. Our experts can find exactly the right one for your spacecraft – it can be like a game of Tetris making the pieces all fit. But that is why our customers rely on us to get their spacecraft safely on orbit.

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