By continuing to use this site, you agree to the use of cookies. You can find out more by following this link Accept & Close ›
SSTL
Space Blog

Side-eject a spacecraft from a rocket? No problem.

How clever mechanical design was the key to getting CARBONITE-1 into orbit.
A couple of years ago the space industry saw a shift in the downstream market for space data with new start-ups attracting investment for novel space-based applications and many of these new applications will require daily-revisit earth observation data from constellations of low-cost, rapid-build, satellites to close their business case. 
 

A launch opportunity requiring a bespoke deployment mechanism

With this in mind, in 2014 we began developing plans for a new low-cost, rapid-build micro-satellite technology demonstrator that would carry a Commercial-Off-The-Shelf (COTS) telescope and HD video to orbit.  We called the new micro-satellite platform CARBONITE-1, and as the platform designs began to come together we identified an ideal opportunity to launch CARBONITE-1 together with our three DMC3/TripleSat satellites on board ISRO’s PSLV-XL launch vehicle.  We were immediately in “All systems go” mode with just 6 months to complete the build and 2 major challenges to overcome: we had to build the new microsatellite with very tight size and weight constraints in order to use the limited available space below a large deck on the rocket, and we had to design a completely new deployment mechanism that would eject the spacecraft sideways (instead of the usual “release-and-slide” mechanism), to prevent it from hitting the upper deck of the launch adaptor.

 
Graphic showing CARBONITE-1 mounted on the PSLV-XL rocket, and the approximate side-eject angle required for safe delivery into orbit

At SSTL we are very used to working with complex size and weight constraints for our customers, so the platform design itself was a fairly routine engineering challenge – however designing a new deployment mechanism from scratch in a 12 week timeframe was a big challenge, but one our engineers relished! 
 

The design

Once we had made the decision to go all-out to take up this launch opportunity for CARBONITE-1, we quickly assembled a team of engineers to work on the new launch deployment mechanism that would be required, and they set to work.  The basic concept of the new deployment mechanism uses spring loaded lever arms of different lengths to impose an angular motion, with a set of rollers on the side of the rocket engaging with C-sections on the spacecraft.  The design includes micro-switches, links guides, and stops which act together to prevent movement in the axial direction with respect to the launch axis, prevent premature release during motion, and to define the rotational speed of the spacecraft as it leaves the rocket. 

As the project progressed, the engineers identified additional challenges.  Due to the low rotation rates of the spacecraft at the point of ejection, and the physical position of equipment around the separation panel, work had to be done to eliminate any potential clashes between the spacecraft, the separation ring and panel, and the side of the rocket.  We used 2D analysis to size the link lengths, check the C-section geometry, release angles and torques of the springs and achieved a theoretical successful separation of the spacecraft.  We then undertook sensitivity analysis to demonstrate that, even with different torque values, successful separation was still achieved. 
 

The test campaign

Theory complete, the engineers built the new deployment mechanism with majority COTS components to keep costs down and for a rapid build schedule.  Our first test campaign was to vibrate the new deployment mechanism attached to the spacecraft to check that all the mechanics and components would hold intact during the rigors of a launch.  Next the mechanism underwent thermal cycling and finally we were ready to move on to the most exciting, but nerve-wracking test - simulating, as accurately as possible, the process of firing the spacecraft off from a rocket. 
 

Deployment testing

For this next phase of testing we attached the deployment mechanism to an old separation ring, using a clear plastic separation panel to allow us to view the link arms in action.  To this rigged up separation and deployment assembly, we suspended a mass dummy representing the CARBONITE-1 spacecraft using 4 long strops attached via a horizontal lifting frame to a single cable over 10m high suspended from one of our overhead cleanroom cranes.  A laser and a Go-Pro camera were mounted on the front of the mass dummy, projecting onto a grid laid out on the floor of the cleanroom so that a video of the laser movement profile could be mapped for later co-ordination with the analysis. 

Birds-eye view of deployment test setup

Numerous deployment tests were performed and all were successful, allowing us to replace the mass dummy with the real CARBONITE-1 spacecraft, and again we were very relieved and pleased that all the deployment tests went smoothly and to plan. 
 

 

Launch authority sign-off

The new deployment mechanism design and test results were presented to our colleagues at ISRO/Antrix, the launch agency, and were passed for launch authority sign-off.  We were all systems go for launch.  

CARBONITE-1 (bottom left) attached to the separation ring, below the upper deck of PSLV-XL launcher
 

Success!  Textbook side-ejection achieved!

On 10th July 2015, CARBONITE-1 was successfully ejected from the PSLV-XL rocket, to begin its mission lifetime in orbit.  Initial data from the magnetometers on board the satellite recorded a day after launch showed that spin rates were up to around 15 degrees / second max around any axis, which was a very acceptable result. 

CARBONITE-1 is operational in orbit, and is delivering images and video, proving the COTS technologies on board for future missions. 

Future CARBONITE and nanosatellite missions are in the pipeline at SSTL, so we may need our side-ejecting deployment mechanism again in the future – or a variant – and if we do, we’ll be ready to meet the challenge.  
 

 

 
 

 

 

19 November 20150 Comments1 Comment

Back to Blog

Comments
Blog post currently doesn't have any comments.

About This Blog

SSTL's lowdown on cost effective space technology, small satellites, space science and interplanetary exploration.

Post Archive

May 2017(1)
January 2017(2)
October 2016(3)
September 2016(1)
July 2016(1)
June 2016(1)
April 2016(1)
March 2016(4)
February 2016(3)
December 2015(2)
November 2015(3)
October 2015(3)
July 2015(1)
May 2015(0)
May 2015(1)
April 2015(1)
March 2015(2)
February 2015(2)
January 2015(2)
December 2014(1)
November 2014(2)
October 2014(2)
September 2014(1)
July 2014(2)
June 2014(3)
May 2014(1)
April 2014(1)
March 2014(1)
February 2014(2)
January 2014(2)
November 2013(3)
October 2013(2)
September 2013(2)
July 2013(3)
June 2013(2)
May 2013(2)
April 2013(4)
March 2013(1)
February 2013(3)
January 2013(5)
December 2012(6)
November 2012(5)
October 2012(4)
September 2012(4)
August 2012(1)
July 2012(6)
June 2012(1)
May 2012(2)
April 2012(5)
March 2012(3)
February 2012(3)
January 2012(1)
December 2011(1)
November 2011(4)
October 2011(5)
September 2011(4)
August 2011(3)
July 2011(4)
June 2011(6)
May 2011(3)
April 2011(1)
March 2011(3)
February 2011(2)
January 2011(3)
December 2010(2)
November 2010(1)
October 2010(2)
September 2010(4)
August 2010(4)
July 2010(2)
June 2010(2)
May 2010(2)
April 2010(4)
March 2010(4)
February 2010(4)
January 2010(3)
December 2009(2)
November 2009(5)
October 2009(2)
September 2009(6)
August 2009(4)
July 2009(3)
June 2009(1)
May 2009(2)
March 2009(2)
February 2009(5)
January 2009(2)
December 2008(3)
November 2008(6)
October 2008(5)
September 2008(3)
August 2008(5)
June 2008(1)
May 2008(3)
April 2008(5)
March 2008(1)
February 2008(1)
January 2008(3)
December 2007(3)
November 2007(6)
October 2007(3)
September 2007(3)
August 2007(1)
July 2007(1)
June 2007(2)
May 2007(2)
April 2007(1)
January 2007(3)
December 2006(1)
September 2006(1)
May 2006(2)
January 2006(1)
December 2005(7)

Show/Hide All

If you like Space Blog, why not subscribe by RSS by clicking the subscribe button, or to recieve updates by email click the subscribe by email button.


*Comments Policy
SSTL reserves the right not to publish comments if they are deemed inappropriate.