1
$\begingroup$

According to the recent Spaceflight Now article Rocket Lab updates launch window for first commercial mission:

The Irvine01 and NABEO payloads will join two CubeSats for Spire Global, and one nanosatellite for GeoOptics that were already booked on the upcoming Electron launch.

The Spire and GeoOptics payloads will measure GPS satellite navigation signals passed through Earth’s atmosphere to derive information about weather and climate.

The flight profile for the launch next month will place the satellites into an orbit ranging between 155 miles and 310 miles (250 kilometers and 500 kilometers) at an inclination of 85 degrees, then the Electron’s Curie kick stage will circularize the orbit, according to Rocket Lab.

Rocket Lab’s fourth launch, set to follow soon after the next mission, will be dedicated to launching CubeSats sponsored by NASA and developed by U.S. research institutions.

Since "orbit" is singular, I'm assuming that the satellites will be deployed along a single 250x500 km orbit (i=85°). After that, "...the Electron’s Curie kick stage will circularize the orbit..."

Question: Why does Rocket Lab plan to shoot first, ask questions later deploy first, circularize later?

According to Rocket Lab's article Rocket Lab successfully circularizes orbit with new Electron kick stage:

Rocket Lab CEO and founder Peter Beck says the kick stage opens up significantly more orbital options, particularly for rideshare customers that have traditionally been limited to the primary payload’s designated orbit.

“Until now many small satellite operators have had to compromise on optimal orbits in order to reach space at an accessible cost. The kick stage releases small satellites from the constricting parameters of primary payload orbits and enables them to full reach their potential, including faster deployment of small satellite constellations and better positioning for Earth imaging,” Beck says.

The kick stage is designed for use on the Electron launch vehicle with a payload capacity of up to 150 kg and will be used to disperse CubeSat constellations faster and more accurately, enabling satellite data to be received and utilized sooner after launch.

Equipped with a precision pointing cold gas reaction control system, the kick stage also has its own avionics, power and communications systems.

So deploying before circularizing seems to defeat the purpose.

The Curie kick-stage can be seen in the answer(s) to What is Rocket Lab's new Curie “Kick Stage”?

$\endgroup$
  • $\begingroup$ Could the target orbit be the 250x500km one ? It would makes sense if one wants to observe the GPS signals passing through the atmosphere to have an orbit as low as possible. $\endgroup$ – Antzi May 28 '18 at 5:30
  • $\begingroup$ @Hobbes I see, so "...will place the satellites into an orbit ranging between..." might better be worded as "...place the Curie Kick Stage, together with all of the satellites..." If that can be verified, and it's not just one more test of the Kick Stage alone, then it's probably the answer. $\endgroup$ – uhoh May 28 '18 at 6:55
7
$\begingroup$

Spaceflight Now uses the word 'deploy' in an unusual sense. We normally expect it to mean 'separate the payload from the rocket', but here they mean 'separate the combination of kickstage and payloads from the second stage'.

So all the satellites end up in a circular orbit.

From RocketLab's site:

These new payloads join existing ‘It’s Business Time’ customers, including two Lemur-2 satellites from Spire Global and a GeoOptics Inc. satellite, built by Tyvak Nano-Satellite Systems. The payloads will be launched to a 500km x 250km elliptical orbit at 85 degrees, before being circularized using Rocket Lab’s Curie engine powered kick stage.

so as I suspected: the second stage launches into an elliptical orbit. Then the Curie stage with payloads separates from the second stage, the Curie stage circularizes the orbit and then deploys the payloads.

$\endgroup$
  • $\begingroup$ Very nice, thank you! I wonder if they are going out of their way to avoid using the word 'deploy' for some reason. It does not actually say deploy, release, or anything similar. $\endgroup$ – uhoh May 28 '18 at 9:32
  • $\begingroup$ I don't see how this answers the question of "why?", it just restates the question in other words. $\endgroup$ – djr May 28 '18 at 21:40
  • 2
    $\begingroup$ It answers the question by saying they don't deploy first, circularize later. The word "deploy" was badly chosen by Spaceflight Now. $\endgroup$ – Hobbes May 29 '18 at 6:40

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.