4
$\begingroup$

The Verge's How small launcher Rocket Lab plans to pull off its first mission to the Moon next year says (though this has since been addressed):

Photon is going to need it all in order to get NASA’s CAPSTONE into the Moon’s orbit. After launching from Rocket Lab’s new launch site in Virginia, Electron will first deploy the Photon spacecraft — with the CAPSTONE satellite mounted on top — into a low circular orbit around Earth. From there, Photon will slowly stretch its orbit, taking the vehicle farther away from the planet. Eventually, Photon will burn its HyperCurie engine and set it on a course toward the Moon. All in all, it’ll take about eight to nine days to reach the right spot where Photon will deploy the CAPSTONE spacecraft, and Stiles says the route they’re taking will save Rocket Lab some energy along the way. “That’s a pretty key enabler for the mission,” says Stiles.

It's not uncommon to raise the apogee of an uncrewed spacecraft starting from LEO in several steps rather than one long burn. See for example

and possibly these low-energy transfer-related questions

Eight to nine days is tiny for a mission that will likely last several years, there's no food or water to run out as there would be for a crewed mission.

I'm just wondering if the eight or nine days is due to several apogee-raising burns at perigee, or if it's just one or two plus the delay associated with the natural slowing way down near the Earth-Moon L1 point on a low-energy transfer between Earth's sphere of influence and the Moon's.

Question: How many times will the Photon fire its Curie in order to "reach the right spot" to deploy CAPSTONE towards the Moon? If known, which apogee will it reach after each one?


Footnotes:

The block quote may be misleading. This comment states:

...NASA is paying for CAPSTONE, just as it is paying for the launch, but the spacecraft idea came from Advanced Space, it is owned by Advanced Space, all of the mission design and payload has been researched literally for years by Advanced Space, and all of the flight dynamics operations will be handled by Advanced Space

$\endgroup$
2
  • 1
    $\begingroup$ If I may request an edit, NASA is paying for CAPSTONE, just as it is paying for the launch, but the spacecraft idea came from Advanced Space, it is owned by Advanced Space, all of the mission design and payload has been researched literally for years by Advanced Space, and all of the flight dynamics operations will be handled by Advanced Space. $\endgroup$
    – ChrisR
    Sep 6, 2020 at 20:52
  • 1
    $\begingroup$ @ChrisR I've made a note of that. I can't modify the block quote but I can call it into question. I'll look now, and if I find a more suitable item to quote I'll toss this one completely, and I may ask a separate question about CAPSTONE itself where this can be addressed as an answer. Thanks! $\endgroup$
    – uhoh
    Sep 7, 2020 at 0:16

1 Answer 1

2
+100
$\begingroup$

With the most recent update by Rocket Lab, posted on various social media including Facebook on Friday 1 July (about five minutes prior to this answer being written!), Photon will perform a total of seven burns out of a planned eight, with the sixth burn doing the job of two burns at the same time.

The Moon just got a little closer! We've successfully ignited Photon's Hyper-Curie engine a 6th time, raising #CAPSTONE's apogee to 69,680 km. Since we combined 2 burns into 1 in this maneuver, only 1 final burn remains to set CAPSTONE on a ballistic lunar transfer to the Moon.

The next and final burn is designed to set CAPSTONE on a ballistic lunar transfer trajectory to the Moon travelling at 24,500 mph (39,400 km/h) to break free of Earth's orbit. This final maneuver is scheduled to take place as early as July 4th.

(also tweeted)

The press kit for CAPSTONE on Rocket Lab's website states that the final burn and deployment are expected six days after launch, deployment occurring "within 20 minutes of the final burn".

Given the earlier reporting also suggested launch would occur from Virginia USA, rather than Mahia Peninsula NZL, it seems likely that several deliberate changes were made during the time between, and, with the merging of two burns already, after launch as well.

$\endgroup$
2

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

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