The Curie Kick Stage and "Deorbit-Washing"

[Pueo]

With the news that the next Electron launch will include a double stack payload adapter that will end up as orbital debris in a 450x450 km orbit, I decided to take a look to see to what extent the de-orbit burns Rocket Lab says it performs with its kickstage have shortened their orbital life span.  The answer is pretty disappointing.
To date only one kick-stage has re-entered: the kick stage from the 10^th launch ("Running Out of Fingers") which reentered in November 2020.  Additionally, only one other kick-stage is predicted to reenter soon, the 5^th launch ("Two Thumbs Up") which is predicted to reenter this July.

These launches are also not the norm for Electron launches, with their destination orbits being below the normal 500 km SSO orbit targeted by Rocket Lab's customers.  The vast majority of kickstages remaining in orbit have perigees above 480 km, and two have an apogee above 1200 km.  The kickstages are generally in eccentric orbits, so what appears to be happening is that Rocket Lab performs their "deorbit burn" with the fuel they have left, but continue to load up on rideshare payload past the point where there's enough performance to de-orbit the kickstage in a reasonable time.
Also concerning is that three of the electron second stages have yet to decay.  While two are from the most recent launches, the other is from October 2019 and is likely to take a while to come down thanks to its 1122x311 km orbit.

While Rocket Lab is by far not the worst offender when it comes to space junk, it's disappointing to see from a company that promotes itself as a responsible steward of space.  I call this practice "deorbit-washing" (similar to greenwashing) where a launch company markets its debris management practices as more effective than they actually are.  If someone can come up with a better name I'm all for it, can't really think of a color for the practice of preventing space debris.

[trimeta]

Not sure if you got this from the following tweet (and its replies) which includes the orbital heights of all remaining Electron kick stages, but even if you did, it's a good source for others interested in reading about the details.

https://twitter.com/planet4589/status/1392322865316442114

[Stan-1967]

I call this practice "deorbit-washing" (similar to greenwashing) where a launch company markets its debris management practices as more effective than they actually are.  If someone can come up with a better name I'm all for it, can't really think of a color for the practice of preventing space debris.

How about "Time Based Orbital Mass Balance Deficit", which sounds complicated but can be reduced to the Acronym T-BOMB'D, which maybe captures the essence of a disaster mode for LEO.    Mathematically it would be the ratio of  what goes up vs. what comes down.  As what comes down goes to zero, the TBOMB'D ratios goes to infinity.  It could also bracket the ratio for 1 yr, 5yr, 10 yr, 100 yr 1000yr ratios.

Irresponsible actors in LEO Space would have a very high T-BOMB'D ratio's and could be called out publicly for T-BOMB'D ing LEO.

You didn't ask for simplicity...  :-)

[Pueo]

Not sure if you got this from the following tweet (and its replies) which includes the orbital heights of all remaining Electron kick stages, but even if you did, it's a good source for others interested in reading about the details.

https://twitter.com/planet4589/status/1392322865316442114

Jeeze I wish I had, I wouldn't have spent an hour staring at space-track.org trying to find the two kick-stages and two Photons that don't show up if you just search for "Electron Kick Stage".  Thanks for posting this, it really helps show how the two kick stages that have or are about to re-enter are the exception rather than the norm.

[gaballard]

The Photon is tiny, really really tiny compared to just about everything else up there (barring the payloads it deploys, CubeSats, etc.), and a rounding error compared to the size of LEO.

The Electron's diameter is only 1.2m (3'11"), and the Photon kick stage's height is some fraction of the 2.4 m (7 ft 10 in) second stage.

A typical Boeing communication satellite bus (the 702SP is pictured) is 4.57m (15') tall and 2.1m (7') wide.

Back of the napkin math puts the total volume of space between 100km and 700km at 336,000,000,000km, or 336 trillion meters.

Not that space junk isn't an issue, but Photon's contribution is a rounding error at best.

[edkyle99]

Search for any other company's upper stage (even THAT company, yes) and you will find dozens of examples still orbiting.  In some cases, those stages have broken into dozens to thousands of pieces of debris which are still being tracked.

 - Ed kyle

[Lars-J]

The Photon is tiny, really really tiny compared to just about everything else up there (barring the payloads it deploys, CubeSats, etc.), and a rounding error compared to the size of LEO.

The Electron's diameter is only 1.2m (3'11"), and the Photon kick stage's height is some fraction of the 2.4 m (7 ft 10 in) second stage.

A typical Boeing communication satellite bus (the 702SP is pictured) is 4.57m (15') tall and 2.1m (7') wide.

Back of the napkin math puts the total volume of space between 100km and 700km at 336,000,000,000km, or 336 trillion meters.

Not that space junk isn't an issue, but Photon's contribution is a rounding error at best.

With that math *any* space junk is a rounding error at best. 

But a tiny bullet is still lethal. They should do better - all companies and nations should do better.

While Rocket Lab is by far not the worst offender when it comes to space junk, it's disappointing to see from a company that promotes itself as a responsible steward of space.  I call this practice "deorbit-washing" (similar to greenwashing) where a launch company markets its debris management practices as more effective than they actually are.  If someone can come up with a better name I'm all for it, can't really think of a color for the practice of preventing space debris.

.

Yes, RL should be more up front about this.

[Alberto-Girardi]

The Photon is tiny, really really tiny compared to just about everything else up there (barring the payloads it deploys, CubeSats, etc.), and a rounding error compared to the size of LEO.

The Electron's diameter is only 1.2m (3'11"), and the Photon kick stage's height is some fraction of the 2.4 m (7 ft 10 in) second stage.

A typical Boeing communication satellite bus (the 702SP is pictured) is 4.57m (15') tall and 2.1m (7') wide.

Back of the napkin math puts the total volume of space between 100km and 700km at 336,000,000,000km, or 336 trillion meters.

Not that space junk isn't an issue, but Photon's contribution is a rounding error at best.

With that math *any* space junk is a rounding error at best. 

But a tiny bullet is still lethal. They should do better - all companies and nations should do better.

While Rocket Lab is by far not the worst offender when it comes to space junk, it's disappointing to see from a company that promotes itself as a responsible steward of space.  I call this practice "deorbit-washing" (similar to greenwashing) where a launch company markets its debris management practices as more effective than they actually are.  If someone can come up with a better name I'm all for it, can't really think of a color for the practice of preventing space debris.

.

Yes, RL should be more up front about this.

I agree.

Terrorism about space debris should be avoided, but everyone should do better. Lucly spaceX does the deorbits, otherwise we would have ended up with a pile of second stages. But ultimately I think we could excuse RL for the electron, given the big penalty of a full deorbit. But since these objects are integers and tracked and aren't so much The risk for an active mission striking one of them is very low.Although for a dead satellite the risk is bigger, because it can't manovrate. But being in polar orbit makes them more dangerouse.

[Lars-J]

I agree.

Terrorism about space debris should be avoided, but everyone should do better. Lucly spaceX does the deorbits, otherwise we would have ended up with a pile of second stages.

Although about SpaceX... Yes as Ed points out, not all SpaceX upper stages are de-orbited. They try to do it for all LEO missions, but sometimes the deorbit burn fails. And they don't do de-orbit burns for GTO missions.

But ultimately I think we could excuse RL for the electron, given the big penalty of a full deorbit. But since these objects are integers and tracked and aren't so much The risk for an active mission striking one of them is very low.Although for a dead satellite the risk is bigger, because it can't manovrate. But being in polar orbit makes them more dangerouse.

LV size doesn't make a difference, the delta-v for de-orbit is the same. What does affect RL more though is that since their payloads are much smaller they usually don't have their own maneuvering capability, so they need to be dropped off in higher/operational orbits which makes upper stage deorbit more difficult. (Whereas *most* SpaceX LEO payloads are dropped off at lower altitudes)

[Alberto-Girardi]

I agree.

Terrorism about space debris should be avoided, but everyone should do better. Lucly spaceX does the deorbits, otherwise we would have ended up with a pile of second stages.

Although about SpaceX... Yes as Ed points out, not all SpaceX upper stages are de-orbited. They try to do it for all LEO missions, but sometimes the deorbit burn fails. And they don't do de-orbit burns for GTO missions.

Have they ever released a statement about that?

Do they at least place these second stages in the graveyard orbit?

[Asteroza]

One could make the argument that for safety reasons they need to transition to all Photon, as that allows more loiter capability to align deorbit burns, plus to reduce fuel consumption, use something like a deorbit electrodynamic tether (AKA generator mode) to get Photon lower before the burn.

[LouScheffer]

Although about SpaceX... Yes as Ed points out, not all SpaceX upper stages are de-orbited. They try to do it for all LEO missions, but sometimes the deorbit burn fails. And they don't do de-orbit burns for GTO missions.

For the GTO missions, at least recently, they've been leaving the second stage in an orbit with a low perigee.  It then re-enters within at most a few years, so leaving no space debris.  For example, the second stage of Es'hail was left in a 208 x 37695 km orbit, and decayed within 6 months:
FALCON 9 ROCKET BODY (ID 43701)
Type: Rocket Body
Mission: Es’hail 2 Television Satellite
Launched:    Nov 15, 2018
Re-entered: Apr 15, 2019

[Pueo]

One could make the argument that for safety reasons they need to transition to all Photon, as that allows more loiter capability to align deorbit burns, plus to reduce fuel consumption, use something like a deorbit electrodynamic tether (AKA generator mode) to get Photon lower before the burn.

Yep, the ideal is to have one of the payloads remained attached to the kick-stage for launches without enough performance to quickly deorbit, as it immediately cuts the number of orbital objects by 1.  Of course most payloads aren't designed to remain attached to a dumb hefty stage with the complications to attitude control, thermal management, and power that that entails, so you're usually only going to get customers to keep the payload attached to the kick-stage if the kick-stage serves as the satellite bus.