Author Topic: Refueling Photon (and/or Electron upper stage)  (Read 8172 times)

Offline Robotbeat

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Refueling Photon (and/or Electron upper stage)
« on: 09/15/2020 03:37 pm »
This is a thread to discuss Rocketrepreneur's idea here:
The payload of Photon is limited due to it starting at LEO with 300kg when launched on Electron. Use 1000kg LV like Firefly Alpha and it could be 300kg at earth escape. This could be done with combination of kickstage and delivery to higher orbit by LV.

Something to consider for any follow on missions.
RocketLab has already increased their payload and may have more payload increases planned. Also, an electric ion/plasma propulsion stage would be a good fit for this and should allow even higher performance, although even just a Photon with stretched tanks should allow significant payload to Venus. The Pioneer Venus small probes each weighed only 90kg, and we could probably do less nowadays even with a parachute. With the kick stage operating as the relay satellite, there's a very large savings in both cost and mass.

This mission isn't going to use Firefly Alpha.

In-space refueling of the Electron second stage and Photon would get you most of the way to 300kg to a Trans Venus Injection trajectory (if the previous analysis we did in an AAS depot paper on refueling a VO LauncherOne class upper stage/kick stage is any indication). I'd love to run the numbers for Electron/Photon, but have so far been too busy.

~Jon


And here:


The payload of Photon is limited due to it starting at LEO with 300kg when launched on Electron. Use 1000kg LV like Firefly Alpha and it could be 300kg at earth escape. This could be done with combination of kickstage and delivery to higher orbit by LV.

Something to consider for any follow on missions.
RocketLab has already increased their payload and may have more payload increases planned. Also, an electric ion/plasma propulsion stage would be a good fit for this and should allow even higher performance, although even just a Photon with stretched tanks should allow significant payload to Venus. The Pioneer Venus small probes each weighed only 90kg, and we could probably do less nowadays even with a parachute. With the kick stage operating as the relay satellite, there's a very large savings in both cost and mass.

This mission isn't going to use Firefly Alpha.

In-space refueling of the Electron second stage and Photon would get you most of the way to 300kg to a Trans Venus Injection trajectory (if the previous analysis we did in an AAS depot paper on refueling a VO LauncherOne class upper stage/kick stage is any indication). I'd love to run the numbers for Electron/Photon, but have so far been too busy.

~Jon

Sorry, how would in space refuelling of an expendable rocket work? Are you proposing multiple expendable tanker launches to top up the spacecraft propellant tank in orbit?

I should've been clear that I wasn't suggesting this for their 2023 mission, but as a way to improve capabilities for future missions. I was referring to having the Electron Stage 2/Photon/Payload stack dock with a microsatellite launcher refueling depot, which would be topped up from buying excess propellant from bigger launchers as per this AAS paper (reviewed at https://selenianboondocks.com/2018/09/aas-paper-review-raan-agnostic-3-burn-departure-methodology-for-deep-space-missions-from-leo-depots-part-1-of-2/ and https://selenianboondocks.com/2018/09/aas-paper-review-raan-agnostic-3-burn-departure-methodology-for-deep-space-missions-from-leo-depots-part-2-of-2/). I realize that this probably isn't the thread to get into the merits of that particular concept, I was just mentioning it for context about how they could upgrade their capacity pretty dramatically with only minor changes.

If one of the Mods would like to suggest a better thread for being able to discuss this concept further, that would probably be better than distracting further from the discussion about their 2023 Venus mission.

~Jon
« Last Edit: 09/15/2020 03:38 pm by Robotbeat »
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Offline jongoff

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Re: Refueling Photon (and/or Electron upper stage)
« Reply #1 on: 09/15/2020 04:05 pm »
Thanks Chris. And yes, refueling smallsat launcher upper stages is a hobby horse of mine, though one I'm actively trying to work towards with my current startup.

Key tl;dr summary for those who don't want to read my linked articles:

1- You build a small propellant depot in say an ISS-like LEO, that gets topped-off by buying excess propellant from upper stages of rockets delivering visiting vehicles to the ISS.
2- You launch a smallsat launcher (e.g. Electron)/storable kick stage (e.g. Photon)/BLEO payload stack into LEO, and keep them together. You either have the upper stage or kick stage to rendezvous with the depot (likely guided by the depot), or have a tug bring you to the depot.
3- You refuel the upper stage, kick stage, and if needed the payload via the same fill/drain T-0 QDs as you filled them on the ground. You top up the battery.
4- The now refueled stack departs the depot (either on its own or via tug).
5- The refueled 2nd stage boosts you into a near-escape HEO phasing orbit with a perigee that's aligned with the locus of periapses for the desired departure asymptote (this will require timing when you launch the dedicated mission to the depot so that you can do this at the right time without having to wait long in LEO).
6- You hang out in the phasing orbit(s) for a period of time (typically between 1wk to a month), during which time you do a plane change at apogee that lines your plane up with the departure asymptote, and lowers your perigee for the final departure burn.
7- You now drop down to perigee on the last phasing orbit, and you're in-plane for the departure, with your periapsis in the right place at the right time, so you can do your escape burn with the maximum amount of Oberthy goodness.

I haven't run the numbers for Electron specifically, but when we ran it for Virgin Orbit, you could send a dry payload of something like 90% of LauncherOne's LEO payload onto a Venus trajectory. But I think if the payload needs propellant (say it includes a stage to propulsively brake into Venus orbit), that you could stretch the kick stage a bit more, top the LO upper stage up all the way instead of only part way, and deliver a net payload of probably 80-85% of LauncherOne's LEO payload capacity into Venus Orbit.

Key things you would need to modify on the Smallsat Launcher Upper Stage/Kick Stage to make this feasible:

1- Add in one or more grapple fixtures such as DogTags (or maybe just a DogTag "sticker").
2- Add in ferrous features around the T-0 QDs on the stages to allow for magnetic latching for the in-space refueling version.
3- If you're remote controlling the upper stage, you would need a comms system the depot could talk to, and the software hooks to allow the two to work together.
4- You might have to modify the thruster placement on the kick stage if the upper stage isn't capable of getting to the depot orbit on its own (which may be the case for the current Electron stage), ie modify it so that the kick stage can do circularization and rendezvous while still attached to the payload on one end and the upper stage on the other. For most smallsat launchers this won't be required, but some of the design choices RL has done might make this necessary. Alternately, if the stack can at least get itself into a stable orbit that a tug can rendezvous with, these mods might not be necessary.

You'd still need the depot and tug, but the mods to the rocket can be fairly modest if you're smart about things.

And long-story short, using an architecture like this, you can put most of the mass that you could deliver to the depot LEO orbit into an interplanetary trajectory using such a technique, at maybe 1.5x-2x the cost of just launching to LEO. So for RocketLab, you could be talking about 250kg+ of payload to a Trans Venus Injection orbit for maybe $15-20M. Based on estimates we did for Virgin Orbit -- I haven't had the numbers from RL to run the scenario on their launcher, but those are my guesses at what you could do. It does require a bit step up in infrastructure, but it also provides a big step up in capabilities. And this is for a dedicated smallsat mission where the interplanetary payload completely controls its own destiny.

See the two blog posts in the second quote if you want more details on what I was just saying.

~Jon

Offline TrevorMonty

Re: Refueling Photon (and/or Electron upper stage)
« Reply #2 on: 09/15/2020 06:25 pm »
I still think large kick stage on likes of Firefly Alpha is better and lot less complex option. Forget about refuelling 2nd stage which isn't really design for job without lot modifications. Only advantage to 2nd stage is slight higher ISP engine but extra dry mass may counter that especially as Rutherford and its battery are lot heavier than Hypercurie.

There are few tricks that can be done with Photon based kick stage to save dry mass. Stack would be 300kg mission Photon ontop of 700kg kick stage Photon. Kick stage can be engine + fuel tank, no thrusters, solar panels or smarts as mission Photon would handle all navigation.
Mission Photon could recharge kick stage battery between burns. May even be able to use mission Photon battery to power kick stage engine.

A more complex alternative is have drop tanks for Photon, no kick stage.

While I'm fan of fuel depots, sometimes single launch on bigger LV is easier and cheaper.
Electron is $7m for 300kg, vs Firefly $15m for 1000kg.






Offline jongoff

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Re: Refueling Photon (and/or Electron upper stage)
« Reply #3 on: 09/15/2020 06:59 pm »
I still think large kick stage on likes of Firefly Alpha is better and lot less complex option. Forget about refuelling 2nd stage which isn't really design for job without lot modifications. Only advantage to 2nd stage is slight higher ISP engine but extra dry mass may counter that especially as Rutherford and its battery are lot heavier than Hypercurie.

The second stage has not only higher Isp but also much bigger tanks that you can refuel than Photon does. My guess is refueling just Photon in LEO would likely only get you a modest boost in interplanetary payload capability. Like a 1.5-2x increase instead of a >10x increase.

Quote
While I'm fan of fuel depots, sometimes single launch on bigger LV is easier and cheaper.
Electron is $7m for 300kg, vs Firefly $15m for 1000kg.

Once you add in a big kick stage on Firefly you're probably talking >$20M for a lot less payload than you could get by refueling the upper stages. There are lots of things that are "easier and simpler" that also are way less capable and more expensive.

~Jon

Offline Robotbeat

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Re: Refueling Photon (and/or Electron upper stage)
« Reply #4 on: 09/15/2020 07:19 pm »
It occurs to me that a stretched version of Photon could work as a reusable and refuelable space tug. Since it is designed for long durations, it is fairly well suited for the task, altho i am not sure how well itd do at docking without more thrusters
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Offline TrevorMonty

Re: Refueling Photon (and/or Electron upper stage)
« Reply #5 on: 09/15/2020 07:48 pm »
My hobby horse is Photon for delivering cargo to space station. I can see it being used for emergency spares or high value time critical science experiments. Currently ISS holds 13,000kg of spares, if RL could offer delivery within 2 weeks I'm picking NASA could reduce that spares holding considerably.
Not only do spares take up valuable space but mass also uses additional station keeping fuel.
Spare in orbit may actually be faulty as its been sitting there for years, fresh one delivered from earth would be tested before launch.

This type of service is probably to late for ISS but would ideal for new commercial stations eg Axiom.

Re: Refueling Photon (and/or Electron upper stage)
« Reply #6 on: 09/15/2020 08:24 pm »
Electron has a max payload to LEO of 300 kg per their website. That's using the kick stage, but if we want the second stage to actually make it to LEO, there will probably be a payload hit; I knocked 50 kg off the payload for this estimate, which seemed over zealous, but I figure it's better to over under estimate.

With a fully fueled Electron second stage and a 250 kg payload, I get 5,400 m/s of delta-V. If you could store the LOX all the way to Venus, that would be enough to get there, capture, and even lower the orbit by quite a lot.

Of course, it require you to have 2.15 (metric) tons of propellant on orbit already to fully refuel the second stage.
Wait, ∆V? This site will accept the ∆ symbol? How many times have I written out the word "delta" for no reason?

Offline jongoff

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Re: Refueling Photon (and/or Electron upper stage)
« Reply #7 on: 09/15/2020 09:19 pm »
My hobby horse is Photon for delivering cargo to space station. I can see it being used for emergency spares or high value time critical science experiments. Currently ISS holds 13,000kg of spares, if RL could offer delivery within 2 weeks I'm picking NASA could reduce that spares holding considerably.
Not only do spares take up valuable space but mass also uses additional station keeping fuel.
Spare in orbit may actually be faulty as its been sitting there for years, fresh one delivered from earth would be tested before launch.

This type of service is probably to late for ISS but would ideal for new commercial stations eg Axiom.


Yeah, you'd still need a last-mile solution to handle the rendezvous and prox-ops phases of things, but I'm a big fan of such just-in-time small payload deliveries. I agree though that ISS might be a challenge relative to a commercial station which would likely have higher risk tolerance. We ran the numbers before on using Electron to deliver cargo pods to ISS with a tug like Bulldog handling the last-mile delivery, and it was theoretically competitive with the best of the ISS commercial cargo vehicles on a $/kg basis.

Most people don't realize how much worse the $/kg of net payload delivered to ISS is for most of those vehicles -- it's way higher than the $/kg of just launching something to an ISS-like orbit.

~Jon

Offline jongoff

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Re: Refueling Photon (and/or Electron upper stage)
« Reply #8 on: 09/15/2020 09:22 pm »
Electron has a max payload to LEO of 300 kg per their website. That's using the kick stage, but if we want the second stage to actually make it to LEO, there will probably be a payload hit; I knocked 50 kg off the payload for this estimate, which seemed over zealous, but I figure it's better to over under estimate.

With a fully fueled Electron second stage and a 250 kg payload, I get 5,400 m/s of delta-V. If you could store the LOX all the way to Venus, that would be enough to get there, capture, and even lower the orbit by quite a lot.

Of course, it require you to have 2.15 (metric) tons of propellant on orbit already to fully refuel the second stage.

Yeah, my smallsat launcher refueling depot concept leverages the good $/kg to LEO prices of bigger launchers (especially if you can buy leftover prop from a launcher sending cargo/crew to the ISS) with the on-demand characteristics of a dedicated smallsat launcher.

~Jon

Offline TrevorMonty

Re: Refueling Photon (and/or Electron upper stage)
« Reply #9 on: 09/15/2020 10:03 pm »
Electron has a max payload to LEO of 300 kg per their website. That's using the kick stage, but if we want the second stage to actually make it to LEO, there will probably be a payload hit; I knocked 50 kg off the payload for this estimate, which seemed over zealous, but I figure it's better to over under estimate.

With a fully fueled Electron second stage and a 250 kg payload, I get 5,400 m/s of delta-V. If you could store the LOX all the way to Venus, that would be enough to get there, capture, and even lower the orbit by quite a lot.

Of course, it require you to have 2.15 (metric) tons of propellant on orbit already to fully refuel the second stage.
Best you can hope for is 2nd stage to survive few hours to do earth escape burn.

The fuel depot could top up tanks on Photon or supply it with additional drop tanks. ISP might be lower but no issues with boil off.

Offline Robotbeat

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Re: Refueling Photon (and/or Electron upper stage)
« Reply #10 on: 09/16/2020 12:01 am »
....

Most people don't realize how much worse the $/kg of net payload delivered to ISS is for most of those vehicles -- it's way higher than the $/kg of just launching something to an ISS-like orbit.

~Jon
Right. shuttle wasnt much different in $/kg by this metric! especially if you add shuttles seats.
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Offline TrevorMonty

Re: Refueling Photon (and/or Electron upper stage)
« Reply #11 on: 09/16/2020 12:17 am »
Cygnus and Dragon are around $50k per Kg. Photon on electron should be 100kg plus say $100k kg. Not terrible for equivalent of courier delivery to ISS.

Offline jongoff

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Re: Refueling Photon (and/or Electron upper stage)
« Reply #12 on: 09/16/2020 05:04 am »
Electron has a max payload to LEO of 300 kg per their website. That's using the kick stage, but if we want the second stage to actually make it to LEO, there will probably be a payload hit; I knocked 50 kg off the payload for this estimate, which seemed over zealous, but I figure it's better to over under estimate.

With a fully fueled Electron second stage and a 250 kg payload, I get 5,400 m/s of delta-V. If you could store the LOX all the way to Venus, that would be enough to get there, capture, and even lower the orbit by quite a lot.

Of course, it require you to have 2.15 (metric) tons of propellant on orbit already to fully refuel the second stage.
Best you can hope for is 2nd stage to survive few hours to do earth escape burn.

The fuel depot could top up tanks on Photon or supply it with additional drop tanks. ISP might be lower but no issues with boil off.


Yeah, sorry if I wasn't clear, but you're only using the 2nd stage to get you into a high-apogee, near escape phasing orbit. The rest of the maneuvers, including the final departure burn would be handled with the refueled storable kick stage (e.g. Photon), precisely because most small launchers have second stages that aren't likely to last very long once refueled.

~Jon

Offline Robotbeat

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Re: Refueling Photon (and/or Electron upper stage)
« Reply #13 on: 09/16/2020 04:13 pm »
Cygnus and Dragon are around $50k per Kg. Photon on electron should be 100kg plus say $100k kg. Not terrible for equivalent of courier delivery to ISS.
I wonder, though, since Cygnus and Dragon are carrying mostly pressurized cargo (which reduces their efficiency and increases the cost). Plus, they have a docking/berthing interface which reduces available mass. Probably would cost more like $150-200,000 per kg if you add a miniature docking port.

...what might be interesting would be if you could bring the whole module in via the Bishop airlock then unseal it inside of ISS. That solves the docking port problem mostly (but has other safety issues).
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Offline TrevorMonty

Re: Refueling Photon (and/or Electron upper stage)
« Reply #14 on: 09/16/2020 04:41 pm »
Have detachable cargo pod that goes through bishop airlock. Reattach pod with cargo for disposable orbit.

Reentry of pod maybe possible with small heatsheild and parachutes. Does reduce paload mass but they can earn higher return per mission.

NB there are companies delevoping small rentry cargo pods, night be able to use these.

Offline Robotbeat

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Re: Refueling Photon (and/or Electron upper stage)
« Reply #15 on: 09/16/2020 04:44 pm »
Have detachable cargo pod that goes through bishop airlock. Reattach pod with cargo for disposable orbit...
Yeah, that was my idea with the Bishop airlock.

although, of course, that'd add to cost and reduce payload.
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Offline baldusi

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Re: Refueling Photon (and/or Electron upper stage)
« Reply #16 on: 09/16/2020 05:36 pm »
And what about straight up using the F9 US "as is" after it deploys Dragon? Photon would just attach and let the stage do the LEO burn. If F9 US has enough performance margin, it would be a really low risk approach.

Offline TrevorMonty

Re: Refueling Photon (and/or Electron upper stage)
« Reply #17 on: 09/16/2020 06:11 pm »
And what about straight up using the F9 US "as is" after it deploys Dragon? Photon would just attach and let the stage do the LEO burn. If F9 US has enough performance margin, it would be a really low risk approach.
Rather not turn it into another SpaceX thread.

Offline Comga

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Re: Refueling Photon (and/or Electron upper stage)
« Reply #18 on: 09/17/2020 05:27 pm »
My hobby horse is Photon for delivering cargo to space station. I can see it being used for emergency spares or high value time critical science experiments. Currently ISS holds 13,000kg of spares, if RL could offer delivery within 2 weeks I'm picking NASA could reduce that spares holding considerably.
Not only do spares take up valuable space but mass also uses additional station keeping fuel.
Spare in orbit may actually be faulty as its been sitting there for years, fresh one delivered from earth would be tested before launch.

This type of service is probably to late for ISS but would ideal for new commercial stations eg Axiom.

Reducing the mass of spares on the ISS doesn't change the amount of fuel needed for station reboost.
Reboost is replacing the energy lost to drag, and unless the spares are exterior and protruding, their presence does not impact the drag.  The ISS decelerates slightly less with more mass, and takes more thrust to accelerate. 
It might even be a tiny benefit to have more mass.
Electron and Photon for quick delivery to the ISS still makes sense for other reasons, until the traffic is high enough that the Photon payload equivalent can be carried on passenger or large cargo flights much more frequent than is currently the case.

I still think that residual fuel will be so scattered among all the potential orbits that it won't be practical to scavenge it.
There is one place where residual fuel is plentiful, actually burdensome, and sorely needed, but we don't see that being scavenged. 
(It's in Dragon 2 flights to the ISS, which is off topic for this Refueling Photon thread.)
« Last Edit: 09/17/2020 05:28 pm by Comga »
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Pueo

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Re: Refueling Photon (and/or Electron upper stage)
« Reply #19 on: 09/19/2020 12:04 am »
Some concerns / things that would need to be addressed:

Currently you only have a third of your second stage batteries remaining when you're in orbit, so now either only refuel your second stage to one third full or eat the extra mass penalty of the batteries because there's no way you're recharging the vehicle with solar power after it leaves the depot before the LOX boils off.

The photon/kickstage tanks don't have a QD, they're filled prior to the pad (not to big of an issue, just requires dev time)

Curie / HyperCurie use proprietary propellants, so getting those in a depot supplied by excess fuel might be a tad more complicated.  Alternatively a HyperCurie variant could be developed to use UDMH and N2O4.  It is a quite mature system, but I think RocketLab takes a lot of pride in not using the super nasty stuff, and they would probably only launch the variant from Wallops because of Kiwi environmental concerns.

A route that makes sense to me:
Launch a significantly stretched Hyper Curie UDMH/N2O4 Photon that either has large only partially filled tanks or a set of full normal tanks and an extra set of large empty tanks.  Use a depot filled by the Starliner Service Modules after they detach from their Starliners.  There should be plenty of excess fuel leftover even after boosting back after de-orbiting Starliner if they actually used the full capabilities of the Atlas V CST-100 configuration and don't burn off the LAS system fuel to get to orbit.  This will likely be Starliner only because NASA likely wouldn't want the risk of an unnecessary rendezvous while the capsule is still crewed and I think Dragon-2 de-orbits with excess fuel in case of an emergency powered landing.
Could I interest you in some clean burning sub-cooled propalox and propalox accessories?
Forget drinking ethanol meant for rocket fuel, propÆne is the eutectic fuel mixture you can huff!

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