Author Topic: Gateway Discussion Thread  (Read 49064 times)

Offline Khadgars

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Re: Gateway Discussion Thread
« Reply #220 on: 07/30/2022 03:26 pm »
Exactly!
It won't be necessary at all!
There is nothing between earth, moon and mars what a Starship couldn't do better than any Gateway (or spaceship!)

I like Starship but to think it will replace everything between earth, moon and Mars is ridiculous. 
Evil triumphs when good men do nothing - Thomas Jefferson

Offline DanClemmensen

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Re: Gateway Discussion Thread
« Reply #221 on: 07/30/2022 03:54 pm »
Exactly!
It won't be necessary at all!
There is nothing between earth, moon and mars what a Starship couldn't do better than any Gateway (or spaceship!)

I like Starship but to think it will replace everything between earth, moon and Mars is ridiculous.
Starship will only replace other spacecraft that are very clearly less capable of performing the function in which Starship is replacing them. Timing is important: if a non-Starship spacecraft is already designed and is being produced in time for a mission but the appropriate Starship is not, then clearly Starship cannot replace it. The opposite is also true.

To show that "replace everything" is ridiculous, all you need to do is identify a mission that another spacecraft can accomplish but that Starship cannot do better, taking schedule into account.

Offline su27k

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Re: Gateway Discussion Thread
« Reply #222 on: 07/31/2022 02:11 am »
Exactly!
It won't be necessary at all!
There is nothing between earth, moon and mars what a Starship couldn't do better than any Gateway (or spaceship!)

I like Starship but to think it will replace everything between earth, moon and Mars is ridiculous.

He didn't say it'll replace everything, he said it'll be better than Gateway and - presumably - any Gateway derived spacecraft, which I think it's correct.

Offline Coastal Ron

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Re: Gateway Discussion Thread
« Reply #223 on: 07/31/2022 03:09 am »
The Artemis Gateway is a political animal, and things created for political reasons tend to be compromises and NOT durable solutions.

Remember the goal of the Artemis program is to "...land the first woman and first person of color on the Moon, using innovative technologies to explore more of the lunar surface than ever before."

The Gateway is supposed to support that goal, though it is hobbled by the transportation system the Artemis program uses to transport crew to the Moon (i.e. the SLS+Orion) - $1B per person, and it is only currently funded to go there once a year for a few weeks. Not only that, but the limitations of the SLS+Orion force the Gateway to be in a ~7 day polar near-rectilinear halo orbit (NRHO), which means the Gateway takes longer to circle the Moon than it takes to fly the crew from Earth to the Moon, AND back. Not optimal for safety reasons.

However political programs are measured by different criteria than commercial or non-profit ones, and usually money is not a primary consideration. We know this to be true for the SLS and Orion programs.

But unlike the SLS and Orion programs, the Gateway is being built as an international partnership, which means it has different goals than the SLS and Orion programs. That also means that if there is an alternative to the SLS and Orion for transporting crew to/from the Gateway, that could be added on top of the existing SLS and Orion flights.

In other words, I think there is a possibility for a parallel transportation to be incorporated into the Artemis program that would be in addition to the SLS+Orion, especially if the Artemis partners advocate for that.

And why might the Artemis partners advocate for that? Because it could mean that they would get more use out of their investment - more missions, and maybe for not much more cost.

I wonder if, in a future where the SLS+Orion are replaces by something with more capabilities, if the Gateway could be moved into a closer orbit to the Moon? Besides the cost of the energy to do that, any technical reasons why it couldn't? Just a thought...
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline Eric Hedman

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Re: Gateway Discussion Thread
« Reply #224 on: 07/31/2022 05:28 am »
I wonder if, in a future where the SLS+Orion are replaces by something with more capabilities, if the Gateway could be moved into a closer orbit to the Moon? Besides the cost of the energy to do that, any technical reasons why it couldn't? Just a thought...
There is no technical reason that I am aware of that it couldn't be moved.  Before the Gateway got funded for full development, there was plenty of discussion that it could move between, NRHO, LLO, L1 and L2 to wherever it would be needed at the time.  I don't think anything has changed that would prevent that.
« Last Edit: 07/31/2022 05:31 am by Eric Hedman »

Offline DanClemmensen

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Re: Gateway Discussion Thread
« Reply #225 on: 07/31/2022 01:58 pm »

I wonder if, in a future where the SLS+Orion are replaces by something with more capabilities, if the Gateway could be moved into a closer orbit to the Moon? Besides the cost of the energy to do that, any technical reasons why it couldn't? Just a thought...
Apparently, the PPE (Power and Propulsion Element) is specifically designed to move stuff around with high efficiency, using ion engines. It will need to be refuelled, but presumably Dragon XL can do this. This assumes gateway as it evolves is designed to be accellerated by PPE. We know the initial gateway (PPE+HALO) is designed to be accelerated by PPE.

Offline Zed_Noir

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Re: Gateway Discussion Thread
« Reply #226 on: 07/31/2022 04:42 pm »
Responding to query from the update thread

https://www.gao.gov/assets/gao-22-105212.pdf

Quote from: Page 51
As of February 2022, the co-manifested vehicle is above the Falcon
Heavy launch vehicle’s mass limit. If the mass is too high, it could affect
the vehicle’s ability to reach the correct lunar orbit. The project is taking
steps to reduce mass, including evaluating whether it needs to
potentially off-load some components for initial launch.
co-manifested vehicle = PPE + HALO
I don't understand this quote. Falcon Heavy was never supposed to put PPE+HALO into a lunar orbit in the first place. As I uderstand it, after FH puts PPE+HALO into orbit, PPE is supposed to move PPE+HALO into NRHO, taking about nine months to do so. If PPE+HALO is heavier, PPE will have more work to do. Worst case, PPE will need refuelling, but it is supposed to be designed for this, presumably from Dragon XL as part of GLS.

Guessing it might be the maximum mass the payload adapter on the Falcon upper stage is rated for. The integrated PPE & HALO stack is a lot of mass on top of a launcher going to LEO.

Offline DanClemmensen

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Re: Gateway Discussion Thread
« Reply #227 on: 07/31/2022 04:59 pm »
Responding to query from the update thread

https://www.gao.gov/assets/gao-22-105212.pdf

Quote from: Page 51
As of February 2022, the co-manifested vehicle is above the Falcon
Heavy launch vehicle’s mass limit. If the mass is too high, it could affect
the vehicle’s ability to reach the correct lunar orbit. The project is taking
steps to reduce mass, including evaluating whether it needs to
potentially off-load some components for initial launch.
co-manifested vehicle = PPE + HALO
I don't understand this quote. Falcon Heavy was never supposed to put PPE+HALO into a lunar orbit in the first place. As I uderstand it, after FH puts PPE+HALO into orbit, PPE is supposed to move PPE+HALO into NRHO, taking about nine months to do so. If PPE+HALO is heavier, PPE will have more work to do. Worst case, PPE will need refuelling, but it is supposed to be designed for this, presumably from Dragon XL as part of GLS.

Guessing it might be the maximum mass the payload adapter on the Falcon upper stage is rated for. The integrated PPE & HALO stack is a lot of mass on top of a launcher going to LEO.
OK, but the quote does not say it cannot get to LEO. It says "it could affect the vehicle’s ability to reach the correct lunar orbit." Sure, failure to reach orbit at all would have that effect, but that's like saying that a fatal heart attack might affect your circulation.

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Re: Gateway Discussion Thread
« Reply #228 on: 07/31/2022 10:14 pm »
PPE [...] will need to be refuelled, but presumably Dragon XL can do this.

Isn't refilling the PPE with propellant the job of ESPRIT?

Quote
A second contribution called Esprit, will supply enhanced communications, refuelling and a window
https://www.esa.int/ESA_Multimedia/Images/2020/10/What_is_Esprit
— 𝐬𝐝𝐒𝐝𝐬 —

Offline Jim

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Re: Gateway Discussion Thread
« Reply #229 on: 07/31/2022 11:15 pm »

Guessing it might be the maximum mass the payload adapter on the Falcon upper stage is rated for. The integrated PPE & HALO stack is a lot of mass on top of a launcher going to LEO.


That isn't an issue

Offline DanClemmensen

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Re: Gateway Discussion Thread
« Reply #230 on: 07/31/2022 11:31 pm »
PPE [...] will need to be refuelled, but presumably Dragon XL can do this.

Isn't refilling the PPE with propellant the job of ESPRIT?

Quote
A second contribution called Esprit, will supply enhanced communications, refuelling and a window
https://www.esa.int/ESA_Multimedia/Images/2020/10/What_is_Esprit
Apparently EPSRIT will become a permanent part of the Gateway. Among other functions it houses extra fuel tanks for PPE, but it does not actually bring refills.
   https://en.wikipedia.org/wiki/European_System_Providing_Refueling,_Infrastructure_and_Telecommunications#/media/File:Gateway-configuration-20180705.jpg

     

Offline DanClemmensen

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Re: Gateway Discussion Thread
« Reply #231 on: 08/01/2022 04:20 pm »
https://www.gao.gov/assets/gao-22-105212.pdf

Quote from: Page 51
As of February 2022, the co-manifested vehicle is above the Falcon
Heavy launch vehicle’s mass limit. If the mass is too high, it could affect
the vehicle’s ability to reach the correct lunar orbit. The project is taking
steps to reduce mass, including evaluating whether it needs to
potentially off-load some components for initial launch.
co-manifested vehicle = PPE + HALO
I don't understand this quote. Falcon Heavy was never supposed to put PPE+HALO into a lunar orbit in the first place. As I uderstand it, after FH puts PPE+HALO into orbit, PPE is supposed to move PPE+HALO into NRHO, taking about nine months to do so. If PPE+HALO is heavier, PPE will have more work to do. Worst case, PPE will need refuelling, but it is supposed to be designed for this, presumably from Dragon XL as part of GLS.

If PPE+HALO is sufficiently overweight, then the Falcon Heavy might not be able to put it into its target high Earth orbit insertion. The PPE might not have enough fuel to break out of Earth orbit and insert the modules into the NRHO orbit.

Refueling would add complexity (another launch, the refueling vehicle) to the mission, and aside from increasing the cost, would delay it until the refueling vehicle was ready.
The other alternative would be to switch back to the concept of launching PPE and HALO separately and mating them in space. That was part of mpst of the early concepts, I think. The pre-mated, single-launch PPE+HALO is relatively recent. I don't know if two FH launches could put HALO and PPE into NRHO separately, but surely they could be assembled in a high Earth orbit before having PPE take them to NRHO? This would require autonomous or tele-operated assembly, or doing the assembly in an orbit that is reachable by Crew Dragon, which might not be high enough.

Offline DanClemmensen

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Re: Gateway Discussion Thread
« Reply #232 on: 08/01/2022 04:26 pm »
I have become very confused (or I have become aware that I am very confused).

The Gateway architecture has changed quite a lot over multiple iterations, so quite a few diagrams or graphics about the layout are obsolete and quite a few older published statements about Gateway are no longer valid.

Is there a definitive current architecture published somewhere? Where?

Is there any sort of coherent description of the evolution of the architecture? Where?

Offline DanClemmensen

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Re: Gateway Discussion Thread
« Reply #233 on: 08/01/2022 04:36 pm »
How will the PPE be refuelled? One of the several pieces that make up ESPRIT is (was?) called a refuelling module, but it appears (appeared?) to be permanently attached to Gateway, and it has an extra dock and other permanent stuff, and no apparent way to maneuver, so it does not appear to be intended to be replaced. The only current GLS (Gateway logistics services) spacecraft is Dragon XL, and I see no mention that it will be carrying PPE fuel. PPE can use Xenon for its electric thrusters and can also(?) use "chemical propulsion(?)" and the ERM has tankage for both.
« Last Edit: 08/01/2022 05:17 pm by DanClemmensen »

Offline Jim

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Re: Gateway Discussion Thread
« Reply #234 on: 08/01/2022 05:46 pm »
The other alternative would be to switch back to the concept of launching PPE and HALO separately and mating them in space.

Not happening

Offline whitelancer64

Re: Gateway Discussion Thread
« Reply #235 on: 08/01/2022 05:48 pm »
How will the PPE be refuelled? One of the several pieces that make up ESPRIT is (was?) called a refuelling module, but it appears (appeared?) to be permanently attached to Gateway, and it has an extra dock and other permanent stuff, and no apparent way to maneuver, so it does not appear to be intended to be replaced. The only current GLS (Gateway logistics services) spacecraft is Dragon XL, and I see no mention that it will be carrying PPE fuel. PPE can use Xenon for its electric thrusters and can also(?) use "chemical propulsion(?)" and the ERM has tankage for both.

ESPIRIT is currently intended to dock to one of the side ports on the HALO module. Its design is doughnut-shaped, with a transfer tunnel in the center and docking ports on both sides, so that logistics vehicles can dock to it and still deliver supplies to the Gateway.

Logistics / resupply vehicles are supposed to be able to transfer more Xenon and bipropellant fuel to the ESPIRIT module, yes. I suppose that a logistics vehicle would technically be able to supply the fuel directly, without ESPIRIT as an intermediate.

Attached document, "JOINT DEVELOPMENT TESTING OF THE INTEGRATED GATEWAY-ESPRIT BIPROPELLANT REFUELLING SYSTEM" with screenshots from it, is from May 2022

Anatoly Zak's render is slightly dated - Roscosmos is no longer providing an airlock - but does show ESPIRIT in the correct position.
« Last Edit: 08/01/2022 06:01 pm by whitelancer64 »
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Offline whitelancer64

Re: Gateway Discussion Thread
« Reply #236 on: 08/01/2022 05:59 pm »
https://www.gao.gov/assets/gao-22-105212.pdf

Quote from: Page 51
As of February 2022, the co-manifested vehicle is above the Falcon
Heavy launch vehicle’s mass limit. If the mass is too high, it could affect
the vehicle’s ability to reach the correct lunar orbit. The project is taking
steps to reduce mass, including evaluating whether it needs to
potentially off-load some components for initial launch.
co-manifested vehicle = PPE + HALO
I don't understand this quote. Falcon Heavy was never supposed to put PPE+HALO into a lunar orbit in the first place. As I uderstand it, after FH puts PPE+HALO into orbit, PPE is supposed to move PPE+HALO into NRHO, taking about nine months to do so. If PPE+HALO is heavier, PPE will have more work to do. Worst case, PPE will need refuelling, but it is supposed to be designed for this, presumably from Dragon XL as part of GLS.

If PPE+HALO is sufficiently overweight, then the Falcon Heavy might not be able to put it into its target high Earth orbit insertion. The PPE might not have enough fuel to break out of Earth orbit and insert the modules into the NRHO orbit.

Refueling would add complexity (another launch, the refueling vehicle) to the mission, and aside from increasing the cost, would delay it until the refueling vehicle was ready.
The other alternative would be to switch back to the concept of launching PPE and HALO separately and mating them in space. That was part of mpst of the early concepts, I think. The pre-mated, single-launch PPE+HALO is relatively recent. I don't know if two FH launches could put HALO and PPE into NRHO separately, but surely they could be assembled in a high Earth orbit before having PPE take them to NRHO? This would require autonomous or tele-operated assembly, or doing the assembly in an orbit that is reachable by Crew Dragon, which might not be high enough.

RCS maneuvering systems, independent solar panels, star trackers for orientation, etc. have already been removed from the HALO design. It is not capable of free flight.

Reminder that production and assembly for both modules is already well underway. Going back to a separate launch for each one would involve a pretty hard reset of the entire Gateway program, with significant redesign and rework required. Gateway would be delayed for a couple of years at least.
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
"There are lies, damned lies, and launch schedules." - Larry J

Offline whitelancer64

Re: Gateway Discussion Thread
« Reply #237 on: 08/01/2022 06:05 pm »
I have become very confused (or I have become aware that I am very confused).

The Gateway architecture has changed quite a lot over multiple iterations, so quite a few diagrams or graphics about the layout are obsolete and quite a few older published statements about Gateway are no longer valid.

Is there a definitive current architecture published somewhere? Where?

Is there any sort of coherent description of the evolution of the architecture? Where?

The image on this tweet is also a good visual for the currently planned design.
https://twitter.com/NASA_Gateway/status/1516824035140677634
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
"There are lies, damned lies, and launch schedules." - Larry J

Online butters

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Re: Gateway Discussion Thread
« Reply #238 on: 08/01/2022 06:34 pm »
Oh I see. ESPIRIT was previously supposed to be attached to the PPE as the second module of the Gateway. But since the HALO was subsequently co-manifested with the PPE, most of ESPIRIT moved to its current location where the logistics module was supposed to dock to HALO, requiring ESPIRIT to be redesigned in a donut shape and also requiring the HALO to have plumbing running through it for PPE refueling. Meanwhile, ESPIRIT's communications system was added to the PPE+HALO party by virtue of being necessary for the Minimal Gateway.

It all makes sense. For some definition of sense-making that comes from following the human exploration saga for long enough. The current design is weird because the original design would have taken almost literally forever to assemble as envisioned for extremely familiar reasons. It's shaped like a donut, transfers propellant through the habitation module, and won't be launched for several years after the PPE, because orange rocket bad.
« Last Edit: 08/01/2022 06:34 pm by butters »

Offline DanClemmensen

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Re: Gateway Discussion Thread
« Reply #239 on: 08/01/2022 06:55 pm »
https://www.gao.gov/assets/gao-22-105212.pdf

Quote from: Page 51
As of February 2022, the co-manifested vehicle is above the Falcon
Heavy launch vehicle’s mass limit. If the mass is too high, it could affect
the vehicle’s ability to reach the correct lunar orbit. The project is taking
steps to reduce mass, including evaluating whether it needs to
potentially off-load some components for initial launch.
co-manifested vehicle = PPE + HALO
I don't understand this quote. Falcon Heavy was never supposed to put PPE+HALO into a lunar orbit in the first place. As I uderstand it, after FH puts PPE+HALO into orbit, PPE is supposed to move PPE+HALO into NRHO, taking about nine months to do so. If PPE+HALO is heavier, PPE will have more work to do. Worst case, PPE will need refuelling, but it is supposed to be designed for this, presumably from Dragon XL as part of GLS.

If PPE+HALO is sufficiently overweight, then the Falcon Heavy might not be able to put it into its target high Earth orbit insertion. The PPE might not have enough fuel to break out of Earth orbit and insert the modules into the NRHO orbit.

Refueling would add complexity (another launch, the refueling vehicle) to the mission, and aside from increasing the cost, would delay it until the refueling vehicle was ready.
The other alternative would be to switch back to the concept of launching PPE and HALO separately and mating them in space. That was part of mpst of the early concepts, I think. The pre-mated, single-launch PPE+HALO is relatively recent. I don't know if two FH launches could put HALO and PPE into NRHO separately, but surely they could be assembled in a high Earth orbit before having PPE take them to NRHO? This would require autonomous or tele-operated assembly, or doing the assembly in an orbit that is reachable by Crew Dragon, which might not be high enough.

RCS maneuvering systems, independent solar panels, star trackers for orientation, etc. have already been removed from the HALO design. It is not capable of free flight.

Reminder that production and assembly for both modules is already well underway. Going back to a separate launch for each one would involve a pretty hard reset of the entire Gateway program, with significant redesign and rework required. Gateway would be delayed for a couple of years at least.
OK, PPE and HALO are no longer a pair of "co-manifested" payloads. They are now basically a single spacecraft that has evolved from an earlier pair of modules.

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