Author Topic: SpaceX Dragon XL  (Read 321708 times)

Offline cohberg

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Re: SpaceX Dragon XL
« Reply #640 on: 11/30/2021 03:11 pm »
I do not think that the DeltaV issue is quite as bad as you might think.

A single core F9 (the "crew certified solution") does not have enough performance to get a crew dragon there.

SpaceX already needs to expend all three cores on a F9 Heavy to do fast transit for DragonXL.
Fast transit is needed because there are people using consumables (who would want to spend 240+ days total in a Dragon).

After using all ~420m/s of delta-v to get to NHRO on a expendable (non crew rated) F9H, Crew Dragon wouldn't have 450m/s of delta-v left to get back from NHRO to LEO / land (even more delta-v).
« Last Edit: 11/30/2021 03:28 pm by cohberg »

Offline spacenut

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Re: SpaceX Dragon XL
« Reply #641 on: 11/30/2021 03:58 pm »
What if Crew Dragon had an engine and small fuel tanks in the trunk of the service module?  Should be enough to get it back to earth.  I think this is what people are talking about.  The trunk is basically empty.  Probably only one Super Draco would be needed to break free of the Gateway orbit at apogee, and get in a free return to earth.  The Dragon II capsule is not as heavy as Orion, probably half as heavy. 
« Last Edit: 11/30/2021 04:02 pm by spacenut »

Offline whitelancer64

Re: SpaceX Dragon XL
« Reply #642 on: 11/30/2021 04:13 pm »
There are multiple other threads on NSF covering how to make Crew Dragon into a vehicle that could go to the Moon and back. Including trunk modifications.
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Offline cohberg

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Re: SpaceX Dragon XL
« Reply #643 on: 11/30/2021 04:56 pm »
All this crew dragon stuff should be moved to another thread. As already stated, D2 was designed for LEO and was always just a stepping stone to bigger and better things.

Maybe add some Superdracos in the trunk with some hypergolic fuel for return to earth. 

Crew Dragon has an empty trunk.  Why not use it for Super Dracos and some hypergolic fuel for the return flight.

What if Crew Dragon had an engine and small fuel tanks in the trunk of the service module?

You can't "just add engines and propellant" in the trunk:

* Crew dragon 2 trunks are different from cargo dragon trunks: no cargo rack on crew (needed for engines, tanks), no drag rack on cargo (needed for aborts). They occupy the same mounting points on the trunk.
* Your abort performance is greatly hindered.
* CoM changes (vs an empty trunk) when aborting.
* F9H fully expended can already barely put a lighter Dragon XL into NHRO (with no return capability). You want to make the already heavier D2 even heavier?
* SuperDraco's are underexpanded for vacuum. You'd need a new vacuum nozzle to close the gap from 235s to 300s+ for a regular Draco to get any semblance of efficiency
* How you you control it? Spend more fuel thrusting away with Dracos to keep it pointed in the right direction? Spend more weight, time, money on thrust vectoring for SuperDraco?
* Countless other reasons



« Last Edit: 12/03/2021 02:25 pm by cohberg »

Offline whitelancer64

Re: SpaceX Dragon XL
« Reply #644 on: 11/30/2021 07:08 pm »
Don't know if this is the right place to ask this question, so please redirect if needed.

I assume its feasible to send a Crew Dragon to the Gateway. Would it have to be with a FH or F9?

<snip> I suspect you also need a new heat shield. At this point you have just re-invented Orion.  Why bother? just send a crewed Starship.</snip>

Dragon does not need a new heatshield. The current heatshield is already rated for lunar and Mars reentry into Earth's atmosphere.

According to SpaceX; PICA-X, which is SpaceX's proprietary derivative of the PICA (Phenolic Impregnated Carbon Ablator) heatshield designed by NASA, can withstand reentries from "Lunar and Martian Velocities". Martian velocities being even higher, of course.

PICA itself was used on the Stardust spacecraft which reentered at a speed of 46,500km/h. Apollo craft generally reentered at a speed of ~40,000km/h. An Earth reentry from Mars would, depending on how much energy you choose to expend, be between 49,000km/h-77,000km/h. Wired article.

Another source is testimony that Garret Reisman himself offered, on page 4, where he says: Designed in partnership with NASA and fabricated by SpaceX, Crew Dragon’s heat shield is made of PICA-X, a high-performance improvement on NASA’s original phenolic impregnated carbon ablator (PICA). PICA-X is designed to withstand heat rates from a lunar return mission, which far exceed the requirements for a low Earth orbit mission.

Any ablative material can be made thick enough to withstand reentry from lunar / Mars return velocities. PICA-X isn't special in that regard, it has nothing to do with the material itself.

Note: that prepared statement is from early 2015, at the time the Crew Dragon was not quite yet in a fully mature state of design. Propulsive landing was still in play at that point, and it still had the movable ballast sled, both of which were discussed in the statement.

A much more recent statement from Garret Reismann for a 2020 arstechnica article says that the heatshield would require some modification (i.e., being made thicker) to handle a lunar return.

"Crew Dragon was designed for low Earth orbit ... traveling beyond low Earth orbit would therefore require some substantial but feasible changes to the spacecraft, Reismann said. Dragon’s communication system works through GPS, so it would need a new communications and navigation system. In terms of radiation, he said, addressing this for astronauts is relatively straightforward, but hardening electronics would require some work. The heat shield could be made capable of returning from the Moon relatively easily, Reismann said. Additional consumables for a longer journey would take up interior volume."

https://arstechnica.com/science/2020/08/could-a-dragon-spacecraft-fly-humans-to-the-moon-its-complicated/
« Last Edit: 11/30/2021 07:09 pm by whitelancer64 »
"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 deadman1204

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Re: SpaceX Dragon XL
« Reply #645 on: 12/03/2021 12:48 am »
Don't know if this is the right place to ask this question, so please redirect if needed.

I assume its feasible to send a Crew Dragon to the Gateway. Would it have to be with a FH or F9?

<snip> I suspect you also need a new heat shield. At this point you have just re-invented Orion.  Why bother? just send a crewed Starship.</snip>

Dragon does not need a new heatshield. The current heatshield is already rated for lunar and Mars reentry into Earth's atmosphere.

According to SpaceX; PICA-X, which is SpaceX's proprietary derivative of the PICA (Phenolic Impregnated Carbon Ablator) heatshield designed by NASA, can withstand reentries from "Lunar and Martian Velocities". Martian velocities being even higher, of course.

PICA itself was used on the Stardust spacecraft which reentered at a speed of 46,500km/h. Apollo craft generally reentered at a speed of ~40,000km/h. An Earth reentry from Mars would, depending on how much energy you choose to expend, be between 49,000km/h-77,000km/h. Wired article.

Another source is testimony that Garret Reisman himself offered, on page 4, where he says: Designed in partnership with NASA and fabricated by SpaceX, Crew Dragon’s heat shield is made of PICA-X, a high-performance improvement on NASA’s original phenolic impregnated carbon ablator (PICA). PICA-X is designed to withstand heat rates from a lunar return mission, which far exceed the requirements for a low Earth orbit mission.

Any ablative material can be made thick enough to withstand reentry from lunar / Mars return velocities. PICA-X isn't special in that regard, it has nothing to do with the material itself.

Note: that prepared statement is from early 2015, at the time the Crew Dragon was not quite yet in a fully mature state of design. Propulsive landing was still in play at that point, and it still had the movable ballast sled, both of which were discussed in the statement.

A much more recent statement from Garret Reismann for a 2020 arstechnica article says that the heatshield would require some modification (i.e., being made thicker) to handle a lunar return.

"Crew Dragon was designed for low Earth orbit ... traveling beyond low Earth orbit would therefore require some substantial but feasible changes to the spacecraft, Reismann said. Dragon’s communication system works through GPS, so it would need a new communications and navigation system. In terms of radiation, he said, addressing this for astronauts is relatively straightforward, but hardening electronics would require some work. The heat shield could be made capable of returning from the Moon relatively easily, Reismann said. Additional consumables for a longer journey would take up interior volume."

https://arstechnica.com/science/2020/08/could-a-dragon-spacecraft-fly-humans-to-the-moon-its-complicated/
It doesn't matter. This thread is about dragon XL, not crew dragon.

Offline baldusi

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Re: SpaceX Dragon XL
« Reply #646 on: 12/05/2021 03:07 am »
And lets remember that Deep space environment is different: thermal, radiation and comms are completely different. Reliability requirements are much higher. And abort cases a lot more complicated. All these have been discused ad nauseam here. Yes, much of that technology will be developed for Dragon XL. But crew adds another huge layer of extra requirements and would be quite a new development. So, please go to one of the many threads discussing the issue.

Offline wannamoonbase

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Re: SpaceX Dragon XL
« Reply #647 on: 03/08/2022 03:47 pm »
With all of the projects that SpaceX has going on this one seems to produce zero news.

Is it a low level project at this point or is SpaceX just keeping it quiet.

I would expect some information through NASA reporting and design requirements.

Thanks for humoring me.
When do we see the first Superheavy reuse?

Offline yg1968

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Re: SpaceX Dragon XL
« Reply #648 on: 03/08/2022 04:07 pm »
With all of the projects that SpaceX has going on this one seems to produce zero news.

Is it a low level project at this point or is SpaceX just keeping it quiet.

I would expect some information through NASA reporting and design requirements.

Thanks for humoring me.

The Gateway Logistics Services (GLS) contract is backloaded, most of the payments will only start being made in 2024 and 2025 (see the attached IG chart).

You can also get updates on the GLS contract from these websites:
https://www.usaspending.gov/award/CONT_AWD_80KSC020C0012_8000_-NONE-_-NONE-
https://govtribe.com/award/federal-contract-award/definitive-contract-80ksc020c0012
« Last Edit: 03/08/2022 04:11 pm by yg1968 »

Online DanClemmensen

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Re: SpaceX Dragon XL
« Reply #649 on: 03/08/2022 04:14 pm »
With all of the projects that SpaceX has going on this one seems to produce zero news.

Is it a low level project at this point or is SpaceX just keeping it quiet.

I would expect some information through NASA reporting and design requirements.

Thanks for humoring me.
We don't seem to be hearing much about Lunar Gateway at all, much less Dragon XL. Gateway is now considered optional for Artemis III and will not even get its third module, I-HAB,  until Artemis IV. I don't know when it will need its first Dragon XL supply mission, but I think it must surely be after 2026.

Speculation: although Starship HLS is not intended for Gateway logistics, It is probably capable of it, and a variant would clearly be capable of it. It would be less expensive per mission even if non-reusable, with of course massively increased capacity. The smart thing to do would be cancel Dragon XL in favor of Starship GLS. The smarter thing to do would be cancel Gateway.

Offline wannamoonbase

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Re: SpaceX Dragon XL
« Reply #650 on: 03/08/2022 04:29 pm »
With all of the projects that SpaceX has going on this one seems to produce zero news.

Is it a low level project at this point or is SpaceX just keeping it quiet.

I would expect some information through NASA reporting and design requirements.

Thanks for humoring me.
We don't seem to be hearing much about Lunar Gateway at all, much less Dragon XL. Gateway is now considered optional for Artemis III and will not even get its third module, I-HAB,  until Artemis IV. I don't know when it will need its first Dragon XL supply mission, but I think it must surely be after 2026.

Speculation: although Starship HLS is not intended for Gateway logistics, It is probably capable of it, and a variant would clearly be capable of it. It would be less expensive per mission even if non-reusable, with of course massively increased capacity. The smart thing to do would be cancel Dragon XL in favor of Starship GLS. The smarter thing to do would be cancel Gateway.


Dumping Gateway wouldn't upset me.

Thanks for the update and discussion on this interesting vehicle.
« Last Edit: 03/08/2022 04:30 pm by wannamoonbase »
When do we see the first Superheavy reuse?

Offline whitelancer64

Re: SpaceX Dragon XL
« Reply #651 on: 03/08/2022 04:56 pm »
With all of the projects that SpaceX has going on this one seems to produce zero news.

Is it a low level project at this point or is SpaceX just keeping it quiet.

I would expect some information through NASA reporting and design requirements.

Thanks for humoring me.

As of nearly a year ago, NASA had not yet given SpaceX authorization to proceed. There had been some contract modifications related to development work for it. More details here:

https://spacenews.com/nasa-delays-starting-contract-with-spacex-for-gateway-cargo-services/

The first DragonXL wouldn't need to launch until 2026 at the earliest, and probably more like 2027, to deliver supplies and equipment to the Gateway for the Artemis 4 mission, which, as of now, is only to install the iHab and outfit the Gateway for the first time.
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Offline butters

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Re: SpaceX Dragon XL
« Reply #652 on: 03/08/2022 06:01 pm »
Two years ago this month, I opined in this thread that hopefully SpaceX won't actually have to build Dragon XL, if NASA uses Starship as part of Artemis, they'll inevitably harmonize their roadmap with SpaceX, and Dragon XL will fall by the wayside. Subsequently, NASA admitted that maximum mass limit in the Gateway Logistics requirements, which excluded the possibility of bidding Starship, was unnecessary in hindsight. This was a botched procurement, and neither party wants to sink any money into it. NASA isn't going to need this. Commercial customers aren't going to need this. Nobody is going to need this, and there's no reason to build it.

Offline Tomness

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Re: SpaceX Dragon XL
« Reply #653 on: 03/08/2022 06:03 pm »
Two years ago this month, I opined in this thread that hopefully SpaceX won't actually have to build Dragon XL, if NASA uses Starship as part of Artemis, they'll inevitably harmonize their roadmap with SpaceX, and Dragon XL will fall by the wayside. Subsequently, NASA admitted that maximum mass limit in the Gateway Logistics requirements, which excluded the possibility of bidding Starship, was unnecessary in hindsight. This was a botched procurement, and neither party wants to sink any money into it. NASA isn't going to need this. Commercial customers aren't going to need this. Nobody is going to need this, and there's no reason to build it.

Axiom could use it out fit their station.

Offline butters

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Re: SpaceX Dragon XL
« Reply #654 on: 03/08/2022 06:07 pm »
Two years ago this month, I opined in this thread that hopefully SpaceX won't actually have to build Dragon XL, if NASA uses Starship as part of Artemis, they'll inevitably harmonize their roadmap with SpaceX, and Dragon XL will fall by the wayside. Subsequently, NASA admitted that maximum mass limit in the Gateway Logistics requirements, which excluded the possibility of bidding Starship, was unnecessary in hindsight. This was a botched procurement, and neither party wants to sink any money into it. NASA isn't going to need this. Commercial customers aren't going to need this. Nobody is going to need this, and there's no reason to build it.

Axiom could use it out fit their station.
It's expendable and requires FH and would therefore be $$$ compared to standard Cargo Dragon 2.

Offline Tomness

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Re: SpaceX Dragon XL
« Reply #655 on: 03/08/2022 06:24 pm »
Two years ago this month, I opined in this thread that hopefully SpaceX won't actually have to build Dragon XL, if NASA uses Starship as part of Artemis, they'll inevitably harmonize their roadmap with SpaceX, and Dragon XL will fall by the wayside. Subsequently, NASA admitted that maximum mass limit in the Gateway Logistics requirements, which excluded the possibility of bidding Starship, was unnecessary in hindsight. This was a botched procurement, and neither party wants to sink any money into it. NASA isn't going to need this. Commercial customers aren't going to need this. Nobody is going to need this, and there's no reason to build it.

Axiom could use it out fit their station.
It's expendable and requires FH and would therefore be $$$ compared to standard Cargo Dragon 2.

Doesn't have to be, retrieve it like ULA going to retrieve their BE-4 via S.M.A.R.T.

Offline yg1968

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Re: SpaceX Dragon XL
« Reply #656 on: 03/08/2022 06:30 pm »
Quote from: pages 5 and 6 of the MOU
Article 5. Gateway Elements

5.5 The Gateway is comprised of the following elements, although the Parties recognize these are subject to change in the course of the detailed design, development, and operation of the Gateway. The Parties intend for an up-to-date listing of all of the Gateway's elements to be maintained in accordance with Article 8 (Management).

(a) NASA:
1. Power and Propulsion
2. Habitation Capability
3. Avionics and Communications Infrastructure
4. Logistics Resupply
5. Crew Transportation
6. Extravehicular Activity (EVA) System

(b) CSA:
1. External Robotic Capability
2. External Robotics Interfaces
3. End-to-End External Robotic Operations

(c) ESA:
1. Habitation Capability (I-Hab)
2. Enhanced Lunar Communications
3. Refueling and Viewing Capability
4. European Service Modules in support of Orion missions

(d) The GOJ [Japan]:
1. Habitation Capability Infrastructure Functions
2. Logistics Resupply

(e) ROSCOSMOS:
1. Crew Airlock


Article 6. Major Program Milestones

6.1 Major target milestones are as follows:

(a) 2023 — Delivery of the first Gateway element, power and propulsion, to lunar orbit
(b) 2023 — Delivery of the initial habitation capability with enhanced lunar communications to the Gateway
(c) 2024 — Gateway ready for the first crewed mission
(d) 2025 — Delivery of additional habitation capability to the Gateway (I-Hab)
(e) 2026 — Delivery of external robotic capability to the Gateway
(f) 2027 — Delivery of refueling and viewing element to the Gateway
(g) 2028 — Delivery of the crew airlock to the Gateway

https://t.co/gsyzWQBwr2?amp=1

See the timeline above. You can essentially add a year to all of these dates. I think that the first Dragon XL and the I-Hab are part of the Artemis IV mission. The second Dragon XL would be used to bring the external robotic capability to Gateway. 

Offline KSC Sage

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Re: SpaceX Dragon XL
« Reply #657 on: 03/08/2022 06:37 pm »
Quote from: pages 5 and 6 of the MOU
Article 5. Gateway Elements

5.5 The Gateway is comprised of the following elements, although the Parties recognize these are subject to change in the course of the detailed design, development, and operation of the Gateway. The Parties intend for an up-to-date listing of all of the Gateway's elements to be maintained in accordance with Article 8 (Management).

(a) NASA:
1. Power and Propulsion
2. Habitation Capability
3. Avionics and Communications Infrastructure
4. Logistics Resupply
5. Crew Transportation
6. Extravehicular Activity (EVA) System

(b) CSA:
1. External Robotic Capability
2. External Robotics Interfaces
3. End-to-End External Robotic Operations

(c) ESA:
1. Habitation Capability (I-Hab)
2. Enhanced Lunar Communications
3. Refueling and Viewing Capability
4. European Service Modules in support of Orion missions

(d) The GOJ [Japan]:
1. Habitation Capability Infrastructure Functions
2. Logistics Resupply

(e) ROSCOSMOS:
1. Crew Airlock


Article 6. Major Program Milestones

6.1 Major target milestones are as follows:

(a) 2023 — Delivery of the first Gateway element, power and propulsion, to lunar orbit
(b) 2023 — Delivery of the initial habitation capability with enhanced lunar communications to the Gateway
(c) 2024 — Gateway ready for the first crewed mission
(d) 2025 — Delivery of additional habitation capability to the Gateway (I-Hab)
(e) 2026 — Delivery of external robotic capability to the Gateway
(f) 2027 — Delivery of refueling and viewing element to the Gateway
(g) 2028 — Delivery of the crew airlock to the Gateway

https://t.co/gsyzWQBwr2?amp=1

See the timeline above. You can essentially add a year to all of these dates. I think that the first Dragon XL and the I-Hab are part of the Artemis IV mission. The second Dragon XL would be used to bring the external robotic capability to Gateway. 
Right now, Artemis IV is NET Summer of 2026.

Offline clongton

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Re: SpaceX Dragon XL
« Reply #658 on: 03/08/2022 10:46 pm »
The smart thing to do would be cancel Dragon XL in favor of Starship GLS. The smarter thing to do would be cancel Gateway.

Unwise. I wouldn't even consider considering Starship until it flies to at least LEO and successfully returns to the launch site - several times. Once it has consistently demonstrated that it will actually live up to all the hype, then maybe. All of us have the highest expectations for Starship but as of now it is not a viable option. It has only made low level hops using engines that will not even be on the operational vehicle and the booster has never flown at all. Don't let your enthusiasm get ahead of reality.
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Online DanClemmensen

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Re: SpaceX Dragon XL
« Reply #659 on: 03/09/2022 12:11 am »
The smart thing to do would be cancel Dragon XL in favor of Starship GLS. The smarter thing to do would be cancel Gateway.

Unwise. I wouldn't even consider considering Starship until it flies to at least LEO and successfully returns to the launch site - several times. Once it has consistently demonstrated that it will actually live up to all the hype, then maybe. All of us have the highest expectations for Starship but as of now it is not a viable option. It has only made low level hops using engines that will not even be on the operational vehicle and the booster has never flown at all. Don't let your enthusiasm get ahead of reality.
Apparently the first GLS mission is in NET 2026. The first Starship HLS mission is in 2024, and Artemis 3 depends on Starship HLS. Thus, Artemis is already dependent on the success of Starship and depending on another simpler variant does not appreciably increase the risk to the Artemis program.  As I said in the portion of my post that you trimmed, this GLS variant can be expendable, like HLS, and a Starship GLS mission would still be cheaper than a Dragon XL mission.

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