Author Topic: SpaceX Dragon XL  (Read 271664 times)

Offline Robotbeat

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Re: SpaceX Dragon XL
« Reply #160 on: 03/28/2020 06:46 pm »
If it is supposed to transfer both pressurized and unpressurized cargo, how could it have docking at both ends?

Also, SpaceX would need to build their own IDSS passive docking port.  Contrary to popular belief, the current system does not have the equipment to act as a passive for other vehicles to dock (ie not androgynous)....
Citation needed. The standard specifies it must be androgynous (at least for active side). If it's not androgynous, it's not IDSS.

For Crew Dragon, androgyny is a safety consideration as well to allow rescue. Doubtful that they'd change the spec for Dragon XL as that'd require more certification.

If you're right, then you should be able to provide a reference. If you're just supposing, then you should say so.

I'm the citation, I work on docking systems.

Also, if you look at any high resolution picture of the SpaceX docking system, there are no passive strikers or hooks, so there is nothing to soft or hard capture to.
Very good, thank you!
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Offline Jimmy Murdok

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Re: SpaceX Dragon XL
« Reply #161 on: 03/28/2020 06:51 pm »
I´ve increased the OD of the white part to 3740mm, so the inner cylinder is the one with 3700. I´ve added 6 x 900liter hydrazine tanks.
Does 3600liters of hydrazine provide a decent DV?
Are the draco thrusters still isp300?
Does this design fregat upperstage style make sense?

Disclaimer: measurements are specultive based on the IDA port and the OD of a F9 stage. Happy to get feedback.
Link to the 3D model:https://cad.onshape.com/documents/d32435cb16f1fe696165b0f7/w/e324511fb848d24897bf37cf/e/b9d1809c586d174ba6e8f9b8

edit: the delta V assuming 10t fully loaded, 6.4 dry is around 1300m/s
« Last Edit: 03/28/2020 08:33 pm by Jimmy Murdok »

Offline butters

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Re: SpaceX Dragon XL
« Reply #162 on: 03/28/2020 07:16 pm »
People are trying to project their hopes and dreams onto this thing, but it's just an expendable Dragon 1 variant with a non-tapered "capsule" to fit more cargo.

This isn't going to have an aft docking adapter. It's not going to be recyclable as a station module. It's not going to launch inside a reusable payload fairing. The only reusability potential in this concept is the FH boosters.

If the Gateway comes to fruition, this is a relatively low-cost design evolution for cargo supply. This isn't something that SpaceX would have wanted on their roadmap, and I doubt they anticipate any commercial market for a vehicle like this, but it would have been poor form for SpaceX not to bid. SpaceX has a strategic interest in playing nice with NASA, and while developing Dragon XL would be a distraction, it's not an overly burdensome detour. NASA will pay enough to make it worthwhile for SpaceX even if they're the only conceivable customer.

Maybe (hopefully?) SpaceX won't ever actually have to build one of these. They'll work through the paper milestones and continue to strengthen their relationship with NASA, because that relationship is what will endure the ever-changing roadmaps for human exploration.
« Last Edit: 03/28/2020 07:17 pm by butters »

Offline Robotbeat

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Re: SpaceX Dragon XL
« Reply #163 on: 03/28/2020 07:24 pm »
People are trying to project their hopes and dreams onto this thing, but it's just an expendable Dragon 1 variant with a non-tapered "capsule" to fit more cargo.

This isn't going to have an aft docking adapter. It's not going to be recyclable as a station module.
MPLM was just a can for cargo until it became a station module when they added some MMOD shielding. ATV is basically a prototype station module, as is Cygnus and Tiangong. Doesn't mean it WILL be used this way, but it can be.
Quote
It's not going to launch inside a reusable payload fairing.
I'd bet money it will. SpaceX will at least attempt fairing recovery on most F9/FH launches from here on out.
« Last Edit: 03/28/2020 07:25 pm by Robotbeat »
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Offline freddo411

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Re: SpaceX Dragon XL
« Reply #164 on: 03/28/2020 07:25 pm »


Maybe (hopefully?) SpaceX won't ever actually have to build one of these. They'll work through the paper milestones and continue to strengthen their relationship with NASA, because that relationship is what will endure the ever-changing roadmaps for human exploration.

I sincerely hope that's not the case.   That sounds suspiciously like so many prior NASA/DOD aerospace projects.   

I believe that type of thinking is one of the key factors in hollowing out a companies spirit and competence.

Competent company culture comes form building and flying hardware; not from collecting contracting money for prototypes that never fly.

FWIW, I think there is a good chance this will fly.

Offline rockets4life97

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Re: SpaceX Dragon XL
« Reply #165 on: 03/28/2020 07:33 pm »
FWIW, I think there is a good chance this will fly.

I feel confident there will at minimum be a demonstration mission. Whatever NASA's plans evolve to in the future, the Dragon XL probably has a role, even if it is only a technology demo with some benefit for Starship development.

Offline butters

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Re: SpaceX Dragon XL
« Reply #166 on: 03/28/2020 07:33 pm »
It's not going to launch inside a reusable payload fairing.
I'd bet money it will. SpaceX will at least attempt fairing recovery on most F9/FH launches from here on out.

They haven't attempted to recover a Dragon 1 nose cap, and that's what Dragon XL is mostly likely to sport. Why would this go inside a fairing? That's just unnecessary mass. The lightweight cork SPAM on the Dragon sidewalls is totally adequate for atmospheric launch.
« Last Edit: 03/28/2020 07:34 pm by butters »

Offline nacnud

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Re: SpaceX Dragon XL
« Reply #167 on: 03/28/2020 07:52 pm »
It's not going to launch inside a reusable payload fairing.
I'd bet money it will. SpaceX will at least attempt fairing recovery on most F9/FH launches from here on out.

They haven't attempted to recover a Dragon 1 nose cap, and that's what Dragon XL is mostly likely to sport. Why would this go inside a fairing? That's just unnecessary mass. The lightweight cork SPAM on the Dragon sidewalls is totally adequate for atmospheric launch.

It launches with the exposed cargo on top, and no solar panel covers or RCS covers. It's going to have a recoverable faring :)

Online TheRadicalModerate

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Re: SpaceX Dragon XL
« Reply #168 on: 03/28/2020 08:23 pm »
It's cargo... Is there some hurry to get it into Lunar orbit in like 3 days?

Even direct transfers to NRHO require 5 days or so.  Ballistic capture transfers require 12-20 weeks, but save 500-600 m/s of delta-v.

The real question here is whether the logistics systems are not only for Gateway support, but whether they're also going to be required to carry propellant for Artemis surface missions before the Gateway exists.  For early Artemis, assuming that Boeing gets its way, you have to launch the lander and ascender so much earlier than the crew (because launching two SLSes in less than 6 months is wildly improbable), that storable prop is the only answer, even if they plan to make the ascender eventually reusable.

There are several ways to evolve from that "expendable lander/ascender in one Block 1B" architecture.  The easiest is simply to refuel and reuse the ascender, but to fit the prop for that into one 5 t logistics flight, the ascender can't be more than 4.5 dry mass and payload, which is almost 2x the mass of the Apollo LM, and therefore is... OK?

One would assume that the main reason to refuel the ascender would be to co-manifest a new lander on a single Orion/Block 1B.  But a storable-based lander would be about 16 t wet, which is about 5 t more than one can co-manifest.

So you could do the following with this HLS architecture:

First mission: 
1) Block 1B cargo takes both the lander and ascender to NRHO.
2) Block 1 takes Orion to NRHO once it's built / stacked / rolled-out (IMO, min 6 months later).
3) Crew transfers to lander/ascender and does the surface mission.  Crew returns on ascender to NRHO.
4) Ascender left in NRHO for next mission.

Second and subsequent missions:
a) Logistics flight #1 takes 5 t of prop to ascender in NRHO and refuels it.
b) Logistics flight #2 takes 5 t of prop to NRHO and loiters.
c) Orion/Block 1B co-manifests an 11 t, partially fueled lander to NRHO.  Orion undocks and stands off.
d) Logistics flight #2 docks with lander and finishes fueling it.
e) Lander and ascender dock.
f) Crew docks with stacked lander/ascender, transfers, does the mission.
g) Ascender left in NRHO for next mission.

Whenever the ascender is discarded (due to design life or mishap), another full-up Block 1B cargo mission replaces it and the next lander, leaving a Block 1B co-manifest free for Gateway or something else.

This seems... plausible, and it answers the question I've had about why the current Artemis manifest only has one Block 1B cargo launch.  Assuming that NASA can't be bothered with detailing the logistics flights, you can do a mission for two logistics flights and a Block 1B, which is a lot cheaper than two Block 1Bs.

Online TrevorMonty

Re: SpaceX Dragon XL
« Reply #169 on: 03/28/2020 08:43 pm »
My initial though after seeing the art work for this was that it might have a docking adapter at both ends and a pass through tunnel, like one of the proposed follow ons to the ATV. I don't think this is the case as this would limit the volume for external cargo but it's still an idea for a presumably cheap station/free flyer somewhere in the Earth-Moon system.

Sorry only tangentially related to dragon XL, I must try harder :)
Hmm, I was thinking of something different.  We know that NASA is also considering having commercial rockets carry some of the Gateway elements to the assembly point; how would FH do that?

I'm wondering if the Dragon XL is actually modular.  I.e. that smaller section which mates to the FH upper stage is really all power and propulsion (maybe the artist moved the solar panels forward incorrectly).  Then the forward pressurized section is an optional part that gets replaced with external cargo on some missions?  So maybe there is a docking adapter on top, and maybe the bottom feature is just an attachment for Falcon S2?

Also, maybe the propulsion system tanks are big.  Dragon XL should be compatible with Starship of course.  For minimum risk, we’d want it to make Gateway deliveries without using on-orbit refueling.  Also, we’d want to assume the initial Starship is over-weight, so it can’t reach escape energy without that refueling stop (if it can carry 10t to GTO, that’s fine for com sat launches, and it’s also fine for Mars missions as they use refueling anyway). 

So for delta-V, maybe it’s got (.43 km/sec for TLI to NRHO) + (.63 km/s for GTO to TLI) + (.2 km/sec for sub-GTO staging) + (.1 km/s docking and disposal) = 1.36 km/s = 3045 mph.  That an Mr of 1.59 assuming Isp=300s.

Assuming the dry weight is 5 tons and the payload is 5t, the gross weight at launch would be 15.9 tons.  Of course the extra propellant is not needed for FalconH missions, but it doesn’t hurt either.  You either leaving partially filled (less of those expensive hypergolics) or fill them anyway, and it stages in a sub-GTO orbit and still reaches the Gateway.
Slow 3month Hohmann transfer  from LEO to NHRO is about 3km/s compared to faster 3 day direct of about 3.6km/s. Someone said it is being launched to high earth orbit which could shave 1-2km/s off total DV (depends on how high this HEO is) . DV requirements are likely to be in 1-2km/s range, also need to allow for end of life disposal burn to deep space.

Alternatively place it in another lunar obit where it can act as comms relay for few years.


As others have stated I suspect SpaceX will use it as ministation in LEO for extended Dragon tourist flights. I'd add life support but only use it as emergency backup to Dragon's.

Offline ThePonjaX

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Re: SpaceX Dragon XL
« Reply #170 on: 03/28/2020 08:47 pm »
People are trying to project their hopes and dreams onto this thing, but it's just an expendable Dragon 1 variant with a non-tapered "capsule" to fit more cargo.

This isn't going to have an aft docking adapter. It's not going to be recyclable as a station module. It's not going to launch inside a reusable payload fairing. The only reusability potential in this concept is the FH boosters.

If the Gateway comes to fruition, this is a relatively low-cost design evolution for cargo supply. This isn't something that SpaceX would have wanted on their roadmap, and I doubt they anticipate any commercial market for a vehicle like this, but it would have been poor form for SpaceX not to bid. SpaceX has a strategic interest in playing nice with NASA, and while developing Dragon XL would be a distraction, it's not an overly burdensome detour. NASA will pay enough to make it worthwhile for SpaceX even if they're the only conceivable customer.

Maybe (hopefully?) SpaceX won't ever actually have to build one of these. They'll work through the paper milestones and continue to strengthen their relationship with NASA, because that relationship is what will endure the ever-changing roadmaps for human exploration.

These is just maturity from SpaceX about NASA and government biding. Remember when they only propose the Startship and they didn't get any contract? Well they now probably give the NASA options:
1) FH + Falcon XL
2) Starship
NASA choose 1 and give them the contract. It's going to be fullfilled? We don't know but SpaceX is in. And that's important. 


Offline pochimax

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Re: SpaceX Dragon XL
« Reply #171 on: 03/28/2020 08:52 pm »
I think only one offer per firm was permitted.

Offline Alexphysics

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Re: SpaceX Dragon XL
« Reply #172 on: 03/28/2020 09:29 pm »
It's not going to launch inside a reusable payload fairing.
I'd bet money it will. SpaceX will at least attempt fairing recovery on most F9/FH launches from here on out.

They haven't attempted to recover a Dragon 1 nose cap, and that's what Dragon XL is mostly likely to sport. Why would this go inside a fairing? That's just unnecessary mass. The lightweight cork SPAM on the Dragon sidewalls is totally adequate for atmospheric launch.

Read the SpaceflightNow article linked upthread. It is launching inside a fairing.

Offline mlindner

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Re: SpaceX Dragon XL
« Reply #173 on: 03/28/2020 09:36 pm »
Has anyone thought that there isn't going to be a second stage? Dragon XL appears large enough to include the second stage itself. Basically they take the Starship design where the second stage is also the spacecraft.
LEO is the ocean, not an island (let alone a continent). We create cruise liners to ride the oceans, not artificial islands in the middle of them. We need a physical place, which has physical resources, to make our future out there.

Offline lrk

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Re: SpaceX Dragon XL
« Reply #174 on: 03/28/2020 09:40 pm »
It's cargo... Is there some hurry to get it into Lunar orbit in like 3 days?

Even direct transfers to NRHO require 5 days or so.  Ballistic capture transfers require 12-20 weeks, but save 500-600 m/s of delta-v.

The real question here is whether the logistics systems are not only for Gateway support, but whether they're also going to be required to carry propellant for Artemis surface missions before the Gateway exists.  For early Artemis, assuming that Boeing gets its way, you have to launch the lander and ascender so much earlier than the crew (because launching two SLSes in less than 6 months is wildly improbable), that storable prop is the only answer, even if they plan to make the ascender eventually reusable.

There are several ways to evolve from that "expendable lander/ascender in one Block 1B" architecture.  The easiest is simply to refuel and reuse the ascender, but to fit the prop for that into one 5 t logistics flight, the ascender can't be more than 4.5 dry mass and payload, which is almost 2x the mass of the Apollo LM, and therefore is... OK?

One would assume that the main reason to refuel the ascender would be to co-manifest a new lander on a single Orion/Block 1B.  But a storable-based lander would be about 16 t wet, which is about 5 t more than one can co-manifest.

So you could do the following with this HLS architecture:

First mission: 
1) Block 1B cargo takes both the lander and ascender to NRHO.
2) Block 1 takes Orion to NRHO once it's built / stacked / rolled-out (IMO, min 6 months later).
3) Crew transfers to lander/ascender and does the surface mission.  Crew returns on ascender to NRHO.
4) Ascender left in NRHO for next mission.

Second and subsequent missions:
a) Logistics flight #1 takes 5 t of prop to ascender in NRHO and refuels it.
b) Logistics flight #2 takes 5 t of prop to NRHO and loiters.
c) Orion/Block 1B co-manifests an 11 t, partially fueled lander to NRHO.  Orion undocks and stands off.
d) Logistics flight #2 docks with lander and finishes fueling it.
e) Lander and ascender dock.
f) Crew docks with stacked lander/ascender, transfers, does the mission.
g) Ascender left in NRHO for next mission.

Whenever the ascender is discarded (due to design life or mishap), another full-up Block 1B cargo mission replaces it and the next lander, leaving a Block 1B co-manifest free for Gateway or something else.

This seems... plausible, and it answers the question I've had about why the current Artemis manifest only has one Block 1B cargo launch.  Assuming that NASA can't be bothered with detailing the logistics flights, you can do a mission for two logistics flights and a Block 1B, which is a lot cheaper than two Block 1Bs.

6 months between SLS missions seems excessive - especially if you are proposing flying both Block 1 and Block 1B they would be using seperate MLs.  Theoretically you could stack one, move it to another VAB high-bay, stack the other, then roll out and launch both back to back, maybe a few weeks apart.  Potentially close enough to avoid boil-off of cryo propellants. 

But this is straying pretty far off topic from Dragon XL.

Offline lrk

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Re: SpaceX Dragon XL
« Reply #175 on: 03/28/2020 09:43 pm »
Has anyone thought that there isn't going to be a second stage? Dragon XL appears large enough to include the second stage itself. Basically they take the Starship design where the second stage is also the spacecraft.

No.  The Falcon upper stage is not designed for more than maybe a day of operation, max - LOX/RP1 and cold gas thrusters are not suitable for long-duration missions.  The systems on Dragon XL will be closely derived from Dragon 1 and 2. 

Besides the only render we have of Dragon XL clearly shows it seperating from a second stage. 

Offline jadebenn

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Re: SpaceX Dragon XL
« Reply #176 on: 03/28/2020 09:47 pm »
because launching two SLSes in less than 6 months is wildly improbable
Not true! Two MLs. Two VAB high bays.

I can see a downtime of at most 90 days between a dual launch profile to allow for the second roll-out, on-pad work, and contingency scrubs.

6 months between SLS missions seems excessive - especially if you are proposing flying both Block 1 and Block 1B they would be using seperate MLs.  Theoretically you could stack one, move it to another VAB high-bay, stack the other, then roll out and launch both back to back, maybe a few weeks apart.  Potentially close enough to avoid boil-off of cryo propellants. 
Exactly. Though the configuration changes between Block 1 and Block 1B means it would be far more practical to just equip high bay 1 for Block 1B than it would be to try and use high bay 3 to stack both variants.
« Last Edit: 03/28/2020 09:54 pm by jadebenn »

Offline yg1968

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Re: SpaceX Dragon XL
« Reply #177 on: 03/28/2020 10:11 pm »
People are trying to project their hopes and dreams onto this thing, but it's just an expendable Dragon 1 variant with a non-tapered "capsule" to fit more cargo.

This isn't going to have an aft docking adapter. It's not going to be recyclable as a station module.
MPLM was just a can for cargo until it became a station module when they added some MMOD shielding. ATV is basically a prototype station module, as is Cygnus and Tiangong. Doesn't mean it WILL be used this way, but it can be.

In the Draft RFP, the logistic module was supposed to be able to stay docked for 3 years (if necessary) but in the final RFP, the requirement was reduced to a year but NASA mentions that it would prefer if it was able to last more than a year. But in principle, the missions of the logistic module should last 6 months.

The Dragon XL is expected to be docked for 6 months at Gateway. See below:

Quote from: NASA (Attachment_01_GLS_SOW)
4.1 REQUIRED CAPABILITY

The Contractor shall provide for the safe integration, transport and stowage of NASA-provided cargo, both pressurized and unpressurized, to the Gateway and disposal of NASA-provided cargo upon departure from the Gateway.  The Contractor’s logistics vehicle shall be designed to remain docked to Gateway for one (1) year, with efficient crew access to stowage and payloads but the capability to remain longer than one year should also be considered. The nominal mission docked duration is expected to be six months. . The common launch vehicle configuration shall have one (1) successful flight prior to the GLS Missions.
 
https://forum.nasaspaceflight.com/index.php?topic=48353.msg2018139#msg2018139

The Draft RFP had it at 3 years:

Quote from: NASA (Draft Attachment_01_GLS_SOW)
4.1 REQUIRED CAPABILITY
The Contractor shall provide for the safe integration transport and stowage of NASA provided cargo, both pressurized and unpressurized to the Gateway and disposal of NASA provided cargo upon departure from the Gateway. The Contractor’s logistics vehicle shall be designed to remain docked to Gateway for three (3) years, with efficient crew access to stowage and payloads. The capability to remain longer should be considered. The common launch vehicle configuration shall have one (1) successful flight prior to the GLS Missions.
« Last Edit: 03/28/2020 10:18 pm by yg1968 »

Offline Okie_Steve

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Re: SpaceX Dragon XL
« Reply #178 on: 03/28/2020 10:12 pm »
Dragon XL will use a faring on FH and looks to be sized to use the current tankage diameter. If there were ever to be an XXL, what is the putative maximum fairing size for FH that might be used to launch it?

Offline Robotbeat

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Re: SpaceX Dragon XL
« Reply #179 on: 03/28/2020 10:13 pm »
Sounds like it could in principle be the basis for their lander bid, too. Part of the ascent stage portion.

(Haven’t heard much speculation on this point, yet.)
« Last Edit: 03/28/2020 10:15 pm by Robotbeat »
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