Author Topic: SpaceX Dragon XL  (Read 219197 times)

Offline Comga

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Re: SpaceX Dragon XL
« Reply #140 on: 03/28/2020 03:59 pm »
Dragon XL is a missed opportunity on naming.  Clearly it should be Lunar Dragon

The “Dragon XL” name hearkens back to Pegasus XL.
Orbital developed Pegasus on private funds.
NASA liked it, but IMO, said they’d love it if with 10% more capacity.
Growing to Pegasus XL was a problematic effort.
Dragon XL is a bit like that.
NASA treating spacecraft subsystems like Lego(r) pieces.
Not that this is necessarily bad.
Skylab comes to mind as an adapted system.

Is there any statement on whether this is a fixed price contract or CPFF/CPAF? 
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline jstrotha0975

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Re: SpaceX Dragon XL
« Reply #141 on: 03/28/2020 04:06 pm »
A modified Dragon XL would make a great lunar Gateway module. Just my 2 cents. Would be better and probably cheaper than using a Cygnus.

Online GWH

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Re: SpaceX Dragon XL
« Reply #142 on: 03/28/2020 04:11 pm »
A modified Dragon XL would make a great lunar Gateway module. Just my 2 cents. Would be better and probably cheaper than using a Cygnus.

Cygnus isn't an expensive vehicle - it has the lowest price of all 3 CRS 2 providers.

Online yg1968

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Re: SpaceX Dragon XL
« Reply #143 on: 03/28/2020 04:12 pm »
Dragon XL is a missed opportunity on naming.  Clearly it should be Lunar Dragon

The “Dragon XL” name hearkens back to Pegasus XL.
Orbital developed Pegasus on private funds.
NASA liked it, but IMO, said they’d love it if with 10% more capacity.
Growing to Pegasus XL was a problematic effort.
Dragon XL is a bit like that.
NASA treating spacecraft subsystems like Lego(r) pieces.
Not that this is necessarily bad.
Skylab comes to mind as an adapted system.

Is there any statement on whether this is a fixed price contract or CPFF/CPAF?

The RFP says that it is an "Indefinite Delivery Indefinite Quantity (IDIQ), Fixed-Price Contract".

Offline jarmumd

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Re: SpaceX Dragon XL
« Reply #144 on: 03/28/2020 04:13 pm »
Confusing point that a Docking system could be berthed (I don't think anyone quite knows how to do this yet)

Actually we do know, since the MRM-1 module launched to the ISS on STS-132 and attached using the SSRMS. mRM-1 used a “hybrid” docking system.



On STS-74, the Mir Docking Module was berthed to the shuttle APAS using the shuttle RMS before the shuttle/DM docked with Mir.
On STS-88, Node 1 was berthed to the shuttle APAS using the shuttle RMS, then FGB was berthed to Node 1 APAS using the shuttle RMS, to form the initial ISS complex.

Berthing a vehicle/module using a docking mechanism has multiple precedents.

Cool!  I didn't know that!

I guess my thinking was that both SpaceX and NASA have development work to do to be able to do this.  It's not that is isn't possible, obviously it's been done before, but the operations and flight software doesn't yet support it.  There are some ways it could be done easier than others, for instance if the docking system goes through it's regular retraction or starts at ready to hook.
« Last Edit: 03/29/2020 12:25 am by gongora »

Online Ronsmytheiii

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Re: SpaceX Dragon XL
« Reply #145 on: 03/28/2020 04:18 pm »
On STS-74, the Mir Docking Module was berthed to the shuttle APAS using the shuttle RMS before the shuttle/DM docked with Mir.
On STS-88, Node 1 was berthed to the shuttle APAS using the shuttle RMS, then FGB was berthed to Node 1 APAS using the shuttle RMS, to form the initial ISS complex.

Berthing a vehicle/module using a docking mechanism has multiple precedents.

However, on both STS-74 and STS-88, the orbiter had to fire its RCS thrusters to engage the docking mechanism. As far as I know, only the MRM-1 has been berthed using a docking system without any thruster firing.

Offline Jorge

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Re: SpaceX Dragon XL
« Reply #146 on: 03/28/2020 04:22 pm »
On STS-74, the Mir Docking Module was berthed to the shuttle APAS using the shuttle RMS before the shuttle/DM docked with Mir.
On STS-88, Node 1 was berthed to the shuttle APAS using the shuttle RMS, then FGB was berthed to Node 1 APAS using the shuttle RMS, to form the initial ISS complex.

Berthing a vehicle/module using a docking mechanism has multiple precedents.

However, on both STS-74 and STS-88, the orbiter had to fire its RCS thrusters to engage the docking mechanism.

That's unique to APAS. NDS is designed not to require post-contact thrusting.
JRF

Offline jarmumd

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Re: SpaceX Dragon XL
« Reply #147 on: 03/28/2020 04:29 pm »
On STS-74, the Mir Docking Module was berthed to the shuttle APAS using the shuttle RMS before the shuttle/DM docked with Mir.
On STS-88, Node 1 was berthed to the shuttle APAS using the shuttle RMS, then FGB was berthed to Node 1 APAS using the shuttle RMS, to form the initial ISS complex.

Berthing a vehicle/module using a docking mechanism has multiple precedents.

However, on both STS-74 and STS-88, the orbiter had to fire its RCS thrusters to engage the docking mechanism.

That's unique to APAS. NDS is designed not to require post-contact thrusting.

Talking a few different things there.  APAS requires a lot of force to comply the soft capture mechanism (docking suspension / attenuation system).  NDS / SpaceX do not require PCT, but they still need some amount of docking energy.  Now an arm probably has plenty of force to push the soft capture latches in if the mechanism is well aligned.  If it's not aligned and needs to comply the SCS, then maybe not.  Which brings up, would you berth with the SCS deployed or retracted?

Offline freda

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Re: SpaceX Dragon XL
« Reply #148 on: 03/28/2020 04:30 pm »
For some reason, I sense that the one single Marketing Department image we seem to have (post #1 of this thread) might be more of a Proposal-level concept, rather than anything we should put too much consideration into?  Is there ANY other visualization of Dragon-XL?  You know, I'm just thinking of the historical track-record between the first Marketing image of something verses what actually squirts out from production.  Any thoughts?

Offline jarmumd

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Re: SpaceX Dragon XL
« Reply #149 on: 03/28/2020 04:34 pm »
For some reason, I sense that the one single Marketing Department image we seem to have (post #1 of this thread) might be more of a Proposal-level concept, rather than anything we should put too much consideration into?  Is there ANY other visualization of Dragon-XL?  You know, I'm just thinking of the historical track-record between the first Marketing image of something verses what actually squirts out from production.  Any thoughts?

LOL, then what would be the point of the forum?  *you aren't wrong

Online GWH

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Re: SpaceX Dragon XL
« Reply #150 on: 03/28/2020 04:40 pm »
For some reason, I sense that the one single Marketing Department image we seem to have (post #1 of this thread) might be more of a Proposal-level concept, rather than anything we should put too much consideration into?  Is there ANY other visualization of Dragon-XL?  You know, I'm just thinking of the historical track-record between the first Marketing image of something verses what actually squirts out from production.  Any thoughts?

Take a look at all the posts made by woods170 on this subject as that person seems to have a source that has provided confirmation of details as shown being correct to what will be worked on.

Offline rakaydos

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Re: SpaceX Dragon XL
« Reply #151 on: 03/28/2020 04:51 pm »
For some reason, I sense that the one single Marketing Department image we seem to have (post #1 of this thread) might be more of a Proposal-level concept, rather than anything we should put too much consideration into?  Is there ANY other visualization of Dragon-XL?  You know, I'm just thinking of the historical track-record between the first Marketing image of something verses what actually squirts out from production.  Any thoughts?
counterpoint: what is the SpaceX Marketing Department? (other than elon himself)
Where are their offices, what do their linked-in pages say?

SpaceX in general doesnt seem to do separate marketing. They can make presentations, but those presentations tend to be heavier on engineering details (as they stand when the presentation is created) than Marketing would be.

Online wannamoonbase

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Re: SpaceX Dragon XL
« Reply #152 on: 03/28/2020 04:51 pm »
For some reason, I sense that the one single Marketing Department image we seem to have (post #1 of this thread) might be more of a Proposal-level concept, rather than anything we should put too much consideration into?  Is there ANY other visualization of Dragon-XL?  You know, I'm just thinking of the historical track-record between the first Marketing image of something verses what actually squirts out from production.  Any thoughts?

It's 4 years away, that is forever in SpaceX terms, who knows what is possible with Starship or the revenue that Starlink is generating by then.  Maybe Dragon XL will be preceeded by a SS on the lunar surface by then. 

I think your right in that the 1 image we have to work with so far is simplified.  It will look different, the performance specs should be pretty predictable though.

SpaceX is pretty crafty, I'm sure they'll include things that provide residual value to further endeavors.  Perhaps deep space radiation hardening is what they get out of it.
Superheavy + Starship the final push to launch commit!

Online oiorionsbelt

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Re: SpaceX Dragon XL
« Reply #153 on: 03/28/2020 05:00 pm »


It's 4 years away, that is forever in SpaceX terms, who knows what is possible with Starship or the revenue that Starlink is generating by then.  Maybe Dragon XL will be preceeded by a SS on the lunar surface by then. 


This is important. Especially in light of the fact that FH has been approved and has only had 3 flights. SS may have had hundreds of flights in four years time.

Offline DistantTemple

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Re: SpaceX Dragon XL
« Reply #154 on: 03/28/2020 05:07 pm »
For some reason, I sense that the one single Marketing Department image we seem to have (post #1 of this thread) might be more of a Proposal-level concept, rather than anything we should put too much consideration into?  Is there ANY other visualization of Dragon-XL?  You know, I'm just thinking of the historical track-record between the first Marketing image of something verses what actually squirts out from production.  Any thoughts?
counterpoint: what is the SpaceX Marketing Department? (other than elon himself)
Where are their offices, what do their linked-in pages say?

SpaceX in general doesnt seem to do separate marketing. They can make presentations, but those presentations tend to be heavier on engineering details (as they stand when the presentation is created) than Marketing would be.
I had heard one Gwynne Shotwell has from time to time "marketed" SpaceX products.... particularly before there was a rocket factory, or a usefully sized rocket, or rather a usefully sized anything! Maybe that's not marketing.

I think you'll find she still has a role there, and has referred to the odd middle eastern government, or space programme as "her" customers.  ;~)  Maybe Presidents, are just pretty faces!
Edit: You are invited to facepalm.
« Last Edit: 03/28/2020 05:10 pm by DistantTemple »
We can always grow new new dendrites. Reach out and make connections and your world will burst with new insights. Then repose in consciousness.

Online Robotbeat

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Re: SpaceX Dragon XL
« Reply #155 on: 03/28/2020 05:08 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.
« Last Edit: 03/28/2020 05:15 pm by Robotbeat »
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Offline Nathan2go

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Re: SpaceX Dragon XL
« Reply #156 on: 03/28/2020 05:19 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 leave them partially filled (less of those expensive hypergolics) or fill them anyway, and it stages in a sub-GTO orbit (easier S2 disposal) and still reaches the Gateway.
« Last Edit: 03/29/2020 03:00 am by Nathan2go »

Offline ThePonjaX

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Re: SpaceX Dragon XL
« Reply #157 on: 03/28/2020 05:21 pm »
For some reason, I sense that the one single Marketing Department image we seem to have (post #1 of this thread) might be more of a Proposal-level concept, rather than anything we should put too much consideration into?  Is there ANY other visualization of Dragon-XL?  You know, I'm just thinking of the historical track-record between the first Marketing image of something verses what actually squirts out from production.  Any thoughts?

The historical tracking shows Spacex renders and videos are very accurate. Normally they take that from engineers CAD work.  Several times a Spacex video was questioned for that exactly reason: to be just a video for marketing purposes and in the end it was very accurate.

Offline jarmumd

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Re: SpaceX Dragon XL
« Reply #158 on: 03/28/2020 05:24 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.

Offline Jorge

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Re: SpaceX Dragon XL
« Reply #159 on: 03/28/2020 06:18 pm »
If I am reading this correctly, once the robotic arm is installed on Gateway, a berthing option is also required (however, see the post below mine on berthing operations vs berthing mechanisms; the requirements below only require berthing operations to be possible, not a CBM):

Quote from: NASA (Attachment_03_GLS-RQMT-001_Gateway_Logistics_Services_Requirements)
3.10 EXTRAVEHICULAR ROBOTICS COMPATIBILITY

The requirements in this section are applicable to Logistics Vehicles which will dock to Gateway when Extravehicular Robotics capability has been established. [...]

Rationale: The capability for a docked Logistics Module to be relocated to another docking port via the Gateway EVR system reduces Gateway risk and preserves LM consumables.

L3-GLS-1119 Berthing Grapple Fixture Accommodation

The Logistics Module shall have a radially-installed Extravehicular Robotics-compatible Grapple Fixture located within 3.5m (11.5ft) of the docking/berthing port center to enable berthing to Gateway. [...]

Rationale: Gateway operations will need the capability to relocate and berth visiting vehicles using the Robotic Arm. Constraining the relative location of the Grapple Fixture permits manipulator configurations that can provide sufficient push force to overcome resistance forces for all berthing scenarios

https://forum.nasaspaceflight.com/index.php?topic=48353.msg2018139#msg2018139

Edit: to take into account the post below.
I've underlined the critical part. Docking requires to take a hit from the visiting vehicle. This is both a stress (mostly taken by the docking mechanism), and then you have to compensate the delta-v change. So, with berthing, even using IDA, APAS or any other type of IDSS-derived docking system, you save fuel on the gateway AND you reduce the stress.

The stress of docking isn't NASA's primary concern here... I can pretty much guarantee you it's these:
1) The VV suffers failure(s) during free-flight that result in it unable to abort and avoid collision with Gateway (loss of Gateway, crew, and VV)
2) The VV suffers failure(s) during free-flight that result in it able to abort but unable to re-dock with Gateway (loss of VV, threat to mission logistics)

These hazards are inherent, anytime the VV becomes a free-flyer. They can be mitigated by VV fault tolerance but not eliminated. With berthing, there is always at least one rigid attachment (either the docking/berthing mechanism, or the latching end effector on the arm) between the Gateway and the VV, so the VV never becomes a free-flyer, which eliminates the hazards.
« Last Edit: 03/28/2020 06:20 pm by Jorge »
JRF

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