Draft and Final RFP for Gateway logistics/cargo services

[JEF_300]

Ok, but think also that "sample return" is determined to be a "unique cabability"

I thought Dragon 2 was only capable of a one-way trip to the gateway because it lacks the delta-v. That would be great if I'm mistaken.

And, ... what about Cygnus? I think they have the same problem. Or with an "Starliner Gateway Cargo"

The difference is that Cygnus is intended to be totally expendable. After docking to the gateway, a Dragon needs to have enough delta-V left to get back to Earth, while Cygnus just needs enough to get to a disposal orbit.

A cargo variant of Starliner would have the same issue, unless it was also made expendable. If they put an expendable cargo module (say the Pressurized Logistics Module from the Japanese HTV) on top of the Starliner service module, you would get a rather capable Gateway cargo craft.

[pochimax]

I doubt NASA will select two...why?

Today [well, not today]
https://spacenews.com/op-ed-nasa-must-shift-its-focus-to-infrastructure-and-capabilities-that-support-dynamic-missions/

these commercial-based proposals do lack components that the traditional teams have nearly completed, notably a deep space capsule. They are also based on programmatic thinking, full of linear dependencies that recent history suggests will also experience failures and slippages.

Consequently, the correct route forward for NASA is a multilinear one, free of dependence on any one component and focused on building useful infrastructure. A successful, 21st century space agency must gather resources and establish capabilities that can be reconfigured to address changing technical and political climates for years to come. Building such a dynamic kit need not be more expensive and will offer multiple paths to the lunar surface in a competitive process that drives vendors to move quickly at lower costs, rather than embracing caution and seeking higher budgets.

[pochimax]

The difference is that Cygnus is intended to be totally expendable. After docking to the gateway, a Dragon needs to have enough delta-V left to get back to Earth, while Cygnus just needs enough to get to a disposal orbit.

A cargo variant of Starliner would have the same issue, unless it was also made expendable. If they put an expendable cargo module (say the Pressurized Logistics Module from the Japanese HTV) on top of the Starliner service module, you would get a rather capable Gateway cargo craft.

OK, but, please, think that we are talking of evolving from current capabilities in order to achieve the new objectives. It is wrong (in my opinion) to focus only on current characteristics.

The Gateway cargo ships will be new and different from ISS ones, only that not so different (i suppose)

Evolving could go both ways. Downgrading your ship (not returning to earth for Dragon and Starliner) or upgrading it (some kind of sample return for Cygnus).

And it is important to take in to account that NASA wants a base spacecraft and then some options. So it is a complex game. I feel NASA will be unhappy if nobody offer some kind of sample return (obiously, it includes at increment of cost for NASA if chooses this or that option)

[brickmack]

Just gonna kinda shotgun my thoughts on the likely bids:

Dragon 2 Cargo, minimal modification. With a slow transfer (6+ months), any spacecraft can do a TLI-NRHO transfer almost free (under 10 m/s), this is easily within Dragons capabilities. Quick transfer on ONE leg of the journey should be within Dragons delta v capabilities, meeting the 30 day mission-specific option for GLS

    Pros:

        * Minimal development work needed, will be a proven design by the time contracts are awarded

        * Autonomous docking already demonstrated

        * Already supports downmass and unpressurized cargo capacity

        * Reusable capsule on a partially reusable rocket, likely the cheapest option barring Starship

     Cons:

         * unlikely to meet mass requirement due to pressure vessel size

         * likely cannot support robotic arm delivery due to lack of external fixtures for walk-off (not required though)

Cygnus. Similar delta v note to Dragon

    Pros:

        * proven design, and all lunar modification would be qualified by the MHM program anyway

        * easily accomodates mass and volume requirements, even for rapid transit. Multiple configurations available to optimize by mission, can likely stretch SM if needed

        * extensible to years on orbit

        * secondary objectives during transit

    Cons:

         * no return capacity

         * no combined pressurized/unpressurized option, unpressurized variant hasn't flown

         * Northrop already won MHM contract

         * if Omega used, high launch cost and uncertainty of NSSLP award

PPE Derivatives (generic)

    Pros:

        * reusable (at least) propulsion and power systems

        * during docked ops, can significantly augment Gateway power and propulsion capabilities

        * can likely be used as xenon tankers for Gateway

        * potential commonality with tugs/station modules for other applications

    Cons:

        * long transit time (can probably meet rapid transit requirement by launching to TLI on the debut of a new spacecraft, but this requires some coordination of manufacturing and logistics needs)

        * still need separate launch of the cargo itself, either with a reusable delivery vehicle (Dragon, Dream Chaser) or an entire expendable cargo module. Also need LEO docking and possibly hunan labor for cargo transfer

         * limited industry experience with high power electric propulsion

PPE Derivative (SNC)

    Pros:

         * pressurized module derived from Dream Chaser expendable module, reduced cost

         * pressurized module thoroughly integrated into vehicle structure, reduces mass

         * can offer integrated service with Dream Chaser delivering cargo to in-space transport and bringing payload back down

         * SNCs owners have made a *significant* out of pocket payment to develop this vehicle, unlike any other provider

    Cons:

         * SNC has no experience with large GEO comsats, sets them behind the PPE competition

         * composite pressurized module is not yet proven in space

         * unclear how unpressurized cargo would be carried

         * Pressurized docking and human labor in LEO

PPE Derivative (Lockheed, expendable PM, like Jupiter/Exoliner)

    Pros:

       * Benefits from Orion and comsat heritage

        * ditching pressurized module reduces propulsion requirements. Lighter, faster transit

        * replacing the entire cargo module simplifies LEO operations (no pressurized docking, no human labor)

    Cons:

         * no return payload

         * higher per flight cost (offset by not needing separate LEO cargo vehicle?)

PPE Derivative (Boeing):

Pros:

         * benefits from Starliner and comsat heritage

          * downmass via ISS logistics vehicles?

    Cons:

        * pressurized docking and possibly human labor in LEO

PPE Derivative (Northrop):

Pros:

         * benefits from Cygnus and comsat heritage

          * downmass via ISS logistics vehicles?

    Cons:

        * pressurized docking and possibly human labor in LEO

International collaboration with HTV-X and an American integrator:

Pros:

    * high heritage, will soon be flying in LEO

    * large pressurized and unpressurized payload

Cons:

     * no return payload

     * not American enough

IMO Dragon 2 and the SNC PPE are the strongest bids, provided that NASA can be convinced to accept lower mass delivered per mission. If not, Cygnus and SNC PPE. I don't see multiple PPE derivatives having a shot due to travel time, and of the bunch, SNC is in the best position given their existing funding and NASAs comments on their Gateway PPE bid.

[TrevorMonty]

The only things that could need returning would be lunar samples and crew health experiment samples, both of which can be returned in Orion.

I don't see NASA objecting to SpaceX returning Dragon but only benefit would be chance for SpaceX to reuse Dragon. Doubt its worth extra cost and Dragon may not be reuseable after high speed reentry.

[JEF_300]

If I'm recalling this from the H3 thread properly, the H3 is designed to handle up to 8 SRBs. In that configuration, the H3 might be able to send the HTV-X out to Gateway. Just a thought.

[su27k]

Anybody know the best way for Dragon to meet the pressurized cargo requirement?

Contractor shall provide a capability to deliver a minimum of 3,400 kg of
pressurized cargo to the Gateway within the overall constraints as defined in GLSRQMT-001.

For reference, the sizes, mass properties, resource interfaces, environmental requirements
and strapping/attachment interfaces for the MDL and CTB cargo and payloads are
provided in SSP-50833, International Space Station Program Cargo Transport
Interface Requirements Document, and may be used as a guideline. Note, typical
ISS cargo packing density for CTBs is approximately 290 kg/m3
. .

1.)Dragon has never came close to delivering 3400 kg of pressurized cargo.
2.)Dragon 2 with a pressurized volume of 9.3 cubic meters (wikipedia) and a payload density of 290 kg (per cubic meter) only nets you 2697 kg which is consistent with delivered cargo on past CRS missions.

You could: add an additional cargo carrier to the trunk, enlarge the pressure vessel or ..

This of course opens a can of worms. Once you start changing the pressure vessel, it starts looking like a different spacecraft. But ports on gateway are probably driving the minimum cargo per mission requirement and so the 3400 kg may only be able to use one port. In addition, the cargo services have to be delivered prior to arm arrival. That means you have two interfaces on the pressurized module in the trunk - one to interface with the dragon and one to interface with the gateway. This dance that is required prior to docking to remove the pressurized module from the trunk and attach it the end of dragon is similar to what was done for Apollo, but that was essentially two different complete fully capable spacecraft.

Assuming you go with the enlarge pressure vessel route, this suggestion from upthread seems the easiest (except the larger trunk part, I don't think you need to change the external dimension of the trunk, just need to move the whipple shield and unpressurized cargo rack downward):

Dragon is smaller than NASA really wanted for CRS, I don't see it being competitive for the Gateway missions without extensive mods (go expendable, ditch the heat shield, cut a hole in the bottom and put more pressurized space in a larger trunk?)

Doesn't change OML, minimal change to everything except the pressure vessel.

But this may not be necessary, SpaceX already said they're changing the weldment (I believe this is the same as pressure vessel) for Cargo Dragon 2, and they're also developing new pressurized cargo packing design for Cargo Dragon 2, these two together may already be able to solve the volume issue.

[Tywin]

The difference is that Cygnus is intended to be totally expendable. After docking to the gateway, a Dragon needs to have enough delta-V left to get back to Earth, while Cygnus just needs enough to get to a disposal orbit.

A cargo variant of Starliner would have the same issue, unless it was also made expendable. If they put an expendable cargo module (say the Pressurized Logistics Module from the Japanese HTV) on top of the Starliner service module, you would get a rather capable Gateway cargo craft.

OK, but, please, think that we are talking of evolving from current capabilities in order to achieve the new objectives. It is wrong (in my opinion) to focus only on current characteristics.

The Gateway cargo ships will be new and different from ISS ones, only that not so different (i suppose)

Evolving could go both ways. Downgrading your ship (not returning to earth for Dragon and Starliner) or upgrading it (some kind of sample return for Cygnus).

And it is important to take in to account that NASA wants a base spacecraft and then some options. So it is a complex game. I feel NASA will be unhappy if nobody offer some kind of sample return (obiously, it includes at increment of cost for NASA if chooses this or that option)

The Dream Chaser cargo is perfect to bring the sample return to the Earth in good shape...

[Tywin]

If I'm recalling this from the H3 thread properly, the H3 is designed to handle up to 8 SRBs. In that configuration, the H3 might be able to send the HTV-X out to Gateway. Just a thought.

And could be a way of Jaxa for pay the seats of the Japanese astronauts to the Moon, they will send in the Orion...sorry for me thought, a little off topic...

[gongora]

But this may not be necessary, SpaceX already said they're changing the weldment (I believe this is the same as pressure vessel) for Cargo Dragon 2, and they're also developing new pressurized cargo packing design for Cargo Dragon 2, these two together may already be able to solve the volume issue.

They're making those changes to meet the CRS-2 requirements, which are far less than the Gateway requirements.

[envy887]

Anybody know the best way for Dragon to meet the pressurized cargo requirement?

Contractor shall provide a capability to deliver a minimum of 3,400 kg of
pressurized cargo to the Gateway within the overall constraints as defined in GLSRQMT-001.

For reference, the sizes, mass properties, resource interfaces, environmental requirements
and strapping/attachment interfaces for the MDL and CTB cargo and payloads are
provided in SSP-50833, International Space Station Program Cargo Transport
Interface Requirements Document, and may be used as a guideline. Note, typical
ISS cargo packing density for CTBs is approximately 290 kg/m3
. .

1.)Dragon has never came close to delivering 3400 kg of pressurized cargo.
2.)Dragon 2 with a pressurized volume of 9.3 cubic meters (wikipedia) and a payload density of 290 kg (per cubic meter) only nets you 2697 kg which is consistent with delivered cargo on past CRS missions.

You could: add an additional cargo carrier to the trunk, enlarge the pressure vessel or ..

This of course opens a can of worms. Once you start changing the pressure vessel, it starts looking like a different spacecraft. But ports on gateway are probably driving the minimum cargo per mission requirement and so the 3400 kg may only be able to use one port. In addition, the cargo services have to be delivered prior to arm arrival. That means you have two interfaces on the pressurized module in the trunk - one to interface with the dragon and one to interface with the gateway. This dance that is required prior to docking to remove the pressurized module from the trunk and attach it the end of dragon is similar to what was done for Apollo, but that was essentially two different complete fully capable spacecraft.

The easiest thing to do if they need more pressurized volume is to extend the cylindrical ECLSS section under the "floor" into the trunk. This would go through the heatshield, but if downmass isn't valuable they can dispense with the heat shield entirely anyway. Based on the density above, they need 3 cubic meters, which this should easily achieve.

Or they can ask NASA if they are interested in a little lower upmass, but with some downmass capability.

[Negan]

The easiest thing to do if they need more pressurized volume is to extend the cylindrical ECLSS section under the "floor" into the trunk.

By far the best option. Not anymore complex than how Cygnus is extended and the added bonus of not having to launch in a fairing.

Edit: I see some claiming a hole would have to be cut in the bottom, but this section is clearly open to the rest of the pressure vessel and could be easily extended. Dragon 1 already had the option of an extended trunk so Dragon 2's trunk can likely be extended also if needed (no LES so no fins needed). Eliminating reentry components due to making it expendable would only make it lighter and cost less.

[su27k]

But this may not be necessary, SpaceX already said they're changing the weldment (I believe this is the same as pressure vessel) for Cargo Dragon 2, and they're also developing new pressurized cargo packing design for Cargo Dragon 2, these two together may already be able to solve the volume issue.

They're making those changes to meet the CRS-2 requirements, which are far less than the Gateway requirements.

But when IG asked SpaceX why they increased price for CRS-2, one of the reason SpaceX gave is that they had to redesign the vehicle to increase payload volume by 30%, not sure if this is comparing to Dragon 1 or Crew Dragon but I think both Dragon 1 and Crew Dragon use the same pressure vessel, so it seems to me there is the possibility that they're working on a big increase of pressurized volume for Cargo Dragon 2.

[gongora]

But this may not be necessary, SpaceX already said they're changing the weldment (I believe this is the same as pressure vessel) for Cargo Dragon 2, and they're also developing new pressurized cargo packing design for Cargo Dragon 2, these two together may already be able to solve the volume issue.

They're making those changes to meet the CRS-2 requirements, which are far less than the Gateway requirements.

But when IG asked SpaceX why they increased price for CRS-2, one of the reason SpaceX gave is that they had to redesign the vehicle to increase payload volume by 30%, not sure if this is comparing to Dragon 1 or Crew Dragon but I think both Dragon 1 and Crew Dragon use the same pressure vessel, so it seems to me there is the possibility that they're working on a big increase of pressurized volume for Cargo Dragon 2.

The increase was from CRS-1.  The OIG report shows the pressurized upmass for Cargo Dragon 2 as 2507kg.  This is with the increase in pressure vessel size.  It would need another large increase to meet the requirements for the Gateway solicitation.  Dragon 1 and Crew Dragon don't use the same pressure vessel.

[pochimax]

For slow transit, only a few tens of m/s over the required velocity for L1, and then a few tens of meters/s delta-v to stop in NHRO is required as I understand it.

the dracos would be just fine for this low delta-v.
-----

A thought I've not seen asked yet.
FH has demonstrated a coast of 6h.
FH with one core expended has a payload of ~55 tons to TLI.
TLI is nominally ~3100m/s or so.

With a 9 ton (plus 2 ton S2 payload), the total delta-v available is 5.4km/s.

An energetic enough burn may be able to place a payload in NHRO with a coast not enormously longer than that already demonstrated.

As far as I know, braking to reach the NHRO orbit after TLI could be a delta v of 450 m/s

It could be done only with Dracos?

Draco engines are expected to work only for maneouvering, isnt' it?

Thanks everybody

[mmeijeri]

As far as I know, braking to reach the NHRO orbit after TLI could be a delta v of 450 m/s

That's for fast trajectories.

[pochimax]

As far as I know, braking to reach the NHRO orbit after TLI could be a delta v of 450 m/s

That's for fast trajectories.

Thanks!!

But, the architecture has a problem or maybe I am wrong.

SpaceX can use Falcon Heavy to launch Dragon in a fast trajectory to Gateway' s NRHO orbit... but can' t do braking only with Dracos. So it is supposed SuperDracos would be needed.

On the other hand, if SpaceX chooses a slowest trajectory to reach Gateway, it can' t be done only with second stage, because it can' t live so many time and so many ignitions. Again SuperDracos would be needed.

So, my questions.

It could be done simply using the superdracos and propellants onboard the cargo Dragon?

It could be needed  to develop some kind of transfer stage coupled with Dragon, with all the propellants and neither dracos nor propellants for them in the cargo Dragon?

Or I am completely wrong and the mission could be done only with Falcon Heavy and draco enginges?

[TripleSeven]

The only things that could need returning would be lunar samples and crew health experiment samples, both of which can be returned in Orion.

I don't see NASA objecting to SpaceX returning Dragon but only benefit would be chance for SpaceX to reuse Dragon. Doubt its worth extra cost and Dragon may not be reuseable after high speed reentry.

yes...what will be interesting to see is if OSC continues to develop the (talked about) capability of their module to reenter through that large inflatable heat shield that I think LaRC is developing

that could be a game changer from lunar orbit

[speedevil]

SpaceX can use Falcon Heavy to launch Dragon in a fast trajectory to Gateway' s NRHO orbit... but can' t do braking only with Dracos. So it is supposed SuperDracos would be needed.

The braking does not need to be instantaneous - it's not landing on the moon.
The Draco thrusters already do ~250m/s or so per mission, and there are 18 of them - 1200N in each axes + and -.

At 10 tons mass, 1200N leads to needing around a 400s burn, which is for these purposes instantaneous.

The lifetime of the Draco engines isn't really in question either, because if you have to, you can use more than one axes (200s on +z, flip and 200s on -z).

It is at most a modest increment over the total nominal mission firing time to ISS.
Superdracos are pointless weight for this.

[pochimax]

SpaceX can use Falcon Heavy to launch Dragon in a fast trajectory to Gateway' s NRHO orbit... but can' t do braking only with Dracos. So it is supposed SuperDracos would be needed.

The braking does not need to be instantaneous - it's not landing on the moon.
The Draco thrusters already do ~250m/s or so per mission, and there are 18 of them - 1200N in each axes + and -.

At 10 tons mass, 1200N leads to needing around a 400s burn, which is for these purposes instantaneous.

The lifetime of the Draco engines isn't really in question either, because if you have to, you can use more than one axes (200s on +z, flip and 200s on -z).

It is at most a modest increment over the total nominal mission firing time to ISS.
Superdracos are pointless weight for this.

So, if I have understood you properly, you think SpaceX could do the mission only with Falcon Heavy + future Dragon v2, without using superdracos.  (30 days mission)

(this pointing is only for having a simpler and clearer picture of that kind of mission, on my mind...)

thanks