ISS Commercial Resupply Services 2 (CRS2) 2017-2030

[abaddon]

Why would SpaceX need to make investments for CRS2? Can't they just offer Dragon V1 and V2? There was talk of an extended trunk. But I don't think SpaceX has other plans for improving Dragon.

SpaceX has also talked (vaguely) about transitioning to V2 only at some point.  As others have noted Dragon V2 itself has several drawbacks from a cargo perspective.  An optional extended trunk with a removable pressurized cargo module (and CBM interface) could be a relatively cost effective way to achieve cargo and crew with the same system.  Maybe even simultaneously, as in the old Liberty proposal (the best feature of that proposal, in my opinion).

[kevinof]

Does the F9 have the lift capability to do a crew and cargo at the same time?

[abaddon]

Does the F9 have the lift capability to do a crew and cargo at the same time?

That is probably unclear until we know the actual Dragon V2 and trunk mass, but I would say tentatively "yes", by some amount.  Not as confident that it would end up being enough to make it worthwhile.  However, it is possible with some small incremental improvements to F9 that SpaceX has mentioned (propellant densification, increased Merlin thrust) that they could squeeze out enough improvement in LEO capacity of F9 to eat the difference in the mass penalty of the extended trunk and pressurized module at some point in the CRS2 contract timeline.

[baldusi]

ISTM, not for pressurized cargo.  That said, aren't the major drivers in Cygnus expansion how many segments are in the pressure vessel and perhaps an increased prop margin? Doesn't sound that difficult.

There's a presentation of a super Cygnus with an extra pressurized ring (four total) that has a mass capability of 3,400kg and 33m³. But it would require something like 5,500kg to 300km x 51.6deg from the Antares. The 131 can do 5,260kg and it would also require an extra fairing extension. If the new re-engined Antares can get the extra performance, the total cost to OSC of this development will be quite low.
I believe that the SpaceX solution that I propose is also relatively cheap. But in general it's quite clear that SNC, Boeing, SpaceX and OrbitalATK will need some investments for CRS-2 and thus I expect a pretty leveled field.

Why would SpaceX need to make investments for CRS2? Can't they just offer Dragon V1 and V2? There was talk of an extended trunk. But I don't think SpaceX has other plans for improving Dragon.

The request is for 15 to 17 tonnes of pressurized cargo, 55m3 to 70m3 of volume and no more than 5 launches (everything per year). Since dragon v1 has just 10m3 of pressurized , and at an average density of 150kg/m3 they simply can't quite cover the volume, nor mass within the missions limits. And Dragon v2 parachute position appears to prevent the use of a CBM. I ignore if the v2 pressure vessel has an extra m3 of volume available, and if they can simply use the v1 parachute system for the v2 Cargo version.
But the pressing issue is the cargo density.

[rpapo]

I ignore...

I don't know...

Tenga cuidado con las palabras que se parecen entre el inglés y el español...

[guckyfan]

But the pressing issue is the cargo density.

Yes. Maybe NASA should rethink their packing methods. With todays packing materials it should be possible to pack denser without sacrificing safety.

[Kryten]

 What kind of volume and mass does dreamchaser carry? Could it fill the requirements?

[yg1968]

The IG says that SpaceX would meet the requirements for CRS2 (see table 4 on page 26 of the report). That is also my understanding. The number of flights (5) isn't a hard requirement either. See below.

That RFI requests up to 16.8 tonnes of pressurized upmass yearly with a volume of up to 70 m^3. The maximum allowed number of flights is 5 yearly, so this works out to 3.4 tonnes and 14 m^3 per flight.

A dragon has only 11 m^3 of pressurized volume (http://www.spacex.com/dragon), so a larger dragon is presumably required. I have no idea whether a F9 1.1 would be sufficient to haul an enlarged dragon to ISS.

I'll just note that you quote "up to" 3.4 tonnes and 14 m^3. If that's the language from the original, then that would simply to me imply an upper bound, or a rough ballpark they'd like. I think you could also mix-and-match payloads between operators: put denser payloads into Dragon, and save lighter, bulkier ones for Cygnus. (Just to pick a combination of the two existing vehicles.)

The RFI says that it should generally represent 55 to 70 m^3. It doesn't seem to be a hard requirement. But SpaceX would meet it anyways. They should also meet the payload requirement 5 x 3 mt = 15mt.

Delivery of 14,250 to 16,750 kilograms (kg) per year of pressurized cargo.
o The typical volume of the mass of cargo quoted above is 55 to 70 cubic meters (m3) which must be accommodated.

[baldusi]

The IG says that SpaceX would meet the requirements for CRS2 (see table 4 on page 26 of the report). That is also my understanding. The number of flights (5) isn't a hard requirement either. See below.

That RFI requests up to 16.8 tonnes of pressurized upmass yearly with a volume of up to 70 m^3. The maximum allowed number of flights is 5 yearly, so this works out to 3.4 tonnes and 14 m^3 per flight.

A dragon has only 11 m^3 of pressurized volume (http://www.spacex.com/dragon), so a larger dragon is presumably required. I have no idea whether a F9 1.1 would be sufficient to haul an enlarged dragon to ISS.

I'll just note that you quote "up to" 3.4 tonnes and 14 m^3. If that's the language from the original, then that would simply to me imply an upper bound, or a rough ballpark they'd like. I think you could also mix-and-match payloads between operators: put denser payloads into Dragon, and save lighter, bulkier ones for Cygnus. (Just to pick a combination of the two existing vehicles.)

The RFI says that it should generally represent 55 to 70 m^3. It doesn't seem to be a hard requirement. But SpaceX would meet it anyways. They should also meet the payload requirement 5 x 3 mt = 15mt.

Delivery of 14,250 to 16,750 kilograms (kg) per year of pressurized cargo.
o The typical volume of the mass of cargo quoted above is 55 to 70 cubic meters (m3) which must be accommodated.

I've been reading the report. And they use the nominal Dragon and Cygnus numbers, not actual achieved. And they don't post the volume. They barely say that the density limitation might mean that they can't even achieve the nominal numbers. The nice part is that they would still be under budget, since both current prices are significantly under their expected cap.

[yg1968]

I thought that the actual numbers acheived were less because of volume constraints not because of capability issues.

[baldusi]

I thought that the actual numbers acheived were less because of volume constraints not because of capability issues.

I never implied anything but density limitations for Dragon (Cygnus is performance limited, for now).

[yg1968]

I thought that the actual numbers acheived were less because of volume constraints not because of capability issues.

I never implied anything but density limitations for Dragon (Cygnus is performance limited, for now).

OK. But I am just wondering if the 15mt per year upmass requirement is a performance limit or is it what NASA needs to bring up to the ISS each year. I am still not clear on that.

[A_M_Swallow]

SpaceX has also talked (vaguely) about transitioning to V2 only at some point.  As others have noted Dragon V2 itself has several drawbacks from a cargo perspective.  An optional extended trunk with a removable pressurized cargo module (and CBM interface) could be a relatively cost effective way to achieve cargo and crew with the same system.  Maybe even simultaneously, as in the old Liberty proposal (the best feature of that proposal, in my opinion).

Would this arrangement allow Dragon to lift something large like a new solar array or radiator?

[clongton]

Does the F9 have the lift capability to do a crew and cargo at the same time?

One of the major findings of the CAIB which lead directly to the cancellation of Shuttle as soon after RTF as possible, was that mixing crew and cargo within the confines of the same spacecraft was a definitive contributing factor to the loss of the Columbia crew. The recommendation was for NASA to use separate spacecraft for cargo so that crew would not be placed at risk for the sake of cargo delivery.

[GreenShrike]

One of the major findings of the CAIB which lead directly to the cancellation of Shuttle as soon after RTF as possible, was that mixing crew and cargo within the confines of the same spacecraft was a definitive contributing factor to the loss of the Columbia crew. The recommendation was for NASA to use separate spacecraft for cargo so that crew would not be placed at risk for the sake of cargo delivery.

Doesn't fly. Crewed Dragons are going up regardless, so the flights are for the sake of ISS crew replacement, not cargo delivery. Adding cargo to a DragonRider flight doesn't change the necessity of risking crew on an orbital launch.

[ChrisWilson68]

One of the major findings of the CAIB which lead directly to the cancellation of Shuttle as soon after RTF as possible, was that mixing crew and cargo within the confines of the same spacecraft was a definitive contributing factor to the loss of the Columbia crew. The recommendation was for NASA to use separate spacecraft for cargo so that crew would not be placed at risk for the sake of cargo delivery.

Doesn't fly. Crewed Dragons are going up regardless, so the flights are for the sake of ISS crew replacement, not cargo delivery. Adding cargo to a DragonRider flight doesn't change the necessity of risking crew on an orbital launch.

But adding additional modules increases complexity, and that might lead to unanticipated increases in risk.

If the crew vehicle has seats that aren't being used anyway, throwing in some cargo instead of passengers seems fine to me.  Adding big new trunks and/or pressurized modules crosses the line for me to adding that risk the CAIB warned about.

[robertross]

One of the major findings of the CAIB which lead directly to the cancellation of Shuttle as soon after RTF as possible, was that mixing crew and cargo within the confines of the same spacecraft was a definitive contributing factor to the loss of the Columbia crew. The recommendation was for NASA to use separate spacecraft for cargo so that crew would not be placed at risk for the sake of cargo delivery.

Doesn't fly. Crewed Dragons are going up regardless, so the flights are for the sake of ISS crew replacement, not cargo delivery. Adding cargo to a DragonRider flight doesn't change the necessity of risking crew on an orbital launch.

But adding additional modules increases complexity, and that might lead to unanticipated increases in risk.

If the crew vehicle has seats that aren't being used anyway, throwing in some cargo instead of passengers seems fine to me.  Adding big new trunks and/or pressurized modules crosses the line for me to adding that risk the CAIB warned about.

That would be NASA's (and the astronaut office's) call though.
That's why there is a resupply vehicle (and cargo return with Dragon).
But obviously Soyuz has that flexibility, so again, we'll have to wait and see.

I'd love to see the science brought back (the whole purpose of the ISS), but I would never think of adding increased risk to the crew to see it through (but that's just me)

[gongora]

I'm sure it would be a lot more complex and costly than putting a pressurized container in the trunk, but would it be feasible to make a cargo Dragon in a Soyuz-like configuration with a second pressurized module on top?  Seems like it would be much easier to actually use at the ISS.

[darkenfast]

I'm sure it would be a lot more complex and costly than putting a pressurized container in the trunk, but would it be feasible to make a cargo Dragon in a Soyuz-like configuration with a second pressurized module on top?  Seems like it would be much easier to actually use at the ISS.

First, it would make the whole abort system MUCH more difficult.  Second, that module would probably weigh several thousand pounds.  Third, it would mean throwing away a pressurized module, its hatch(es), and the docking mechanism, all of which would run counter to the direction SpaceX is moving in.  I'm just guessing, but I think Spacex will stick with the limitations of Dragon for the near future, at least. 

[Patchouli]

What kind of volume and mass does dreamchaser carry? Could it fill the requirements?

I read some where it has 16m3 of volume and probably has more down mass then any of the other vehicles.

So going for cargo could be a good option for SNC since their vehicle has an advantage over both Dragon and the CST-100 in pressurized volume.

The stretched Cygnus beats it in up cargo volume but SNC is using the more powerful Atlas V rocket so mass is less limited on DC.

Since cargo missions do not need abort engines if they are uncrewed I wonder could they replace the hybrid propulsion system with a couple of low thrust propellant engines such as the TR-308.

Maybe they could even add some sorta module to the back that adds more volume and a CBM hatch sorta like what was on the back of the old Hermes concept.
Then launch it on one of the more powerful Atlas variants or even Ariane 5.