Replacing SLS/Orion using Starship HLS and Crew Dragon

[DanClemmensen]

We have managed to drag at least two threads off topic discussing this:
Crew Dragon Mission Life Extension: Free-Flying, Uncrewed Duration
  https://forum.nasaspaceflight.com/index.php?topic=59657.0
NASA HLS (Human Landing System) Lunar Landers]
  https://forum.nasaspaceflight.com/index.php?topic=46645.0

So I think a new thread is more appropriate. Moderators, please move this thread if it's in the wrong place.

Lots of folks think SLS and Orion are far too expensive and do not provide enough functionality for a robust Artemis program. So what is the minimal modification to Artemis to fix this?

I think a minimal approach is needed:
   1) Maintain the Artemis program as is to the extent possible.
   2) Cancel SLS and Orion as soon as is feasible.
   3) Minimize use of new hardware.

Within Artemis, SLS/Orion exists to take four astronauts per mission from Earth to NHRO and back to earth, so the minimal approach would implement this functionality. the concept is to use Crew Dragon for Earth to LEO and back, and use an OTV to convey them from LEO to NRHO and back.  Instead of a new-design OTV,  use a second instance of Starship HLS. Same hardware, different functionality.

One problem with this is that Crew Dragon must remain in LEO for many days. This can be fixed in several ways:
   1) Just fly two Dragons, one for Earth-to-LEO transfer and another for LEO-to-Earth transfer. No new hardware, but it's expensive.
   2) Modify Crew Dragon to support a long uncrewed loiter:  This need a modification to a crew-qualified spacecraft, which may lengthen the schedule.
   3) Fly a third unmodified instance of HLS to act as a CLD. Dragon can dock to the CLD, which can sustain it.

Even the brute-force approach using two Crew dragons will almost certainly be cheaper than SLS/Orion. A short Crew Dragon mission apparently costs $200 million or less. The OTV mission would cost at most the same as an HLS mission, and we know that the Artemis IV HLS mission was priced at $1.13 billion million including development. Second and succeeding missions can reuse the OTV and the CLD.

Enhancements:
    The use of unmodified HLS is a kludge. I think one minor(?) enhancement to HLS will simplify the mission and add flexibility later: add a second IDSS port. With this enhancement, Crew Dragon and OTV HLS can dock to CLD HLS at the same time. This modification might be minor because HLS is still in the design phase.

[alugobi]

So what is the minimal modification to Artemis to fix this?

Congress.

[DanClemmensen]

So what is the minimal modification to Artemis to fix this?

Congress.

That's not minimal. One big concern that started all this was what to do if a faction in congress decides to cut SLS/Orion. What should NASA propose as an alternative to abandoning Artemis?

[alugobi]

"minimal" as in step one.  Any alternative flows from that.

[Zed_Noir]

<snip>

Even the brute-force approach using two Crew dragons will almost certainly be cheaper than SLS/Orion. A short Crew Dragon mission apparently costs $200 million or less. The OTV mission would cost at most the same as an HLS mission, and we know that the Artemis IV HLS mission was priced at $1.13 million including development. <snip>

Think you meant $1.13 billion.

[jarmumd]

Remember, IDSS only represents docking to the International Space Station.  GDSS is the standard for docking to the gateway, and they are not interchangeable for more than an emergency. 

Dragon, CST-100 = IDSS
Orion, HLS = GDSS

They cannot be made interchangeable.  and modifying one to be the other will come with a cost.

Just something to keep in mind as you combine options.

[DanClemmensen]

Remember, IDSS only represents docking to the International Space Station.  GDSS is the standard for docking to the gateway, and they are not interchangeable for more than an emergency. 

Dragon, CST-100 = IDSS
Orion, HLS = GDSS

They cannot be made interchangeable.  and modifying one to be the other will come with a cost.

Just something to keep in mind as you combine options.

I did not know that and I do not disbelieve you, but it's really strange and astoundingly stupid. I knew that Orion was originally intended to be able to dock to ISS, and I have seen possibly incorrect assertions that Gateway uses IDSS. Do you have a reference I can access to educate myself?

[whitelancer64]

Remember, IDSS only represents docking to the International Space Station.  GDSS is the standard for docking to the gateway, and they are not interchangeable for more than an emergency. 

Dragon, CST-100 = IDSS
Orion, HLS = GDSS

They cannot be made interchangeable.  and modifying one to be the other will come with a cost.

Just something to keep in mind as you combine options.

This is not quite correct.

Per GLS-RQMT-001 (the Gateway Logistics Services Requirements, attached below), the Gateway Docking System (GDS) is an IDSS-compatible design, with additional fluid (for refueling the Gateway), electrical, data, and possibly other connections, this compatibility implies that the rest of the docking system's IDSS required parts are not changed. Keep-out zones for such connections are reserved in the current revision (Rev F, July 2022) of the IDSS. Basically, GDSS is a specialized type of IDSS.

An IDSS compliant docking system should be able to dock with the Gateway, but it won't be able to use those other connections. A GDS should likewise be able to dock to the ISS.

The NASA Docking System Block 2 is the NASA developed GDSS-compatible docking system for Orion.

NASA's requirements for Gateway docking systems are specified in DSG-SPEC-MECH-017, Gateway Docking System Specification (GDSS), but unfortunately for us, this document is not publicly available.

[DanClemmensen]

Remember, IDSS only represents docking to the International Space Station.  GDSS is the standard for docking to the gateway, and they are not interchangeable for more than an emergency. 

Dragon, CST-100 = IDSS
Orion, HLS = GDSS

They cannot be made interchangeable.  and modifying one to be the other will come with a cost.

Just something to keep in mind as you combine options.

This is not quite correct.

Per GLS-RQMT-001 (the Gateway Logistics Services Requirements, attached below), the Gateway Docking System (GDS) is an IDSS-compatible design, with additional fluid (for refueling the Gateway), electrical, data, and possibly other connections, this compatibility implies that the rest of the docking system's IDSS required parts are not changed. Keep-out zones for such connections are reserved in the current revision (Rev F, July 2022) of the IDSS. Basically, GDSS is a specialized type of IDSS.

An IDSS compliant docking system should be able to dock with the Gateway, but it won't be able to use those other connections. A GDS should likewise be able to dock to the ISS.

The NASA Docking System Block 2 is the NASA developed GDSS-compatible docking system for Orion.

NASA's requirements for Gateway docking systems are specified in DSG-SPEC-MECH-017, Gateway Docking System Specification (GDSS), but unfortunately for us, this document is not publicly available.

OK. Since the fluids supported by GDSS (hydrazine and Xenon) are not used by Starship HLS, I suspect that Starship HLS will implement IDSS and interoperate properly with Gateway. If Starship HLS must be designed to mate directly with Orion (i.e., if Gateway is not available in time for Artemis III) then HLS will not be transferring fluids to to from Orion and an IDSS interface suffices.
  HOWEVER: the HLS IDSS port must be active/passive, not just active-only, in order to interface with Orion, which I assume is active-only, and with Gateway, which is passive-only. This is not a new requirement added for the SLS/Orion replacement.  Dragon is active-only.

[TheRadicalModerate]

Remember, IDSS only represents docking to the International Space Station.  GDSS is the standard for docking to the gateway, and they are not interchangeable for more than an emergency. 

Dragon, CST-100 = IDSS
Orion, HLS = GDSS

They cannot be made interchangeable.  and modifying one to be the other will come with a cost.

Just something to keep in mind as you combine options.

I thought GDSS was somewhat backward-compatible with IDSS.  You only get power/data umbilicals, but I thought an active IDSS implementation could still dock with a passive GDSS implementation (i.e., with the Gateway ports).  Is that incorrect?

Update:  Ninja'd by whitelancer.  So much for commenting as I go.

[TheRadicalModerate]

I think this is on-topic with what Dan intended:  Here's kinda what I was thinking would be the most iterative evolution of how to get rid of SLS/Orion, using only SpaceX hardware.  (Note that some of this would accommodate incorporation of Blue Moon.)

1) Option A, using SLS/Orion and LSS HLS v1.0.

2) Option B, using SLS/Orion and LSS HLS v1.1.

3) F9/D2 for launch and EDL, qualified/modified for multi-week uncrewed loiter in LEO.  OTV-LSS for LEO-NRHO-LEOpropulsive, with RPODs in NRHO with HLS-LSS.  (Note that OTV-LSS and HLS-LSS are two instances of the same type of vehicle, just different roles.)

4) F9/D2 same as #3, but consolidate OTV-LSS and HLS-LSS into a single vehicle, refueled in NRHO after ascent from the lunar surface.  (Slightly cheaper in terms of prop, especially if you use an EDL-capable tanker for the NRHO refueling.  Probably requires better prop management for the tanker.)

5) On the assumption that NASA would be less terrified crew-rating Starship aerocapture than crew-rating full launch/EDL:  Build v0.5 of an EDL-capble LSS (acronym:  EDLC-LSS), with all the LSS features, but also a TPS system.  It still uses F9/D2 for launch and EDL, but after the crew has completed EDL in the D2, the EDLC-LSS could be landed with down-mass, and heavy unpressurized cargo could be reloaded into the garage.

Note:  This is a pretty big iteration, because a nose-mounted docking system isn't going to work.  You need the nose header tanks to maintain balance during entry, so you have to work out some kind of dorsal docking system.  A possibility:  integrate the docking hardware into one or both airlocks on the cargo deck (aka "the garage").  It obviously has to accomodate D2, but if you later want to do Starship-to-Starship or EDLC-LSS-to-Starship using the same system, you have to figure out Starship dorsal-to-dorsal docking for crew transfer.

6) EDLC-LSS with full-blown crew certification for launch EDL.

SLS/Orion is required only for #1 and #2, but can continue on with #3 and #4, possibly alternating missions.  Orion could work with #5, but since it wouldn't go past LEO, it'd be stupid.  And SLS/Orion still launching with #6 is just sad.

[TheRadicalModerate]

Just so I can feel virtuous about being on-topic, the issue here is that the LSS would have to be able to dock with D2's active IDA¹ and also be able to dock with Orion's NDS and Gateway's GDA.¹  This would have to be supported before the D2/LSS kludge would work.

OK. Since the fluids supported by GDSS (hydrazine and Xenon) are not used by Starship HLS, I suspect that Starship HLS will implement IDSS and interoperate properly with Gateway. If Starship HLS must be designed to mate directly with Orion (i.e., if Gateway is not available in time for Artemis III) then HLS will not be transferring fluids to to from Orion and an IDSS interface suffices.

IIRC, GDSS supports a much higher bandwidth network connection.  Not the end of the world if LSS can't use that, but kinda nice to have.  I can't remember if it's a second umbilical or somehow upward-compatible with the existing IDSS.

HOWEVER: the HLS IDSS port must be active/passive, not just active-only, in order to interface with Orion, which I assume is active-only, and with Gateway, which is passive-only. This is not a new requirement added for the SLS/Orion replacement.  Dragon is active-only.

Well... I'm pretty sure the SLD specs actually allow the use of an "active-active mating adapter".  The idea is that you have a passive-only HLS, but it's launched with the AAMA on its nose.  So you've got HLS-passiveIDA-AAMA(consisting of two active IDA's back-to-back, or one active IDA and one active GDA)-passiveGDA-Gateway.  When the HLS departs for the lunar surface, it leaves the AAMA on the Gateway.  When it returns, the Gateway+AAMA is the active side for the passive HLS's IDA.

This is... weird, and kinda stupid, because you have the maneuvering element as the passive side, but if either provider had trouble developing full active/passive, it's a possibility.

__________
¹For the hardcore docking nerds, note that I'm casually (and incorrectly) using the term "IDA" as shorthand for "some kind of IDSS implementation".  Same thing for "GDA" as "some kind of GDSS implementation".

[TheRadicalModerate]

So what is the minimal modification to Artemis to fix this?

Congress.

True for a minimal modification for Artemis.  But if SpaceX wants to put a private crew of four on the lunar surface, Congress just has to sit there looking embarrassed and ashamed.  (Shame is a very high bar.  Embarrassment, a bit lower.)

It's a pretty expensive private mission, though--unless SpaceX can resurrect the 7-seater D2 configuration, which I think is now very hard.

[DanClemmensen]

So what is the minimal modification to Artemis to fix this?

Congress.

True for a minimal modification for Artemis.  But if SpaceX wants to put a private crew of four on the lunar surface, Congress just has to sit there looking embarrassed and ashamed.  (Shame is a very high bar.  Embarrassment, a bit lower.)

It's a pretty expensive private mission, though--unless SpaceX can resurrect the 7-seater D2 configuration, which I think is now very hard.

If SpaceX or anyone else flys a CLD as a standalone non-Artemis system, then things change somewhat. Customers can go to the CLD, which can accumulate a crew of up to 20 to go on a lunar excursion. OTV and HLS take the entire 20 on the excursion and return them to the CLD.

[AnalogMan]

Remember, IDSS only represents docking to the International Space Station.  GDSS is the standard for docking to the gateway, and they are not interchangeable for more than an emergency. 

Dragon, CST-100 = IDSS
Orion, HLS = GDSS

They cannot be made interchangeable.  and modifying one to be the other will come with a cost.

Just something to keep in mind as you combine options.

This is not quite correct.

Per GLS-RQMT-001 (the Gateway Logistics Services Requirements, attached below), the Gateway Docking System (GDS) is an IDSS-compatible design, with additional fluid (for refueling the Gateway), electrical, data, and possibly other connections, this compatibility implies that the rest of the docking system's IDSS required parts are not changed. Keep-out zones for such connections are reserved in the current revision (Rev F, July 2022) of the IDSS. Basically, GDSS is a specialized type of IDSS.

An IDSS compliant docking system should be able to dock with the Gateway, but it won't be able to use those other connections. A GDS should likewise be able to dock to the ISS.

The NASA Docking System Block 2 is the NASA developed GDSS-compatible docking system for Orion.

NASA's requirements for Gateway docking systems are specified in DSG-SPEC-MECH-017, Gateway Docking System Specification (GDSS), but unfortunately for us, this document is not publicly available.

There is a draft initial release version of DSG-SPEC-MECH-017 approved for public release (dated June 30, 2019) which I have attached.

[DanClemmensen]

There is a draft initial release version of DSG-SPEC-MECH-017 approved for public release (dated June 30, 2019) which I have attached.

Thanks!
As I read it, unless there was a radical change after this draft, GDSS passive ports on Gateway will interoperate with active IDSS ports on visiting spacecraft.

The very first section says:

1.0 INTRODUCTION
This Gateway Docking System Specification (GDSS) document represents the implementation
of the International Docking System Standard (IDSS) Interface Definition Document (IDD) for
the Gateway program. It establishes a common docking interface to support the assembly and
operation of Gateway, ensuring successful integration of Gateway elements and visiting
vehicles.

The rest of the document references document IDSS IDD about 100 times, and I did not immediately notice anything that precludes interoperability.

[CraigLieb]

NASA created competing private contractor teams to return us to launching astronauts to the space station. How about an insurance policy as a firm fixed-price contract backup to SLS paying someone to certify and launch astronauts privately to the moon? It could bring Starship and any other competing contractors that qualify into competition for the role with a proposed 5 launch package. It could be funded with the price of one SLS test launch (4Billion?). The SLS program continues along a parallel path and if this fails, it maybe matures commercial space a little in the mean time.
I apologize if this duplicates or overlaps with upthread posts and proposals, as I failed to read the whole thread in detail before posting this.

[DanClemmensen]

NASA created competing private contractor teams to return us to launching astronauts to the space station. How about an insurance policy as a firm fixed-price contract backup to SLS paying someone to certify and launch astronauts privately to the moon? It could bring Starship and any other competing contractors that qualify into competition for the role with a proposed 5 launch package. It could be funded with the price of one SLS test launch (4Billion?). The SLS program continues along a parallel path and if this fails, it maybe matures commercial space a little in the mean time.
I apologize if this duplicates or overlaps with upthread posts and proposals, as I failed to read the whole thread in detail before posting this.

Good idea. This thread was created in response to a "what if" question: how to salvage Artemis if congressional budget cutters kill SLS/Orion? If instead NASA (or elements inside congress) pitch it as an insurance policy, it might be a less unpalatable way to ease it in prior to an actual SLS/Orion cancellation.

I don't think SpaceX could bid this for less than about $3 Billion for the development plus one mission, or for less than about $1.5 Billion for each subsequent mission. My GUESS is that other bidders would have no chance, since I think they need a lot more new hardware. This probably means NASA would not be able to award their cherished multiple bids, putting them in the same situation as the first HLS award.

[Jim]

NASA created competing private contractor teams to return us to launching astronauts to the space station.

NASA created no teams.   NASA just put out RFPs or equivalents.

[deltaV]

This thread is in the SpaceX section so IMO it should be limited to how SpaceX hardware could do the missions. Discussions about how NASA could structure procurements for a non-SLS Artemis program belong in the "Heavy Lift Launch Vehicle (HLV/SLS)", "Missions To The Moon (HSF)", or "Space Policy" sections of the forum.