SpaceX - US Deorbit Vehicle (for ISS)

[spacebleachers]

My guess: no fairing. It's a one-off and the top is a Dragon capsule, so it's already most of the way toward not needing a fairing. A fairing would add cost. By contrast, Vast has no need to be designed for a no-fairing launch abort, so a fairing makes sense for it.

If the vehicle is ~13 m tall and the panels fold flat it should fit inside an extended fairing and cost should be minimal, as they should have successfully recovered and refurbished them by 2028-29. There's also the possibly that it will launch inside Starship as SpaceX only mentioned it would fly on 'heavy' launch vehicle and didn't specify FH.



If Falcon Heavy can put 63.8 tons into LEO, could this mission fly fully reusable?

It should be noted that during the press conference it was stated that NASA LSP will be determining the launch vehicle and not SpaceX. While FH makes total sense, by the time a decision is required Vulcan and probably New Glenn will be available. They don’t currently fly Dragons on FH as was stated upthread, but the case could be made that it will be a lot easier to validate FH for the launch than one of the others.

[DanClemmensen]

My guess: no fairing. It's a one-off and the top is a Dragon capsule, so it's already most of the way toward not needing a fairing. A fairing would add cost.

The starlink solar panels will need some form of fairing

You are right and my guess was probably wrong. Also, because NASA is buying the launch separately, SpaceX has no reason to consider the cost of the fairings, and actually have an incentive to use fairings, since they will increase the value of the launch for which they will be bidding separately. This assumes that SpaceX thinks FH will be competitive at the time of the LV bid (2027?) or that Starship-cargo will be operational by then.

[meekGee]

If starship is at play, wouldn't a tanker have enough propellant to do this, as-is?

[DanClemmensen]

If starship is at play, wouldn't a tanker have enough propellant to do this, as-is?

Starship is no longer at play as the USDV itself. It may or may not be a contender as an LV to deliver the USDV. I think this would be a "standard" cargo version of Starship, No tanker needed.

[meekGee]

If starship is at play, wouldn't a tanker have enough propellant to do this, as-is?

Starship is no longer at play as the USDV itself. It may or may not be a contender as an LV to deliver the USDV. I think this would be a "standard" cargo version of Starship, No tanker needed.

I know, but was wondering if it's at play for delivering the USDV, why can't they get the option for delivering nothing and just doing the work with the vehicle that delivered the nothing.

It's not like the mission is happening tomorrow...

[DanClemmensen]

If starship is at play, wouldn't a tanker have enough propellant to do this, as-is?

Starship is no longer at play as the USDV itself. It may or may not be a contender as an LV to deliver the USDV. I think this would be a "standard" cargo version of Starship, No tanker needed.

I know, but was wondering if it's at play for delivering the USDV, why can't they get the option for delivering nothing and just doing the work with the vehicle that delivered the nothing.

It's not like the mission is happening tomorrow...

Tanker cannot meet the USDV requirements. Most critically, it cannot dock to Harmony forward and push at 10,000 N. No IDSS port, and Raptors cannot throttle down that far. If you push too hard, you will break something. Tanker's RCS prpbably cannot push hard enough to do the job.

[Jim]

but the case could be made that it will be a lot easier to validate FH for the launch than one of the others.

not really

[Jim]

It's not like the mission is happening tomorrow...

Its not like Starship will be ready as long term spacecraft

The mission is for a year to a year and half.  Starship has no low thrust thrusters.  Starship configuration and IOC keeps changing.  It doesn't matter for HLS but this has to be ready per schedule.

[DanClemmensen]

It's not like the mission is happening tomorrow...

Its not like Starship will be ready as long term spacecraft

The mission is for a year to a year and half.  Starship has no low thrust thrusters.  Starship configuration and IOC keeps changing.  It doesn't matter for HLS but this has to be ready per schedule.

Even if a Starship derivative were technically feasible, It would require a different type of contract. The existing contract is a purchase of a vehicle by NASA that NASA will own and operate, and NASA is responsible to contract for someone to launch it. If they picked a Starship derivative, they would in essence also be picking the launch vehicle. If instead NASA had contracted for the service of de-orbiting ISS, then SpaceX could have bid Starship. NASA might well have rejected Starship as too risky for several reasons.

Of course, if NASA had asked for a service, they might not have gotten any bidders, because of the liability issues. With the current contract, NASA is the responsible party.

[woods170]

Since some people were asking me privately, I relayed a question regarding the number of Draco engines to my SpaceX sources. What I got back is basically this:

There will be the normal 16 Draco thrusters on the capsule part of the USDV. No changes to the RCS layout on the capsule part.

The newly built deorbit propellant and propulsion section will sport 46 Draco thrusters:
- 16 Dracos for attitude control. As correctly shown in the released artist's impression, they are located in 8 pairs of two around the circumference of the aft end of the deorbit section.
- 30 Dracos for the deorbit burns. As correctly shown in the artist's impression, all 30 of those Dracos are pointing "backwards" and are mounted in a circle at the backside of the deorbit section. No gimballing. Attitude control during the deorbit burns is done solely by the 32 attitude control Dracos (16 on the capsule and 16 on the deorbit section).

The USDV therefor sports a grand total of not 46, but 62 Draco thrusters: the normal 16 on the capsule part and 46 on the deorbit section.

What was clarified further to me is that the capsule part will retain its own set of propellant tanks, which will feed the 16 Draco thrusters on the capsule. So, no changes to how the RSC and orbit control work on the capsule part, EXCEPT for the flight control software, which now also controls all the thrusters in the deorbit section.

The 46 Draco thrusters on the deorbit section will feed off a separate set of propellant tanks mounted in the deorbit section.
As I understood it NO new tanks are being developed for this: the current production line for Cargo Dragon/Crew Dragon propellant tanks will supply an unspecified number of tanks of the existing design.

Further: as on a "normal" Cargo Dragon/Crew Dragon vehicle, the thermal control system radiators are mounted on the deorbit section.

I was further given some information which I am, at this time, not at liberty to disclose. Best I can say is that it relates to an "experimental phase" proposed to NASA by SpaceX, but which has not been OK-ed by NASA (yet). Two clues to the nature of this experiment are visible in the artist's impression released by SpaceX and NASA.

[StraumliBlight]

I was further given some information which I am, at this time, not at liberty to disclose. Best I can say is that it relates to an "experimental phase" proposed to NASA by SpaceX, but which has not been OK-ed by NASA (yet). Two clues to the nature of this experiment are visible in the artist's impression released by SpaceX and NASA.

The Dragon in the render has a heat shield and a trunk release mechanism, NASA also mentioned in the teleconference that it would be nice if there was down mass available to recover some mementoes. So capsule recovery would be my first guess.

The second observation is that the side RCS thrusters are flush to the trunk, instead of arranged externally like Dragon XL, this may indicate SpaceX want to launch it without a fairing.

It would be cool There could be useful science data collected by externally filming the re-entry and break up of the ISS, preferably in IMAX format and using multiple Starlink antennas. A detached trunk might be able to fulfil this role, though the current RCS thrusters layout would probably prevent manoeuvring independently.

[matthewkantar]

I imagine the ground testing of this rig will be interesting. Will they do a full duration static fire of the thirty engine trunk?

[rsnellenberger]

I suppose that SpaceX still has the old Dragon 1 solar array/radiator/fairing designs laying around that they could use for this vehicle...

[zubenelgenubi]

[It would be cool] There could be useful science data collected by externally filming the re-entry and break up of the ISS, preferably in IMAX format and using multiple Starlink antennas. A detached trunk might be able to fulfil this role, though the current RCS thrusters layout would probably prevent manoeuvring independently.

A final ISS-focused IMAX film is a great idea.
Space Station 3D
A Beautiful Planet 3D
 🎥 🎞 🎦 🎬 📽 👌 💡

[DanClemmensen]

This part was bugging me (as the 4 forward bulkhead thrusters are inhibited when close to the station) and are basically obstructed when docked. So really only 12 thrusters on cargo dragon are available for control.

I think those thrusters are used during the rendezvous and docking phase, so just leaving them there will simplify and de-risk the changes needed to the docking software.

If they intend to re-purpose an  existing Cargo Dragon capsule instead of building a new one, then it's easier to just leave them there even if they did not need to actually use them.

[Jim]

I imagine the ground testing of this rig will be interesting. Will they do a full duration static fire of the thirty engine trunk?

nah.  Spacecraft don't do static fires

[Jim]

Attitude control during the deorbit burns is done solely by the 32 attitude control Dracos (16 on the capsule and 16 on the deorbit section).

Meaning the Russian segment thrusters and ISS CMG's are not used

[jarmumd]

But looking at the render more closely (and simulating different views with DOUG), it doesn't look like the IDA adapter is rendered.
...

I can't believe that I'm asking this, but is SpaceX proposing an APAS-95 dragon?

There is no world in which that makes sense.  What does make sense is that whomever made the graphic put the USDV in the wrong place.  And if you think that the animators don't make mistakes, I remember the docking team having a collective panic attack when the first graphics of Dragon 2 and ISS came out, because the docking adapter was rotated 180, and we were all worried we missed something so fundamental.

[StraumliBlight]

Assuming the Trunk diameter is 3.6 m:

 • Trunk height: 6.4 m.
 • Draco engine nozzle: ~0.26 m diameter x 0.23 m long.
 • Solar array: ~6.4 m x 3.1 m (in 9 fold out panels)

[Nomadd]

Attitude control during the deorbit burns is done solely by the 32 attitude control Dracos (16 on the capsule and 16 on the deorbit section).

Meaning the Russian segment thrusters and ISS CMG's are not used

It was mentioned right after "No gimballing" for the main 30 deorbit thrusters.