SpaceX - US Deorbit Vehicle (for ISS)

[FutureSpaceTourist]

This thread is for updates and discussion of the modified Dragon chosen by NASA for de-orbiting the ISS.

There is a separate thread for NASA’s procurement of the vehicle: https://forum.nasaspaceflight.com/index.php?topic=56996.0



https://twitter.com/sciguyspace/status/1806762777333076064

Bill Spetch, operations integration manager for NASA’s International Space Station Program, confirms that the US Deorbit Vehicle will be based on "Dragon heritage" hardware. It will involve modifications of the trunk.

[Nomadd]

 If they're going to need 7-8 tons of fuel, would it be a Heavy launch?

[Remes]

At 50:00:
Eric Berger: What is the architecture for usdv, will it be a modified dragon, a dragon xl, or something else?
Bill Spetch: that's based on dragon heritage design. They have do some modifications and some changes to the trunk.

• Bill Spetch, operations integration manager, NASA’s International Space Station Program

[Jim]

If they're going to need 7-8 tons of fuel, would it be a Heavy launch?

Closer to 15

[matthewkantar]

Could it be that it will take more than one launch? 

[vaporcobra]

If they're going to need 7-8 tons of fuel, would it be a Heavy launch?

Closer to 15

Welp, definitely a Falcon Heavy mission or maybe a fully expendable F9 if it needs ~15 tons of fuel and the usual ~9 tons of dry mass!

And if SpaceX plans on daisy-chaining existing Dragon 2 propellant COPVs to add that capacity, 15 tons would imply ~30 extra COPVs in the trunk in addition to the capsule's usual 8. Plenty doable with the roughly 4m x 3.5m available.

[FutureSpaceTourist]

It’s not very SpaceX-like to do a one-off project that doesn’t also support/contribute to other missions or tech development goals.

So was this modified Dragon also part of the Polaris program’s study for servicing Hubble? Maybe also with an eye on commercial space stations in development and/or propellant depots?

Or is SpaceX just doing the ISS de-orbit vehicle to support their biggest customer?

Edit to add:

SpaceX first approached NASA about possible Hubble mission in Spring/Summer 2022 and the ISS de-orbit RFI was issued in August 2022.

[Remes]

Polaris is a manned mission. I believe the usdv will be unmanned and maximize fuel/thruster/redundancy payload. More like Soyuz vs Progress.

In addition to one off and no future use: I believe the plan of SpaceX was to replace F9 et al with SS/SH. Albeit I believe having a smaller vehicle would make sense, because a coach with only 5 passengers is not lucrative. But then again having 2 launch systems... So SpaceX will have to deal with Dragon longer and then even in a special variant.

Other reasons to do it:
- It is good money.
- It is high profile PR.
- The project has to start now. There is only one provider with a proven and available vehicle which comes close to be doing it. So if you are the only one capable, if it has to be done, and you let down your nation's space program, then a whole bunch of people (at NASA and politics) will never forget that.

[Remes]

The ISS has 450t and the "SSP 51101 USDV SRD" requires 57m/s.

p = 57 m/s * 450000kg = 25.65M kg*m/s

Taking the Draco Isp with 2300m/s that is a required propellant mass

m = t*F/Isp = 11140kg

Super Draco has 73kN Thrust. Requirement is a minimum of 3236N (Soyuz/Progress have 2.95kN). Also I don't know, if a Super Draco is designed for such long burn times.

With one Super Draco burn time would be

t=p/F=351s

And with a speed of 7.8km/s that is somewhere around 2700km ground distance.

NTO is about 1.4t/m³ and MMH 0.875t/m3. So guessing 11t is about 11m³ and Dragon trunk having 37m³ it might fit into it. Now that is all without tanks, pressurization, plumbing, ... Redundancy will take some weight and extra fuel.

Dragon has 6t payload mass. If the existing dracos are removed, life support, ... a little more. So sounds to me like we are talking about a Dragon+F9 Heavy+strengthened trunk. Not sure if the Super Draco is an option, but I'm not aware of any alternatives available from SpaceX. Maybe they buy some existing smaller engines with proven track record? They anyway most likely want to have several thrusters for redundancy reasons. So a super draco placed in the middle of the trunk is most likely out. (I'm not up to date with SS/SH hot gas thrusters? Anythhing there with ~800N? 4 of them would fulfill the requiremens and provide redundancy).

[steveleach]

The ISS has 450t and the "SSP 51101 USDV SRD" requires 57m/s.

p = 57 m/s * 450000kg = 25.65M kg*m/s

Taking the Draco Isp with 2300m/s that is a required propellant mass

m = t*F/Isp = 11140kg

Super Draco has 73kN Thrust. Requirement is a minimum of 3236N (Soyuz/Progress have 2.95kN). Also I don't know, if a Super Draco is designed for such long burn times.

With one Super Draco burn time would be

t=p/F=351s

And with a speed of 7.8km/s that is somewhere around 2700km ground distance.

NTO is about 1.4t/m³ and MMH 0.875t/m3. So guessing 11t is about 11m³ and Dragon trunk having 37m³ it might fit into it. Now that is all without tanks, pressurization, plumbing, ... Redundancy will take some weight and extra fuel.

Dragon has 6t payload mass. If the existing dracos are removed, life support, ... a little more. So sounds to me like we are talking about a Dragon+F9 Heavy+strengthened trunk. Not sure if the Super Draco is an option, but I'm not aware of any alternatives available from SpaceX. Maybe they buy some existing smaller engines with proven track record? They anyway most likely want to have several thrusters for redundancy reasons. So a super draco placed in the middle of the trunk is most likely out. (I'm not up to date with SS/SH hot gas thrusters? Anythhing there with ~800N? 4 of them would fulfill the requiremens and provide redundancy).

Why wouldn't they just use 8 Dracos?

[vaporcobra]

It’s not very SpaceX-like to do a one-off project that doesn’t also support/contribute to other missions or tech development goals.

So was this modified Dragon also part of the Polaris program’s study for servicing Hubble? Maybe also with an eye on commercial space stations in development and/or propellant depots?

Or is SpaceX just doing the ISS de-orbit vehicle to support their biggest customer?

I was wondering the same thing. It seems unlikely that this modified Dragon concept popped out of nowhere just for the deorbit vehicle, especially given that (per an Eric Berger source) SpaceX may not have even bid on the first RFP. The contract value is also strange in that context: $843M is almost a quarter of the value (in 2024 $s) of SpaceX's initial 2014 contract to complete most Crew Dragon R&D, build half a dozen flight vehicles, and complete two major abort tests, two orbital test flights, and six operational missions!

That just seems at odds with the implication that it's more of a modified Dragon 2 than a bespoke spacecraft. So many possibilities, but my current best guess is that SpaceX will be building an all-new Dragon 2 (rather than modifying an old reused capsule) with substantial changes that borrow from concepts/designs meant for Dragon XL's propulsion section and whatever Crew Dragon tweaks it proposed for the Hubble reboost mission.

Maybe SpaceX is also thinking about ways to keep Dragon highly relevant and grow the markets it can access well into the 2030s? A Dragon w/ more dV could be useful for future destinations and maybe help increase SpaceX's tourism market by enabling service to more orbits/inclinations and providing more utility (orbit raising, mobility augmentation, etc) to entice private station customers. Maybe it could even outright supersede a bespoke Dragon XL and allow SpaceX to avoid that particular dead-end.

[ugordan]

Maybe SpaceX is also thinking about ways to keep Dragon highly relevant and grow the markets it can access well into the 2030s? A Dragon w/ more dV could be useful for future destinations and maybe help increase SpaceX's tourism market by enabling service to more orbits/inclinations and providing more utility (orbit raising, mobility augmentation, etc) to entice private station customers. Maybe it could even outright supersede a bespoke Dragon XL and allow SpaceX to avoid that particular dead-end.

Wouldn't that necessitate human-rating the FH as well? This deorbit vehicle will need many extra tonnes of prop (Jim says closer to 15) which is likely to be outside of reach for even an expendable single-stick F9.
Unless they make the whole thing more modular like fewer prop tanks for these future destinations that don't really require the oomph it takes to deorbit the behemoth that is the ISS?

[Remes]

Why wouldn't they just use 8 Dracos?

Are they qualified for a 30min burn? On youtube "Draco Thruster Vacuum Firing" shows a 10min burn. I wasn't aware of that. So might indeed be an option.

(And I'm sure SpaceX is happy not giving up their vertical integration and avoiding the contractual hazzle of outsourcing critical parts.)

Wouldn't that necessitate human-rating the FH as well?

I don't think usdv will be manned. Once it is seperated FH plays no role any more.
It's a little bit like Shuttle-Centaur. Astronauts might not be amused riding on so much fuel and so much plumbing.

[baldusi]

It’s not very SpaceX-like to do a one-off project that doesn’t also support/contribute to other missions or tech development goals.

So was this modified Dragon also part of the Polaris program’s study for servicing Hubble? Maybe also with an eye on commercial space stations in development and/or propellant depots?

Or is SpaceX just doing the ISS de-orbit vehicle to support their biggest customer?

I was wondering the same thing. It seems unlikely that this modified Dragon concept popped out of nowhere just for the deorbit vehicle, especially given that (per an Eric Berger source) SpaceX may not have even bid on the first RFP. The contract value is also strange in that context: $843M is almost a quarter of the value (in 2024 $s) of SpaceX's initial 2014 contract to complete most Crew Dragon R&D, build half a dozen flight vehicles, and complete two major abort tests, two orbital test flights, and six operational missions!

That just seems at odds with the implication that it's more of a modified Dragon 2 than a bespoke spacecraft. So many possibilities, but my current best guess is that SpaceX will be building an all-new Dragon 2 (rather than modifying an old reused capsule) with substantial changes that borrow from concepts/designs meant for Dragon XL's propulsion section and whatever Crew Dragon tweaks it proposed for the Hubble reboost mission.

Maybe SpaceX is also thinking about ways to keep Dragon highly relevant and grow the markets it can access well into the 2030s? A Dragon w/ more dV could be useful for future destinations and maybe help increase SpaceX's tourism market by enabling service to more orbits/inclinations and providing more utility (orbit raising, mobility augmentation, etc) to entice private station customers. Maybe it could even outright supersede a bespoke Dragon XL and allow SpaceX to avoid that particular dead-end.

One important contracting detail is that this will be a NASA vehicle and a NASA mission, not a service mission. Since NASA will have spaceship (and possibly design) ownership, costs have to count with NASA making the decisions and doing a full FAR 15 accounting. I assume this is very expensive but given the ridiculous amount of potential liabilities, it's the only way that any al the parties would be willing to accept the risk.

[geza]

It’s not very SpaceX-like to do a one-off project that doesn’t also support/contribute to other missions or tech development goals.

What if this development is coupled to a future SpaceX offer for Mars Sample Return? Imagine a modified Dragon with beefed up propulsion for a direct return to Earth. It should be delivered to the Martian surface by a Starship.

Cargo Starship to Mars is in the plans, anyway. If Starship-HLS for 2026 is serious, then cargo landing on Mars should be achievable in the '27, or in '29, at the latest, in time for MSR. Then a return spacecraft is needed. If it is a high-deltaV Dragon, then has a high commonality with the ISS-terminator. Having generous NASA money for both will help a lot. Both spacecraft are needed around the same time.

[DanClemmensen]

Would SpaceX consider a literal modified Dragon? They currently have four Crew Dragons and one being built. By the time USDV is needed, the demand for Crew Dragon flights will be going away, almost by definition, so SpaceX may be able to modify one of the existing Crew Dragon Capsules. It is especially true if Starliner is flying: NASA is committed to fly six Starliner missions and time is getting short, so Starliner could fly the last two crewed ISS missions.

More or less the same is true for Cargo Dragon if it is a better starting point: modify one of the three active Cargo Dragons and let Cygnus pick up the last resupply missions if needed.

[StraumliBlight]

Does the deorbit vehicle need to be expended?

Or to rephrase the question, could a standard Cargo Dragon be used and limit the modifications to an extended trunk with an engine? Once the ISS altitude has been lowered sufficiently it could undock and perform a normal re-entry and recovery.

[DanClemmensen]

Does the deorbit vehicle need to be expended?

Or to rephrase the question, could a standard Cargo Dragon be used and limit the modifications to an extended trunk with an engine? Once the ISS altitude has been lowered sufficiently it could undock and perform a normal re-entry and recovery.

Jim tersely said "no" much earlier in the thread. After reading the CONOPS paper recently, I think I understand why. The whole object of this excersize is to hit a very precise small area with extreme reliability, so the USDV must be able to make late corrections if necessary.

My opinion:
Separately, that Cargo (or Crew) Dragon will have very limited value if recovered, because its main customer, ISS, will be gone, the number of remaining customers, if any, will be small. The remaining Dragon fleet will likely be more than adequate. Thus, the cost of the extra design and production effort to retain recoverability is not likely to be (ahem) recovered.

[greybeardengineer]

Or is SpaceX just doing the ISS de-orbit vehicle to support their biggest customer?

SpaceX will be paid >$800m to do something 1) well within their competency, 2) likely costs them *way* less than $800m to do the NRE and build/launch the hardware, 3) does a vital task for NASA, a critical customer, that apparently had no other takers.

Seems like a no-brainer to me.

[DanClemmensen]

Or is SpaceX just doing the ISS de-orbit vehicle to support their biggest customer?

SpaceX will be paid >$800m to do something 1) well within their competency, 2) likely costs them *way* less than $800m to do the NRE and build/launch the hardware, 3) does a vital task for NASA, a critical customer, that apparently had no other takers.

Seems like a no-brainer to me.

The only issue would be the opportunity costs of diverting the engineers and other resources from more strategic tasks. I have zero insight into this, but presumably the $834 million will cover it.

[Jorge]

My predictions (completely uninformed about what SpaceX actually bid, but somewhat informed on the USDV requirements):

1) The outer moldline will much more closely resemble Dragon XL (i.e. cylindrical) than Dragon 2. No capsule, no heat shield, no pressurized volume (other than possibly for avionics), all replaced by propellant tanks. (I'll add, if it turns out *not* to be cylindrical, that will be purely for ascent aero reasons, i.e. to prevent having to add a fairing.)
2) Clustered Draco for deorbit propulsion. No Super Draco. Would be extremely bad form to break parts off ISS during the deorbit burn.

[Bananas_on_Mars]

Can it be ruled out that they‘re planning to use a subcontractor for part of the mission?

Impulse Space might have a suitable thruster with Rigel and using storable propellants.

Most of the „CLPS“ companies should have thrusters that are in a thrust range between Draco and Super Draco, suitable for continuous firing over several minutes.

[DanClemmensen]

My predictions (completely uninformed about what SpaceX actually bid, but somewhat informed on the USDV requirements):

1) The outer moldline will much more closely resemble Dragon XL (i.e. cylindrical) than Dragon 2. No capsule, no heat shield, no pressurized volume (other than possibly for avionics), all replaced by propellant tanks. (I'll add, if it turns out *not* to be cylindrical, that will be purely for ascent aero reasons, i.e. to prevent having to add a fairing.)
2) Clustered Draco for deorbit propulsion. No Super Draco. Would be extremely bad form to break parts off ISS during the deorbit burn.

So more like Dragon XL in many ways, but with all cargo space converted into fuel and thrusters. Great if they can reuse many of the design elements.

[Jim]

I don't think usdv will be manned. Once it is seperated FH plays no role any more.
It's a little bit like Shuttle-Centaur. Astronauts might not be amused riding on so much fuel and so much plumbing.

Huh? The shuttle had a similar amount of propellant.  Apollo CSM had a quarter more.

[Remes]

I don't think usdv will be manned. Once it is seperated FH plays no role any more.
It's a little bit like Shuttle-Centaur. Astronauts might not be amused riding on so much fuel and so much plumbing.

Huh? The shuttle had a similar amount of propellant.  Apollo CSM had a quarter more.

I'm refering to the opinions of the astronauts and engineers which were working on that. I don't remember where I read it originally, but googling for "Space Shuttle Death Star" does show enough articles. The problem was not to add more propellant. It's about adding tanks, valves, plumbing, ... a whole bunch of additional failure points which are not there in a standard vehicle.

[Jim]

I'm refering to the opinions of the astronauts and engineers which were working on that. I don't remember where I read it originally, but googling for "Space Shuttle Death Star" does show enough articles. The problem was not to add more propellant. It's about adding tanks, valves, plumbing, ... a whole bunch of additional failure points which are not there in a standard vehicle.

No, it wasn't "adding tanks, valves, plumbing".  It was specific to Shuttle Centaur.  It was an issue because of LH2 and balloon tanks. 
The shuttle flew often with more "tanks, valves, plumbing"
The shuttle use to fly with 3 to 4 spacecraft with separate hypergolic propellant systems and solid motors with S&As. 
Or missions with IUS which had two large SRMs and a hydrazine system with a spacecraft and its hypergolic propulsion system

[Thorny]

No, it wasn't "adding tanks, valves, plumbing".  It was specific to Shuttle Centaur.  It was an issue because of LH2 and balloon tanks. 
The shuttle flew often with more "tanks, valves, plumbing"
The shuttle use to fly with 3 to 4 spacecraft with separate hypergolic propellant systems and solid motors with S&As. 
Or missions with IUS which had two larger SRMs and a hydrazine system with a spacecraft and its propulsion system

Also the EDO pallet.

[Jim]

This thread is for updates and discussion of the modified Dragon chosen by NASA for de-orbiting the ISS.

The thread title should be what it is called:  US Deorbit Vehicle and not modified Dragon

[Jim]

It’s not very SpaceX-like to do a one-off project that doesn’t also support/contribute to other missions or tech development goals.

So was this modified Dragon also part of the Polaris program’s study for servicing Hubble? Maybe also with an eye on commercial space stations in development and/or propellant depots?

Or is SpaceX just doing the ISS de-orbit vehicle to support their biggest customer?

I was wondering the same thing. It seems unlikely that this modified Dragon concept popped out of nowhere just for the deorbit vehicle, especially given that (per an Eric Berger source) SpaceX may not have even bid on the first RFP. The contract value is also strange in that context: $843M is almost a quarter of the value (in 2024 $s) of SpaceX's initial 2014 contract to complete most Crew Dragon R&D, build half a dozen flight vehicles, and complete two major abort tests, two orbital test flights, and six operational missions!

That just seems at odds with the implication that it's more of a modified Dragon 2 than a bespoke spacecraft. So many possibilities, but my current best guess is that SpaceX will be building an all-new Dragon 2 (rather than modifying an old reused capsule) with substantial changes that borrow from concepts/designs meant for Dragon XL's propulsion section and whatever Crew Dragon tweaks it proposed for the Hubble reboost mission.

Maybe SpaceX is also thinking about ways to keep Dragon highly relevant and grow the markets it can access well into the 2030s? A Dragon w/ more dV could be useful for future destinations and maybe help increase SpaceX's tourism market by enabling service to more orbits/inclinations and providing more utility (orbit raising, mobility augmentation, etc) to entice private station customers. Maybe it could even outright supersede a bespoke Dragon XL and allow SpaceX to avoid that particular dead-end.

it is a one off

[jarmumd]

Would SpaceX consider a literal modified Dragon? They currently have four Crew Dragons and one being built. By the time USDV is needed, the demand for Crew Dragon flights will be going away, almost by definition, so SpaceX may be able to modify one of the existing Crew Dragon Capsules. It is especially true if Starliner is flying: NASA is committed to fly six Starliner missions and time is getting short, so Starliner could fly the last two crewed ISS missions.

More or less the same is true for Cargo Dragon if it is a better starting point: modify one of the three active Cargo Dragons and let Cygnus pick up the last resupply missions if needed.

This would make a lot of sense to me.  I've always heard that Elon wants to transition to the new tech as soon as possible (ie starship), so he's not going to be looking at Dragon 2 with much fondness.

I agree with you.  Path of least resistance is taking an existing cargo vehicle (no dev work on RPOD), make one-off modifications with the module and trunk, whole thing goes in the ocean with ISS.  Might even consider putting Dragon in a FH fairing so you don't have to do new aero - doesn't need abort capability (assuming the stack would fit).  Could easily punch holes through the heat shield for tanks/plumbing since you don't care about a pressure vessel anymore.

[StraumliBlight]

USDV Source Selection Statement

I have reviewed all the evaluation findings and have concluded:
 • SpaceX has the highest Mission Suitability score, the highest Past Performance Rating, and a significantly lower Total Evaluated Price.
 • NG has the lowest Mission Suitability score/ratings, the lower Past Performance Rating, and a significantly higher Total Evaluated Probable Cost/Price.

While both Offerors provide Strengths in their proposals, only SpaceX’s proposal offers Significant Strengths. The Weakness identified in SpaceX’s proposal relates to potential risk to schedule, and based on the specific nature of this Weakness, I find that the concerns can be addressed and resolved during routine contract administration. NG’s seven Weaknesses create both technical and schedule risks, that when viewed wholistically, impact reliability and increase risk of successful contract performance. I have examined and concur with the SEB’s evaluation of proposals and recommendations. My independent analysis finds value to NASA in SpaceX’s superior Mission Suitability, higher Past Performance rating, and significantly lower priced proposal.

Summary:
 • SpaceX design "reuses flight-proven hardware and software designs, and uses flight-proven component designs for the newly designed vehicle section,". Also "including the reuse of a flight-proven vehicle" implies an existing Dragon will be modified.
 • Desired delivery date: August 1, 2028, required delivery date: May 1, 2029.
 • NG’s Total Evaluated Price was "significantly higher" than SpaceX’s ($680M).
 • AlphaSpaces’ bid was rejected in March 2024.

[StraumliBlight]

NASA to Provide Background on Space Station Deorbit Planning

NASA is planning for the future in low Earth orbit for science, research, and commercial opportunities as the agency and its international partners maximize the use of the International Space Station.

As the agency fosters new commercial space stations, leadership from NASA and SpaceX will participate in a media teleconference at 2 p.m. EDT Wednesday, July 17, to discuss the company’s selection to develop and deliver the U.S. Deorbit Vehicle, which will safely move the International Space Station out of orbit and into a remote area of an ocean at the end of its operations.

Audio of the teleconference will stream live on the agency’s website:

   https://www.nasa.gov/nasatv

Participants include:
 • Ken Bowersox, associate administrator, NASA’s Space Operations Mission Directorate
 • Dana Weigel, manager, NASA’s International Space Station Program
 • Sarah Walker, director, Dragon mission management, SpaceX

Media interested in participating must contact the newsroom at NASA Johnson no later than one hour prior to the start of the call at 281-483-5111 or [email protected]. A copy of NASA’s media accreditation policy is online.

As the agency transitions to commercially owned space destinations, it is crucial to prepare for the safe and responsible deorbit of the space station in a controlled manner after the end of its operational life in 2030.

[FutureSpaceTourist]

https://twitter.com/spacex/status/1813632705281818671

With 6x more propellant and 4x the power of today’s Dragon spacecraft, SpaceX was selected to design and develop the U.S. Deorbit Vehicle for a precise, controlled deorbit of the @Space_Station

[StraumliBlight]

[StraumliBlight]

Some details from the teleconference:
 • Built on an existing Cargo Dragon.
 • Enhanced Trunk section has 30 Draco engines and can produce 10,000 N thrust.
 • 22-26 engines can fire at the same time.
 • Will have 16 tons of propellent and require a Falcon Heavy launch.
 • Total vehicle mass ~30 tons.
 • Trunk is twice the height of a standard trunk.
 • Currently no plans to use this vehicle for other applications.

[Asteroza]

Is this going to ride exposed on FH like a normal D2 cargo dragon, or be encapsulated in a payload fairing?

I'm also left wondering on the side, this looks a lot like Vast's Haven-1, which is similar in size and will be encapsulated...

[DanClemmensen]

Is this going to ride exposed on FH like a normal D2 cargo dragon, or be encapsulated in a payload fairing?

I'm also left wondering on the side, this looks a lot like Vast's Haven-1, which is similar in size and will be encapsulated...

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.

[cohberg]

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

[StraumliBlight]

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?

[woods170]

Is this going to ride exposed on FH like a normal D2 cargo dragon, or be encapsulated in a payload fairing?

What?

You guys didn't notice the obvious lack of the deployable NDS cover?
And you also managed to miss that there's no mounting points for an external cover over the deployable solar arrays?
Despite the fact that the solar array support posts are represented in this rendering?

Also: the launch is going to be competed. Most of the LSPs eligible to bid on this launch, under NASA-LSP, don't have the hardware (stage-to-payload adapters rated for exposed use) to launch this thing sans fairing.

[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.

[AmigaClone]

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.

Well aware of that.

The initial requote / bolding was responding to Dan regarding the 4 forward nosecone thrusters which are obstructed by the IDA post docking.

Without those 4 thrusters, there are only 12 usable dracos during the deorbit burns (after docking) on cargo dragon (vs the full 16). The context of the debate is the alternate / unlikely paths to free the thrusters up and make the statement reconcile.

Would the Russian segment thrusters and ISS CMG's be used either prior to the initial deorbit burn or between two deorbit burns?

[StraumliBlight]

Would the Russian segment thrusters and ISS CMG's be used either prior to the initial deorbit burn or between two deorbit burns?

At 42:17 in the teleconference, she said the Russian thrusters will continue to be primary for normal attitude control, debris avoidance on the way down, possible altitude lowering depending on fuel remaining and finally as a contingency option if there are multiple failures on the USDV.

[Norm38]

What is driving the requirement to be docked for a year before deorbit?  For what purpose?
And why design the capsule to separate and re-enter for “momentos”?

Wouldn’t those already be packed up?  Or send a dedicated cargo capsule for that.

[Remes]

What is mementos? I haven't seen any plans to depart the usdv. That sounds far too much like fun for NASA.

The crew will leave 6 month before splashdown. So if they dock 1 year earlier, they only have 6 month for scheduling around a limited number of docking ports, do all the check out, tests, etc.

I would assume they will make a few tests with slowing down the station, looking at dynamics, deactivating the existing control system, etc. Those things are not done in a day. Those six month should give them enough time to test and adapt procedures, software, models, ...

A few other thoughts:
- docking earlier: exposes the most vulnerable side of the usdv to the direction of flight. Will there be any removable micro meteorite protection for the trunk?
- docking 1year or later before splashdown: what if something like the launcher has a mishap and the launcher gets grounded? What if the usdv doesn't make it? Will they send up an engineering model or build a second one?

When I heard SpaceX is responsible to deorbit the ISS in 2030 I thought: "nice, ISS will be around till 33/34/...".
And the second thought: "I would have never thought that those words would ever find a place in my brain, but I wish Boeing would have won the contract".

[AmigaClone]

What is driving the requirement to be docked for a year before deorbit?  For what purpose?
And why design the capsule to separate and re-enter for “momentos”?

Wouldn’t those already be packed up?  Or send a dedicated cargo capsule for that.

I suspect most "momentos" will have been returned to Earth by the time the deorbit vehicle has docked. Most would make the return trip in either a Cargo Dragon or Dream chaser but I can see some returning in a crewed vehicle. There might even be an uncrewed Soyuz involved for some Russian "momentos".

[tea monster]

They may want to return the Dragon simply because it's reusable and it's a bit silly to drop it into the ocean.

The irony!

[Jim]

And why design the capsule to separate snip?

Where is that stated?

[Jim]

They may want to return the Dragon simply because it's reusable

it is not after this

[dgmckenzie]

Besides NASA will have bought the Dragon to do with as they want.

[DanClemmensen]

What is driving the requirement to be docked for a year before deorbit?  For what purpose?
And why design the capsule to separate and re-enter for “momentos”?

Wouldn’t those already be packed up?  Or send a dedicated cargo capsule for that.

The USDV is a just an existing Dragon capsule mated to a new-design "trunk". It therefore inherits pretty much all of Dragon's design features, even those it will not use. It will not detach and deorbit separately even though it might have inherited this capability. The deorbit mission requires that it remain attached. It is unlikely that the capsule can separate from the trunk or that is has a heat shield.

There was no mention that the "momentos" would be returned in the USDV. They will be returned in the last crew and cargo vehicles.

[seb21051]

Interesting Stokes-like arrangement of Draco thrusters at the business end of the USDV:

https://spacenews.com/enhanced-dragon-spacecraft-to-deorbit-the-iss-at-the-end-of-its-life/

[Norm38]

And why design the capsule to separate snip?

Where is that stated?

It was a comment upthread, I was replying to that.  The only formal requirement I was questioning was the 1 year loiter time.

[Norm38]

The crew will leave 6 month before splashdown. So if they dock 1 year earlier, they only have 6 month for scheduling around a limited number of docking ports, do all the check out, tests, etc.

So what is the requirement to wait 6 months after the crew departs?  If something goes wrong and the crew isn't there to fix it, deorbit may have to happen sooner.  So why wait?  What is driving that requirement?

[matthewkantar]

The crew will leave 6 month before splashdown. So if they dock 1 year earlier, they only have 6 month for scheduling around a limited number of docking ports, do all the check out, tests, etc.

So what is the requirement to wait 6 months after the crew departs?  If something goes wrong and the crew isn't there to fix it, deorbit may have to happen sooner.  So why wait?  What is driving that requirement?

Just a guess, six months of drag on station will give the delta v available from the deorbit vehicle more authority.

[Jim]

The crew will leave 6 month before splashdown. So if they dock 1 year earlier, they only have 6 month for scheduling around a limited number of docking ports, do all the check out, tests, etc.

So what is the requirement to wait 6 months after the crew departs?  If something goes wrong and the crew isn't there to fix it, deorbit may have to happen sooner.  So why wait?  What is driving that requirement?

it is letting the orbit decay naturally, which reduces propellant required.  There is "nothing" to break on the ISS.   The USDV will be in full control.

[DanClemmensen]

The crew will leave 6 month before splashdown. So if they dock 1 year earlier, they only have 6 month for scheduling around a limited number of docking ports, do all the check out, tests, etc.

So what is the requirement to wait 6 months after the crew departs?  If something goes wrong and the crew isn't there to fix it, deorbit may have to happen sooner.  So why wait?  What is driving that requirement?

it is letting the orbit decay naturally, which reduces propellant required.  There is "nothing" to break on the ISS.   The USDV will be in full control.

Conceivably, there is one thing that might fail and that might be important. If ISS loses pressure, it becomes less  rigid and it also cannot tolerate as much thrust from the USDV. This is a purely theoretical observation since I have no insight into the structural analyses of the ISS as a system. I started thinking about it when I found the reference in the IDSS spec that the IDSS port must be able to handle 100,000 N in tension but only 10,000 N in compression, after Garmund pointed out the tension that comes from the atmospheric presssure. Depressurization will almost certainly affect the harmonic oscillation modes of ISS as it becomes "floppier" if depressurized. The professionals will have already analyzed this and will make the proper adjustments to the control software.

[Jim]

Conceivably, there is one thing that might fail and that might be important. If ISS loses pressure

all the hatches will sealed

[Norm38]

The crew will leave 6 month before splashdown. So if they dock 1 year earlier, they only have 6 month for scheduling around a limited number of docking ports, do all the check out, tests, etc.

So what is the requirement to wait 6 months after the crew departs?  If something goes wrong and the crew isn't there to fix it, deorbit may have to happen sooner.  So why wait?  What is driving that requirement?

it is letting the orbit decay naturally, which reduces propellant required.  There is "nothing" to break on the ISS.   The USDV will be in full control.

Is there a reason they can't simply skip the last Progress reboost?  Or, can Progress also "deboost" the station instead, giving the same drop in altitude?

[Yellowstone10]

Conceivably, there is one thing that might fail and that might be important. If ISS loses pressure

all the hatches will sealed

Once the internal hatches are closed, is there any way to route atmosphere from the NORS tanks in the airlock to other modules?

[DanClemmensen]

Conceivably, there is one thing that might fail and that might be important. If ISS loses pressure

all the hatches will sealed

Once the internal hatches are closed, is there any way to route atmosphere from the NORS tanks in the airlock to other modules?

In the unlikely event that pressurization actually matters, the effect becomes increasingly less important as the modules get farther away from the USDV. That's good because the historically leakiest modules are the farthest away.

[ChrisC]

Looking at an Axiom animation of their assembly sequence today, I realized something that hasn't been discussed anywhere and none of the reporters asked about it in the press conference last week: the Axiom station and this new DV are both planning to use the front docking port.

If the DV is going up 18 months before the deorbit, that implies that all of the Axiom modules need to be launched and assembled and then the entire new Axiom station needs to detach from ISS before that launch.  The first module is currently planned to go up in late 2026, but most of that hardware is planned for "late 2020s". That compresses the Axiom timeline, or at least removes 18 months of wiggle room.  Am I missing something?

(There are some recent videos in the Axiom thread, including an interview with Suffredini 10 days ago, and I'll catch up on those tomorrow and see if this topic comes up.)

[woods170]

Looking at an Axiom animation of their assembly sequence today, I realized something that hasn't been discussed anywhere and none of the reporters asked about it in the press conference last week: the Axiom station and this new DV are both planning to use the front docking port.

If the DV is going up 18 months before the deorbit, that implies that all of the Axiom modules need to be launched and assembled and then the entire new Axiom station needs to detach from ISS before that launch.  The first module is currently planned to go up in late 2026, but most of that hardware is planned for "late 2020s". That compresses the Axiom timeline, or at least removes 18 months of wiggle room.  Am I missing something?

(There are some recent videos in the Axiom thread, including an interview with Suffredini 10 days ago, and I'll catch up on those tomorrow and see if this topic comes up.)

Emphasis mine.

You're not missing anything. Axiom is aware of the constraints. So are NASA and SpaceX. Good thing to keep in mind is this: the PMA and IDA now sitting at the "front" end of ISS, will be relocated to an available CBM on the nadir side of USOS, before the first Axiom module is attached. Both PMA-IDA combinations remain available for docking after Axiom starts its build-up, because crew rotation and cargo delivery requirements require the availability of at least two NDS ports. Docking to the Axiom segments becomes possible only after the second Axiom module is delivered-and-berthed to the first one.

After the Axiom orbital segment is detached, the PMA-IDA has to be moved back to the "front" end of the ISS. As with any relocation of the PMA-IDA combination, that requires the assistance of one-or-more EVAs. Meaning that crew still has to be present on the ISS. Only after the PMA-IDA is back on the "front" end of the ISS, can the USDV perform its final docking to the ISS.

[woods170]

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

The control logics of the Russian segment thrusters and the USOS CMGs are NOT coupled to the control logic of the USDV. This could have the unwanted effect of counter-acting the USDV attitude control system if the RS thrusters and/or the USOS CMGs were to be active during the deorbit burns.

Unlike MIR, the ISS can't enter a slow-spin for stabilisation purposes. Due to the massive truss and its flimsy solar arrays, the rotation velocity of ISS in any direction is much more limited than it was for MIR.

[StraumliBlight]

SpaceX just stomped the competition for a new contract—that’s not great

Here's where all of this leaves NASA. The agency would like to move toward an era of commercial space, in which the agency shares development costs with the private industry and benefits from the ideas and nimble development practices of entrepreneurs. Everyone wins.

However, the space agency has encountered serious turbulence in this endeavor.

Based on the experiences of Commercial Crew and now the US Deorbit Vehicle, on a level playing field, it is clear that traditional space providers such as Boeing and Northrop struggle to compete with SpaceX on price and performance.

But so do newer entrants. For some time, the agency has been hoping that other new space companies would step up and similarly thrive like SpaceX in an environment of purely fixed-price contracts. To succeed over the coming decade in low-Earth orbit and on the Moon, the agency is counting on a new generation of companies, such as Axiom Space and Intuitive Machines, to take this next step. But what happens if they don't?