Author Topic: Building a Spacecraft to Deorbit ISS 'Not Optional'.  (Read 5434 times)

Online jstrotha0975

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NASA’s Aerospace Safety Advisory Panel (ASAP) urged the space agency to develop a space tug to deorbit the ISS, saying that the deorbit vehicle is “not optional,”

In this thread we try to figure out a solution.

Source: https://www.msn.com/en-us/news/technology/building-a-spacecraft-to-deorbit-iss-not-optional-claims-nasa-safety-panel/ar-AA1iXJVK

Online jstrotha0975

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #1 on: 10/27/2023 08:06 pm »
I would like to start off. I'm not an aerospace expert but I would like to try. Take an old Dragon 1 capsule and modify it into a space tug. Since it won't be coming back, it doesn't need a heat shield. I think this is the cheapest and easiest solution.

Offline Jim

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #2 on: 10/27/2023 08:11 pm »
I would like to start off. I'm not an aerospace expert but I would like to try. Take an old Dragon 1 capsule and modify it into a space tug. Since it won't be coming back, it doesn't need a heat shield. I think this is the cheapest and easiest solution.

Not big enough and thrusters point the wrong way

Offline Jim

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #3 on: 10/27/2023 08:12 pm »

In this thread we try to figure out a solution.


A larger Cygnus SM is the solution.

Offline Coastal Ron

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #4 on: 10/27/2023 08:21 pm »
I would like to start off. I'm not an aerospace expert but I would like to try. Take an old Dragon 1 capsule and modify it into a space tug. Since it won't be coming back, it doesn't need a heat shield. I think this is the cheapest and easiest solution.

Not big enough and thrusters point the wrong way

Yeah, you'd need to put an engine and propellant tank in the trunk area. Which I'm sure could be done if you extended the length of the trunk, but not sure if this is the right approach.


In this thread we try to figure out a solution.


A larger Cygnus SM is the solution.

I like Cygnus as a tug concept in its current size, so this solution seems to make sense - NASA pays for the up-sized service module, and Northrop Grumman gets a new product to offer to the market - Win-Win!  :D
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Online jstrotha0975

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #5 on: 10/27/2023 08:26 pm »
I forgot to mention in my previous posts that the solution needs to be as cheap as possible due to possible budget cuts according to the source article I posted.
« Last Edit: 10/27/2023 08:26 pm by jstrotha0975 »

Online DanClemmensen

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #6 on: 10/27/2023 08:29 pm »
A larger Cygnus SM is the solution.
To minimize development time and expense, is it possible to use multiple Cygnuses (Cygni?)  serially?

Online Yellowstone10

I would like to start off. I'm not an aerospace expert but I would like to try. Take an old Dragon 1 capsule and modify it into a space tug. Since it won't be coming back, it doesn't need a heat shield. I think this is the cheapest and easiest solution.

Not big enough and thrusters point the wrong way

I'm curious what the back-of-the-envelope numbers suggest would happen if you attached a Crew Dragon to IDA-2 and then burned the SuperDracos to depletion. Probably not enough propellant, but how much are we off by?

Offline Sam Ho

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #8 on: 10/27/2023 09:19 pm »
I would like to start off. I'm not an aerospace expert but I would like to try. Take an old Dragon 1 capsule and modify it into a space tug. Since it won't be coming back, it doesn't need a heat shield. I think this is the cheapest and easiest solution.

Not big enough and thrusters point the wrong way

I'm curious what the back-of-the-envelope numbers suggest would happen if you attached a Crew Dragon to IDA-2 and then burned the SuperDracos to depletion. Probably not enough propellant, but how much are we off by?

SuperDraco has far too much thrust.  There is an existing thread discussing the Deorbit RFI.  The Deorbit Module needs to provide 3-6kN of thrust (maybe higher if it can ramp up slowly).

twitter.com/jeff_foust/status/1560739973833412608

Quote
NASA issued an RFI today looking for industry input on a proposed deorbit module for the ISS to bring it down at the end of its life, something originally projected to be done by Progress cargo spacecraft. https://sam.gov/opp/74252cfe7d49416abae0977fe4fd503c/view

https://twitter.com/jeff_foust/status/1560740299680497667

Quote
From a NASA statement: ISS partners “developed a strategy and action plan that evaluated the use of multiple Roscosmos Progress spacecraft to support deorbit operations. These studies indicated additional spacecraft may provide more robust capabilities for deorbit.”

Online AmigaClone

A larger Cygnus SM is the solution.
To minimize development time and expense, is it possible to use multiple Cygnuses (Cygni?)  serially?

I agree that using the Cygnus SM as the basis for the design of the deorbit module might be the cheapest solution. In theory, it wouldn't need a full-sized cargo module, although keeping it might reduce the complexity of the project.

Quote
I'm curious what the back-of-the-envelope numbers suggest would happen if you attached a Crew Dragon to IDA-2 and then burned the SuperDracos to depletion. Probably not enough propellant, but how much are we off by?

One thing to remember is that according to current plans, the forward CBM of the Harmony module will be empty with the PMA-2/IDA-2 having been relocated when the first Axiom module arrives.

Online DanClemmensen

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #10 on: 10/27/2023 09:46 pm »
A larger Cygnus SM is the solution.
To minimize development time and expense, is it possible to use multiple Cygnuses (Cygni?)  serially?
I agree that using the Cygnus SM as the basis for the design of the deorbit module might be the cheapest solution. In theory, it wouldn't need a full-sized cargo module, although keeping it might reduce the complexity of the project.
Even the most trivial modification would require a development project, and any depelopment project costs time and money. I was asking about just using multiple Cygnus units of the existing design. Zero development time. Zero development cost. After the last crew performs the berthing of the last Cygnus in this sequence, they turn off the lights and go home on their CCP spacecraft, and then that last Cygnus is fired up for the final deorbit burn.

Offline AS_501

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #11 on: 10/27/2023 09:55 pm »
I assume the two large engines on the rear of Zvezda are not up to the task or long out of commission(?).
Launches attended:  Apollo 11, ASTP (@KSC, not Baikonur!), STS-41G, STS-125, EFT-1, Starlink G4-24, Artemis 1
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Online Yellowstone10

SuperDraco has far too much thrust.  There is an existing thread discussing the Deorbit RFI.  The Deorbit Module needs to provide 3-6kN of thrust (maybe higher if it can ramp up slowly).

Sure, but just in terms of the total amount of propellant needed to do the job, assuming a typical NTO/MMH thruster, how does that compare to "one Dragon's worth of fuel" as a reference point?

Offline Sam Ho

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #13 on: 10/27/2023 10:40 pm »
SuperDraco has far too much thrust.  There is an existing thread discussing the Deorbit RFI.  The Deorbit Module needs to provide 3-6kN of thrust (maybe higher if it can ramp up slowly).

Sure, but just in terms of the total amount of propellant needed to do the job, assuming a typical NTO/MMH thruster, how does that compare to "one Dragon's worth of fuel" as a reference point?
Also from that same presentation, the delta-V requirement is 41-47m/s, plus 700-1700kg of attitude control propellant.  So, about 3 Dragons' worth of fuel.

Offline Jim

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #14 on: 10/28/2023 12:13 pm »
I forgot to mention in my previous posts that the solution needs to be as cheap as possible due to possible budget cuts according to the source article I posted.

No, this is going to cost what it is going to cost.

Offline Jim

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #15 on: 10/28/2023 12:14 pm »
A larger Cygnus SM is the solution.
To minimize development time and expense, is it possible to use multiple Cygnuses (Cygni?)  serially?
I agree that using the Cygnus SM as the basis for the design of the deorbit module might be the cheapest solution. In theory, it wouldn't need a full-sized cargo module, although keeping it might reduce the complexity of the project.
Even the most trivial modification would require a development project, and any depelopment project costs time and money. I was asking about just using multiple Cygnus units of the existing design. Zero development time. Zero development cost. After the last crew performs the berthing of the last Cygnus in this sequence, they turn off the lights and go home on their CCP spacecraft, and then that last Cygnus is fired up for the final deorbit burn.

Needs to be a single vehicle

Offline Jim

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #16 on: 10/28/2023 12:15 pm »
It is going to need about 15 tons of biprop.

Offline Emmettvonbrown

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #17 on: 10/28/2023 04:22 pm »
Desorbiting 400 metric tons is no picnic, even if it only takes 50 m/s or 100 m/s of braking... that's 400 mt.

I remember that Mir was desorbited by a Progress, but it was 1/4 the weight.

Online DanClemmensen

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #18 on: 10/28/2023 04:47 pm »
A larger Cygnus SM is the solution.
To minimize development time and expense, is it possible to use multiple Cygnuses (Cygni?)  serially?
I agree that using the Cygnus SM as the basis for the design of the deorbit module might be the cheapest solution. In theory, it wouldn't need a full-sized cargo module, although keeping it might reduce the complexity of the project.
Even the most trivial modification would require a development project, and any depelopment project costs time and money. I was asking about just using multiple Cygnus units of the existing design. Zero development time. Zero development cost. After the last crew performs the berthing of the last Cygnus in this sequence, they turn off the lights and go home on their CCP spacecraft, and then that last Cygnus is fired up for the final deorbit burn.

Needs to be a single vehicle
I believe you, but I am too ignorant to know why this is true, so I would appreciate it if you would educate me. If the earlier small burns get it low enough, maybe that last Cygnus would not have enough energy to cause a precise enough de-orbit?

Online Perchlorate

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #19 on: 10/28/2023 05:16 pm »

In this thread we try to figure out a solution.


A larger Cygnus SM is the solution.

Inconceivable that one would use anything but a Cygnus for the ISS' "swan song."
Pete B, a Civil Engineer, in an age of incivility.

Offline Stan-1967

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #20 on: 10/28/2023 05:31 pm »
It is going to need about 15 tons of biprop.

So the existing Cygnus PCM looks to have enough internal volume for 15 tons of prop.  Would a modified Cygnus focus on converting the internal volume to tankage that feeds the service module?  Alternately do you shrink the Cygnus PCM, keeping just the docking interface, and integrate larger tanks into the service module? 

ISTM that pressure fed hypergolics probably would favor not doing a "crossfeed" from tanks in the PCM, and rather would prefer expanding the tanks of the SM.  It may also be that the SM control system is not designed for controlling a near 18t fully loaded vehicle.  No easy modifications look possible.

Also looks like Vulcan, FH, and maybe F9 ( expendable) could get it to the ISS within a standard fairing.
« Last Edit: 10/28/2023 05:37 pm by Stan-1967 »

Offline bobthemonkey

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #21 on: 10/28/2023 07:51 pm »
The Cygnus SM is derived from reasonably standardised components from various LEO and Satellite buses, and there was some design work (unsure whether it went further than conceptual) for an unpressurised cargo carrier variant of Cygnus. This was essentially a strongback/spine for unpressurised payloads with a CBM up front.

It wouldn't be too far of a stretch (keeping in mind Jims 'Rockets aren't Lego' maxim) to see a similar design reappear, but with multiple existing bi-prop tanks instead of ORUs linked to some kind of manifold feeding into the existing SM fuel system - possibly with additional engines for redundancy.

Online Yellowstone10

Are you proposing equipping Cygnus with an alternate engine?

What existing engines are there in that 3 to 6 kN thrust range, I wonder? (With the exception of the KTDU-80 on the Soyuz, because I suspect that's politically infeasible.)

Online Yellowstone10

I believe you, but I am too ignorant to know why this is true, so I would appreciate it if you would educate me. If the earlier small burns get it low enough, maybe that last Cygnus would not have enough energy to cause a precise enough de-orbit?

I think that's exactly the case. You need one spacecraft with enough delta-V to drop the ISS from "low-but-stable orbit" to "will do exactly one-half more orbit before it's in the drink" in one burn. If you stop halfway through, then who knows how many more perigees it can survive before re-entry? And each of those perigees is 2,200 km west of the previous one.

Offline Zed_Noir

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #24 on: 10/28/2023 11:14 pm »
<snip>
To this point, the deorbit vehicle requires at least 3.2kN (up to 6.2 kN desired) of thrust for the final deorbit burn / entry shaping.
Cygnus is currently equipped with one BT-4 (developing 0.5kN of thrust) which is significantly below the thrust requirements.

Quote from: ISS Deorbit USOS Concept of Operations Overview - Design Considerations
The deorbit vehicle will need to provide at least 3236 N thrust to hit the target delta v (30 m/s) within a 60 minute time period.

Is the proposal to create a 7 - 13 engined Cygnus?
Are you proposing equipping Cygnus with an alternate engine?
Estimate modifying the Cygnus with additional engines and extra tankage versus building a new spacecraft is about the same cost.

Online DanClemmensen

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #25 on: 10/30/2023 09:02 pm »

One thing to remember is that according to current plans, the forward CBM of the Harmony module will be empty with the PMA-2/IDA-2 having been relocated when the first Axiom module arrives.
Yuck. I was thinking(?) fantasizing that the only spacecraft currently being developed that can Deorbit ISS, without any hardware modifications, is Starship HLS. But if it cannot dock its nose IDSS port to Harmony forward, then hardware development would be needed to dock it to some appropriate place on ISS, and a custom solution might be cheaper after all.

If PMA-2+IDA-2 were still in place, an instance of Starship HLS would probably work nicely, and the deorbit mission could probably be designed so HLS could undock and save itself instead of going down with ISS. It would then be available in the correct plane to become a module of the Axiom station.
« Last Edit: 10/30/2023 09:03 pm by DanClemmensen »

Offline Zed_Noir

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #26 on: 10/30/2023 10:19 pm »

One thing to remember is that according to current plans, the forward CBM of the Harmony module will be empty with the PMA-2/IDA-2 having been relocated when the first Axiom module arrives.
Yuck. I was thinking(?) fantasizing that the only spacecraft currently being developed that can Deorbit ISS, without any hardware modifications, is Starship HLS. But if it cannot dock its nose IDSS port to Harmony forward, then hardware development would be needed to dock it to some appropriate place on ISS, and a custom solution might be cheaper after all.
<snip>
Could bring up a self propelled adapter module that got the IDSS docking ring on end and the Russian SSVP docking system on the other end in the HLS cargo hold. Then push with the HLS with the adapter module from the Russian side of the ISS. Of course getting a SSVP docking system might be problematic. Maybe Roscosmos is open to some sort of bartering.

Offline Jim

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #27 on: 10/31/2023 12:49 am »

Yuck. I was thinking(?) fantasizing that the only spacecraft currently being developed that can Deorbit ISS, without any hardware modifications, is Starship HLS. But if it cannot dock its nose IDSS port to Harmony forward, then hardware development would be needed to dock it to some appropriate place on ISS, and a custom solution might be cheaper after all.

If PMA-2+IDA-2 were still in place, an instance of Starship HLS would probably work nicely, and the deorbit mission could probably be designed so HLS could undock and save itself instead of going down with ISS. It would then be available in the correct plane to become a module of the Axiom station.

that would be wrong.  too high of thrust. And it can not undock.   Entry is too close to deorbit.

Online DanClemmensen

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Re: Building a Spacecraft to Deorbit ISS 'Not Optional'.
« Reply #28 on: 10/31/2023 01:23 am »

Yuck. I was thinking(?) fantasizing that the only spacecraft currently being developed that can Deorbit ISS, without any hardware modifications, is Starship HLS. But if it cannot dock its nose IDSS port to Harmony forward, then hardware development would be needed to dock it to some appropriate place on ISS, and a custom solution might be cheaper after all.

If PMA-2+IDA-2 were still in place, an instance of Starship HLS would probably work nicely, and the deorbit mission could probably be designed so HLS could undock and save itself instead of going down with ISS. It would then be available in the correct plane to become a module of the Axiom station.
that would be wrong.  too high of thrust. And it can not undock.   Entry is too close to deorbit.
I was assuming an HLS with mid-mounted hot gas lunar landing thrusters. If it cannot save itself, then it's expended, and you would of course use a minimal configuration, not a fully-configured HLS. However, even though Starships are relatively cheap, the cost is high enough that it may exceed the cost designing and manufacturing a special-purpose deorbiter. It's a non-starter anyway if the Harmony forward IDSS dock is absent.

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