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Cygnus is the second of the most commonly known ISS resupply freighters (the only more commonly used one is progress.) After cygnus launches aboard it's Antares rocket, it rendezvouses with the ISS, and is attached to the station, allowing for vital supplies to be unloaded from the noble ship and used by crewmembers. There's one flaw, one money wasting flaw, once cygnus undocks from the ISS however long later, it is sent back to earth (likely full of garbage) to burn up in the atmosphere. I've been running simulations on my phone, and I've found a few ways you can safely return a cargo ship to the earth. Currently, I only know of 2 reusable cargo ships for the ISS, the dragon 1, and the dreamchaser (in development). My question is, could you modify cygnus to be reusable? Edited: you don't have to recover the service module, just the part of the spacecraft that is actually used on the ISS (the cargo portion). This edit should make this question easier to answer.

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    $\begingroup$ Is it really money wasting? How much more expensive would making it reusable cost? $\endgroup$
    – Topcode
    Oct 25, 2022 at 20:03
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    $\begingroup$ Cygnus doesn't actually dock, it's grappled with the arm and berthed to the station. Not sure I've heard "Dragon 1" used before, but if you're trying to differentiate between the berthing dragons and the docking dragons (which were commonly known as Dragon 2 for a while), both were reusable. $\endgroup$
    – Erin Anne
    Oct 25, 2022 at 21:04
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    $\begingroup$ @ColonelCornieliusCornwall it's really not anymore, because there are crew and cargo versions of the docking Dragon. The lack of clarity in the naming was a thorn in my paw for years as the berthing Dragon missions wrapped up but I was working exclusively on docking Dragon, which we started calling Crew Dragon or Dragon 2 as well, but then the new Cargo Dragon came along too. :/ $\endgroup$
    – Erin Anne
    Oct 25, 2022 at 22:41
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    $\begingroup$ @ColonelCornieliusCornwall eh, it’s more like if we threw out the box when we got a package, which we do. $\endgroup$
    – Topcode
    Oct 25, 2022 at 23:02
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    $\begingroup$ Please, please, expand on this fascinating topic - "I've been running simulations on my phone, and I've found a few ways you can safely return a cargo ship to the earth." $\endgroup$ Oct 25, 2022 at 23:33

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The original proposal for Cygnus included three variants, all utilizing a common Service Module. Attached to the Service Module would be one of three different cargo modules

  1. Pressurized Cargo Module (PCM), aka Cygnus as we know it today.

enter image description here

  1. Unpressurized Cargo Module (UCM), for the sort of stuff cargo Dragons carry in the trunk

enter image description here

  1. Return Cargo Module (RCM), an entry capsule to, um, return cargo to Earth. This variant would have discarded the Service Module and recovered the capsule portion.

enter image description here

References to the RCM vanished very early on, and the UCM not long thereafter.

I do not remember if the RCM was intended to be reusable, but it would not be out of the realm of possibility. Even if the RCM had been reusable, the Service Module would still have been expended on every mission.

References (All sub-pages of Gunter's Space Page)

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    $\begingroup$ argh I completely forgot about the other cargo module variants. Glad they never came to pass, honestly, since Cygnus really shines with its huge pressurized space $\endgroup$
    – Erin Anne
    Oct 26, 2022 at 0:40
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    $\begingroup$ @ErinAnne since they basically had the PCM designed already (from the MPLM) the other 2 would have taken a lot more up front money, so it's easy to see why they vanished. $\endgroup$ Oct 26, 2022 at 0:43
  • $\begingroup$ @OrganicMarble to answer you about my simulations, basically, I used an app called "spaceflight simulator" to make a Cygnus replica in 4 major configurations, 1. a separate capsule returns to the earth for reuse. 2. cover the whole thing in heat shields and parachutes. 3. regular cygnus but it deploys the inside of the cargo bay as a separate capsule. 4. a separate spacecraft collects the garbage the Cygnus was filled with on departure, then Cygnus folds up and deploys 2 inflatable heat shields, forming a capsule. One of the shields is then jettisoned and a parachute deploys, (continued) $\endgroup$ Oct 26, 2022 at 16:13
  • $\begingroup$ @OrganicMarble Cygnus then uses an engine to slow down completely. $\endgroup$ Oct 26, 2022 at 16:14
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    $\begingroup$ @ColonelCornieliusCornwall I really really hope you don’t think that SFS is an accurate simulator $\endgroup$
    – Topcode
    Oct 27, 2022 at 22:27
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(for the purposes of this answer, "Cygnus" refers to the version of the vehicle that was ultimately produced, using the pressurized cargo module, and not the other variants that used the same service module.)

This can really only be start to be answered properly with an engineering study. I can't find one for Cygnus, or recall any prior attempts to make an expendable orbital spacecraft into a reusable one, except for Falcon 9 Stage 2; not finding any great authoritative resources on what the plan was or how far it got before the pivot to Starship, but Space SE discusses F9 S2 recovery here and here and perhaps elsewhere.

PearsonArtPhoto has ninja'd most of the concerns I have, both philosophical (is it really a Cygnus anymore?) and practical:

  • Cygnus flies to orbit inside an aerodynamic fairing (see e.g. this tweet from the NASA Landsat account, chosen because it's a relatively recent Cygnus mission) and would need to retain a (subtly different) aerodynamic shape for entry. This outer shell would also need to protect it from re-entry heating.

  • It's not immediately clear how it would land. To still be a Cygnus, you'd want to retain the main engine, which has been used to reboost the space station. The sides of the pressurized cargo module probably aren't good candidates for landing on; likely you'd want to land on the service module to keep the CG low. That probably means landing legs to clear the main engine bell (or attempting the scheme discussed for F9 S2 above and trying to retract the engine inside a heat shield you could splash down on). It also probably means parachutes, and finding places to put those...and good god, the engineering that goes into parachutes is completely ridiculously exceptionally difficult. As an example, the tests for CPAS (the Orion spacecraft parachutes) went on for 10 years. I know some of the people who supported that and it was exhausting work.

  • Cargo downmass may or may not be an option; since re-entry G loads are typically higher than launch G loads, if you want to put that reusability to work.

  • The Cygnus solar arrays aren't designed to be retracted, so either that capability would need to be added or the arrays would need to be releasable for entry.

Every bit of that eats into your payload upmass, which is apparently already lower than Cargo Dragon's, though Cygnus has much more pressurized cargo volume, a bigger door (CBM versus the docking adapter), and I think some more specialized payload capability to power payloads, though I'm having trouble finding a Cargo Dragon Payload User's Guide to compare to this admittedly dated Cygnus document with reasonable details about its cargo capability.

You would also likely miss out on experiments like the largest man-made fire in space and be less likely to fill the spacecraft with trash if it were expected to be landed and re-used, though I know Alice Gorman would probably adore the chance to go through discarded items from ISS and other engineers would probably leap at the chance to analyze the aftermath of a major fire in a(n otherwise empty) spacecraft if it still managed to land.

My own personal thoughts: not worth it for a spacecraft with this kind of launch tempo which launches on expendable launchers anyway. Reusability is great and kudos to SpaceX for turning public perception of it around; during my aerospace engineering education, plenty of smoke was blown about how the Shuttle program had demonstrated that reusing spacecraft was expensive and time-consuming folly. There's every reason to continue pursuing reusability, but retrofitting it doesn't make sense unless the near-future reusable spacecraft we're aware of, like Starship, don't come to be.

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  • $\begingroup$ Check out that picture of the MCC on the last page of the "dated Cygnus document". $\endgroup$ Oct 27, 2022 at 1:17
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    $\begingroup$ @OrganicMarble not only did they not know where Houston is, they don't know what's in it $\endgroup$
    – Erin Anne
    Oct 27, 2022 at 3:32
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You could theoretically, but it'd be a lot of work, basically a new spacecraft. It'd need a heat shield, other heat protection, and the ability to fly aerodynamically. By the time all of this is taken in to account, it's a new spacecraft with a bit of resemblance to the existing one.

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  • $\begingroup$ If you look at my comment, on Organic Marble's answer, you'd see that one simulation that worked was to cover it with heat shields and parachutes. $\endgroup$ Oct 26, 2022 at 16:18

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