After seeing this in Security SE

Magnetic core memory isn't quite extinct yet. The two Voyager spacecraft used it and are still functional. Core was/is certainly non-volatile.

I did some interwebbing which led me to Wired.com's 2013 article Interstellar 8-Track: How Voyager's Vintage Tech Keeps Running which contained the NASA image below captioned "Voyager's internal components during assembly."

This well-engineered aluminum structure looks like something that a large group of people could jump up and down on all day without structural issues, though they'd better turn of the attitude control system and the eight track tape player first perhaps.

This made me wonder, after a traumatizing launch with multi gee static and dynamic loads, just what kind of forces a deep space spacecraft actually has to deal with, and is much of the structural mass instantly unwanted dead weight as soon as the spacecraft is launched and off to work on a positive geocentric C3.


  1. How much of a deep space spacecraft's structural mass is useless dead weight after launch and just "along for the ride" and soaking up precious delta-v?
  2. Are there any designs or plans for a spacecraft to shed some of it as soon as it's inserted into an interplanetary trajectory?
  3. Has this already been tried in the past?

Voyager's internal components during assembly - NASA from Wired's "Interstellar 8-Track: How Voyager's Vintage Tech Keeps Running"

  • 2
    $\begingroup$ If it is needed during launch, it is necessary and therefore not a dead weight. Having it along with you cost you no delta-V as, you have already accelerated it. (Well, it still makes correction maneuvers and re-orienteering require more force, but I do not think this is what you meant). To clarify, could you describe what benefits do you expect to be achieved by point 2)? $\endgroup$
    – Suma
    Commented Feb 5, 2021 at 7:41
  • $\begingroup$ Structural items you can jettison safely later are going to be some combination of more massive, more expensive, more complex, and less reliable than structural items that stay put, so there generally needs to be a pretty good reason to bring them along just to jettison them after the spacecraft has already spent most of its delta-V. $\endgroup$
    – notovny
    Commented Feb 5, 2021 at 18:16
  • 1
    $\begingroup$ One note about NH mass: often mentioned 30 kg of scientific payload seems to be the mass of the instruments only (pluto.jhuapl.edu/Mission/Spacecraft.php). It does not include the RTG (with 11 kilograms of plutonium dioxide - planetary.org/space-missions/new-horizons) or communications. $\endgroup$
    – Suma
    Commented Feb 6, 2021 at 8:21
  • 1
    $\begingroup$ Even if a structural element is no longer structurally needed in deep space, it can retain its usefulness in relation to the position of the center of mass, so it is no longer a strictly useless mass. (this beam is there to carry the hole that's been drilled in it in order to balance the whole thing) $\endgroup$
    – user19132
    Commented Feb 6, 2021 at 16:52
  • 1
    $\begingroup$ However, it is pleasant to imagine a payload adapter that's maybe heavier and more complicated, but that would act as a protective exoskeleton during launch, releasing a frail and light probe designed to withstand only the stresses encountered in deep space, and no more. $\endgroup$
    – user19132
    Commented Feb 6, 2021 at 17:45


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