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> Why wasn't 5 Hubble telescopes launched? The marginal cost for the other 4 must have been vastly smaller than the first. Economies of scale only apply at, we

> Why wasn't 5 Hubble telescopes launched? The marginal cost for the other 4 must have been vastly smaller than the first. Economies of scale only apply at, well, scale. Five Hubbles would cost 5x one Hubble to construct. There's very little in the way of savings because most parts are custom fabricated. The parts need to be tested, integrated, then tested after integration. The testing and verification of each subsystem takes the same number of person-hours. So testing 5x the systems requires 5x the time. You can't just accept a high failure rate of something the size of Hubble just because you've built five of them. If you launched a Hubble and it failed in some Loss of Vehicle fashion after inserted into orbit you've got a big uncontrollable mass of telescope flying around the Earth. Even if we still had the Space Shuttle (or a fantasy version of the SpaceX Starship) flying an uncontrollable Hubble couldn't necessarily be retrieved. If it wasn't accepting commands and was spinning on some axis it would be too dangerous to approach with another vehicle. Even an unmanned vehicle couldn't necessarily approach it without a collision that causes even more problems. See the recent idiotic Russian ASAT test for an object lesson in what could happen. This is all to say you don't want some large satellite in a long lived orbit to fail. So there's no savings on testing and verification. Even though at launch Hubble's mirror had problems the satellite itself was fully under control and operable. Something like Starlink is very different. All the satellites in a given block are functionally identical and fungible. If one fails it's easily replaced by another. They also deploy to a low unstable orbit. If a Starlink satellite fails and is uncontrollable it will de orbit by itself quickly. They must be functional to enable the onboard engines that get them to a stable intended orbit. A Starlink satellite then needs far less testing and verification than a Hubble or JWST, not that they can be poor quality but they don't need to function Or Else Bad Things.

mbfg 5y ago
Is that really true? I'm guessing a big part of the cost is figuring out how to actually invent stuff needed for the project. That knowledge is now known. That cost is now 0.
- bumby 5y ago
  >There's very little in the way of savings because most parts are custom fabricated. The parts need to be tested, integrated, then tested after integration. To piggy back on the the GP's point, the fabrication research is only one small cost center. Quality control costs much more in aerospace than many people realize. The reason why a bolt may cost $150 is because it has to be tracked, material coupons kept/tracked/tested, held in bonded storage etc. and not because we had to figure out how to make a bolt. Those costs don't come down as much with scale as, say, raw material. If it were all about knowledge costs, many designs today would be dramatically cheaper because many use technology (and even refurbished rockets) from 50 years ago.
- Quenty 5y ago
  Just because the knowledge exists in the world doesn’t mean that you know it. Consolidating knowledge is a non-trivial exercise.
- giantrobot 5y ago
  > I'm guessing a big part of the cost is figuring out how to actually invent stuff needed for the project. We're talking about marginal costs, not development costs. So the cost to invent a component is already out of the equation. The high production cost of something like Hubble comes from testing and validation more than materials or fabrication. The failure modes for something big in space can be extremely dangerous. Even a tiny "cheap" cubesat requires a lot of relatively expensive testing so there's a reasonable assurance it won't fail in some catastrophic fashion and destroy the entire rocket. Testing space hardware is additionally difficult because you can only just approximate the hardware's operating environment on the ground. Space hardware also can't be easily repaired or repaired at all once launched. So you've got to test actual flight hardware and if it fails possibly rebuild it from scratch testing and validating the entire way. Developing space hardware and high precision science instruments is expensive and difficult. But it's just a small portion of the overall mission cost for something like Hubble or JWST.
  - mbfg 5y ago
    I defer to your knowledge, i'm not trying to be a jerk. But Hubble took like 30 years? or so to develop and build? How long would a second Hubble take? I'd have to imagine it's less than 5 years, no? That has to be a huge cost savings. The testing process would have to be more streamlined or efficient, i would think. You have a much better understanding of failure modes.
deleted 5y ago
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jinto36 5y ago
If they had built five Hubbles that each had defective mirrors and all of them needed a shuttle visit to correct the issues and make them usable...
XorNot 5y ago
The US absolutely could've built 5 Hubbles - because it did, they just don't look at Space - they look at Earth. The Hubble is basically a KH-11 spy sat chassis. NASA was given a gentle suggestion that if the optics package was a particular size, there was definitely a company in the US which could polish lens and mirror packages of exactly that size. [1] https://en.wikipedia.org/wiki/KH-11_KENNEN https://en.wikipedia.org/wiki/KH-11_KENNEN

mbfg 5y ago

Is that really true? I'm guessing a big part of the cost is figuring out how to actually invent stuff needed for the project. That knowledge is now known. That cost is now 0.

bumby 5y ago
>There's very little in the way of savings because most parts are custom fabricated. The parts need to be tested, integrated, then tested after integration. To piggy back on the the GP's point, the fabrication research is only one small cost center. Quality control costs much more in aerospace than many people realize. The reason why a bolt may cost $150 is because it has to be tracked, material coupons kept/tracked/tested, held in bonded storage etc. and not because we had to figure out how to make a bolt. Those costs don't come down as much with scale as, say, raw material. If it were all about knowledge costs, many designs today would be dramatically cheaper because many use technology (and even refurbished rockets) from 50 years ago.
Quenty 5y ago
Just because the knowledge exists in the world doesn’t mean that you know it. Consolidating knowledge is a non-trivial exercise.
giantrobot 5y ago
> I'm guessing a big part of the cost is figuring out how to actually invent stuff needed for the project. We're talking about marginal costs, not development costs. So the cost to invent a component is already out of the equation. The high production cost of something like Hubble comes from testing and validation more than materials or fabrication. The failure modes for something big in space can be extremely dangerous. Even a tiny "cheap" cubesat requires a lot of relatively expensive testing so there's a reasonable assurance it won't fail in some catastrophic fashion and destroy the entire rocket. Testing space hardware is additionally difficult because you can only just approximate the hardware's operating environment on the ground. Space hardware also can't be easily repaired or repaired at all once launched. So you've got to test actual flight hardware and if it fails possibly rebuild it from scratch testing and validating the entire way. Developing space hardware and high precision science instruments is expensive and difficult. But it's just a small portion of the overall mission cost for something like Hubble or JWST.
- mbfg 5y ago
  I defer to your knowledge, i'm not trying to be a jerk. But Hubble took like 30 years? or so to develop and build? How long would a second Hubble take? I'd have to imagine it's less than 5 years, no? That has to be a huge cost savings. The testing process would have to be more streamlined or efficient, i would think. You have a much better understanding of failure modes.

deleted 5y ago

[deleted]

jinto36 5y ago

If they had built five Hubbles that each had defective mirrors and all of them needed a shuttle visit to correct the issues and make them usable...

XorNot 5y ago

The US absolutely could've built 5 Hubbles - because it did, they just don't look at Space - they look at Earth. The Hubble is basically a KH-11 spy sat chassis. NASA was given a gentle suggestion that if the optics package was a particular size, there was definitely a company in the US which could polish lens and mirror packages of exactly that size. [1] https://en.wikipedia.org/wiki/KH-11_KENNEN https://en.wikipedia.org/wiki/KH-11_KENNEN