# Why space probes are so different from each other?

Everytime I look at a space probe I see a whole different design and this puzzles me.

I do understand that each mission is different and requires different science instruments. I also do understand that for each launch, the amount of available mass is different and thus probe designers might need to use radical designs each time.

However, I struggle to understand why there isn't a common design or a standardized structure that space agencies can reuse trying to save costs?

Is it because in such a mission-specific project the costs savings related to using a similar layout are almost none, since most of the efforts are focused on designing specific science instruments rather than the probe chassis?

I am also thinking about the nanosat example, where most of the components (as well as the chassis) are made with standard pieces.

• I think it is because astrophysicists have to push the limit in order to get new data. The marginal results of a second copy of the Hubble telescope would not be at all as revolutionary as HST itself was. For astronomy purposes anyway, the probes will always be as expensive as anyone wants to pay for. That's the limit, and astronomers are always there. Otherwise it wouldn't be very interesting. It'd only be gentlemens 19th century Paris balcony astronomy leasure. – LocalFluff Aug 12 '15 at 12:50
• I think you answered your own question in your question. Standard pieces won't be designed until the probes are produced en mass. – punkerplunk Aug 12 '15 at 13:39
• If you read about Ranger, Mariner, Pioneer (10 & 11), and Voyager, there is a sort of design evolution with a certain continuity (re-use), in spite of widely varying mission requirements. – Anthony X May 24 '16 at 3:28
• – Hobbes May 24 '16 at 14:44

## 2 Answers

Rather than establishing a common design for space probe construction, the aerospace industry establishes common standards for managing construction. This makes more sense with the scope and life cycle of these types of projects.

When probes are rare and have very specific destinations and purposes--and need to be constructed in a cost-managed, timely fashion--you don't want to constrain the design where you don't have to. You want to give the designers the freedom to maximize success for the probe, because often these are one-shot missions--if you fail, you may not get funding for a retry.

That isn't to say that there aren't situations in which it is appropriate to reuse designs. For example, the Mars 2020 rover is planned to use a similar design to the Curiosity rover with different science instruments. Curiosity's design has proven to be effective in navigating the Martian terrain, so it makes sense to reuse parts of the design for another rover. Notice that NASA sent four rovers to more or less the same terrain before they decided to reuse the design. There were a lot of lessons to learn before reusing design made sense.

• Mars Phoenix is another good example - it was the third mission with that basic chassis, after the failed Polar Lander and the cancelled Surveyor. – Andrew Aug 12 '15 at 17:23

In addition to the main reasons in other answers, it's important to note that the cost savings from standard frames, modular parts, and mass production is that each additional unit spreads the research, design, and startup costs around. This is a huge savings when you are going to make 1million cars each year for the next 5; but when you are only making 2 or 3 units ever year or three, and then launching them on a very expensive rocket, there just isn't that much benefit.

• That's a good reason for why space probes aren't necessarily made similar, but it's not necessarily an equally good reason for why to make them different. If one approach costs \$1000 million, and another costs \$990 million, and the two gets similar results, the \$10 million savings means you can pack another \$10 million of science within the same budget. – a CVn May 24 '16 at 14:11
• Yes, that's correct. I posted an answer because it's a minor point but too long for a comment, the other answer is more pertinent. – nexus_2006 May 24 '16 at 20:22
• that reuse would get similar results is a very large assumption for designs that are consistently pushing the limits of engineering. – Leliel May 25 '16 at 6:23
• @Leliel that is addressed in called2voyage's answer. Sometimes reusing a design is a better choice, but not typically. – nexus_2006 May 25 '16 at 11:26