Cruise missile engines are relatively smaller in size. However, they might need the same level of expertise e.g. metallurgy, single-crystal blades, etc.
Do the design and manufacturing of cruise missile engines and aircraft jet engines require the same level of effort in terms of experience, infrastructure, and R&D investment?
Please, explain: Why.
The service life of a cruise missile engine is a few hours at most, while airplane engines lasts 1000 hours at least. This alone makes things orders of magnitudes easier.
Also the engine accounts for less than 5% of the weight of a missile but more than 15% on a jet fighter, so less effort could be spent on weight reduction.
Additionally, for surface-launched cruise missiles, the weight budget of the missile is almost unlimited, meaning it could carry arbitrarily large amount fuel to compensate for bad fuel economy. The limiting factor for the range of the missile is more often navigation and homing, rather than fuel and fuel economy.
Finally, a cruise missile flies a at very predictable altitude and air speed and doesn't maneuver much, and always runs at full thrust. As a result, problems like compressor chocking and vibration only needs to be solved for those relatively simple working conditions.
As a matter of fact, other than some long range air-launched cruise missiles that are more constrained by weight and size (e.g. AGM-86), most cruise missiles below 300 km range are quite OK with turbojets even today.
As mentioned in the comments here, those comparisons are only between a cruise missile and military airplane. If you add civilian/commercial (passenger) airplanes to the scene, you'll have to deal with even more complications, such as:
The list goes on and on. In short, an cruise missile engine is a minimum use case, i.e to generate sufficient thrust with acceptable amount of fuel for relatively short period of time, but airplanes engines, especially commercial ones, are concerned with much beyond that.
An important difference between cruise missile engines and aircraft engines is their lifecycle.
A cruise missile has to perform only a single start and a single flight of at most a few hours. It is then disposed in an almighty bang. The majority of lifecycle costs are in the engineering and production (labour + materials).
A jet engine has to perform many starts, many flight hours. It goes through many temperature cycles. It will be maintained to extend its life. The total cost of the fuel it burns is a significant part of the lifecycle cost, and so are the maintenance costs. For jet engines, additional engineering costs to improve the fuel efficiency or reduce maintenance costs give a better return on investment than for missile engines.
Based on that,I expect the jet engine to require a higher level of effort in terms of experience, infrastructure, and R&D investment.
Not even the same order of magnitude.
The development costs for engines rank as follows:
Transport aviation >= Military jets >> Missiles
Some details on military engines are available in a report (admittedly an old one). It shows 100M to 1B to be spent on development per engine model. Smaller engines do cost less to develop. For major civil engines, the cost is up to 2B.
Most military engines are relatively low-tech, compared to airliners. Their reliability, efficiency and certification requirements are very relaxed. Fewer advanced technologies are used, simpler blade cooling, sometimes lower turbine inlet temperatures. A military engine will generally require more maintenance and repairs per flight hour compared to a civil engine of the same era.
However, special performance requirements, often unrealistic initial expectations, and large government budgets lead to some major high-cost military developments as well. Every once in a while, some of them do bear fruit.
For cruise missiles, the engine is almost an off-the-shelf item. The simple reason is that the greatest cost drivers in an aerial engine are reliability and fuel efficiency.
As far as reliability, missile engines are disposable items with low performance requirements. A reliability level of less than 99% per flight is considered sufficient for them. Some cruise missiles are expected to fail to launch or fail underway. More will fail for other reasons.
While efficiency means range for the military, turbofans already offer such an overwhelming advantage over rockets and ramjets that there's no need to work on a better turbofan to extend their range any further.
Simplicity is even more important in missiles, since their engines have to spend years in storage before actually being used.
