*The following essay was contributed by space systems engineer Kostas Konstantinidis*

A spacecraft launcher is a rocket-propelled vehicle used to carry a payload from Earth's surface to space, usually to Earth orbit or beyond. Typical spacecraft launchers are expendable, with rocket stages either [falling back onto Earth](https://mars.nasa.gov/mer/mission/timeline/launch/launch-diagram/), or remaining in orbit as space debris. Being able to recover and reuse parts or the whole of a launcher can thus have a significant impact on lowering launch costs. And indeed, launch cost reduction was part of the rationale behind the first reusable launcher system, the [Space Shuttle](https://www.nasa.gov/mission_pages/shuttle/main/index.html). Once launched with the help of parallel rocket stages, the Shuttle would perform its mission in orbit (e.g. [deploying the Hubble telescope](https://www.nasa.gov/mission_pages/shuttle/shuttlemissions/archives/sts-31.html)), re-enter the atmosphere, and then land like an airplane. Despite its long lifetime, however, the Space Shuttle program (1981 — 2011) unfortunately [did not achieve launch prices competitive](https://www.space.com/12166-space-shuttle-program-cost-promises-209-billion.html) to those of single-use launchers. 

This essay will describe how spacecraft launchers work and will indicate some recent important developments in the launcher market. Along the way I will share my own forecasts indicative of spacecraft launchers' future. 

First, a [rocket operates based on Newton’s third law](https://solarsystem.nasa.gov/basics/chapter3-2/#rocket), producing thrust by expelling gas at high velocity. There are two types of rockets: In [liquid-propelled rockets](http://www.braeunig.us/space/propuls.htm#engine), a fuel (e.g. liquid hydrogen, kerosene) and an oxidizer (usually liquid oxygen) stored in separate tanks are combined into a combustion chamber. The resulting intensely energetic chemical reaction generates superheated gas which escapes through a nozzle, producing thrust. Liquid rocket engines are usually higher performance, throttle-able, and can be turned off and restarted. [Solid rocket motors](http://www.braeunig.us/space/propuls.htm#solid) store propellants in solid form. As with a match, once ignited they can't be turned off. Though lower performing than liquid propellant rockets, their operational simplicity and easier storability make them suitable for many applications.

Propellants make up [most of the weight of spacecraft launchers](https://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html), with the payload itself being only a small portion of the weight at launch. As the propellants are burned off during powered ascent, a larger proportion of the weight of the vehicle is taken up by the empty tanks and rocket structures. To make reaching orbit easier, most launchers are composed of multiple stages. Once a stage runs out of propellant it is jettisoned, thus relieving the rest of the rocket of the dead weight. 

There are two types of [rocket staging](https://www.grc.nasa.gov/www/k-12/rocket/rktstage.html), serial and parallel. In serial staging a smaller, second stage rocket is placed on top of a first stage rocket. The first stage is ignited at launch and burns until it runs out of fuel. When this happens, the second stage separates, ignites its engine, and brings the payload to the required orbit. In parallel staging, “strap-on” boosters are attached in parallel to a central rocket. At launch, all are ignited, with the strap-on boosters jettisoned when they run out of fuel.

There has been intensive development on reusable launchers during the past decade. Companies such as SpaceX are developing [reusable first stages and boosters](https://www.spacex.com/vehicles/falcon-9/), which can be recovered by performing a [guided descent and landing](https://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_development_program#/media/File:Falcon_9_First_Stage_Reusability_Graphic.jpg) after they boost the second stage and separate from it. The [proposition is not straightforward](https://pdf.sciencedirectassets.com/271447/1-s2.0-S0094576521X00100/1-s2.0-S0094576521003970/main.pdf?X-Amz-Security-Token=IQoJb3JpZ2luX2VjENX%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaCXVzLWVhc3QtMSJIMEYCIQDZc%2FeQz1WgY9vEmnF9jjoRwVWZxtAElYpSJavr1CabsAIhAMYmKM0f83voLQ7wjeYdDXW6azf2f2rGQPlXnU7ruekHKoMECL7%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEQBBoMMDU5MDAzNTQ2ODY1Igz5omnfU%2FtBBkrc%2F9wq1wPvmthbqp6wgEmaJMR77CYCJJFXPt9ZHoRiPyZJ7K9j8X8qZuY5gR2rs6WJIMF972uoWMAWVAytf8DTUC%2F9rsgqFvaUuMdWGId1h2ekCFXDU%2BGyU2Mvkr5EKf4AOUggOXNKvh3aORTh3qLMsXxVu%2F5HHsGNU6XN7OA5jQFsgEbepWmnYn6xnt0qJ%2BIrLEc2CdgMUA5POwNk8Zp5Rt4auJR9hKZ1jeCC69HWGmWdQZmwECuMJhuxa6qUMeqcb8yxC9xkeaQh24gUssWplGTIikJBiv3t9DfgTS0qijYvq6SeATj6y3HMP3332MIHVDQnAyHD%2F5sr9OEIdLORlmdARfM1%2B04ia7LxFbR%2BcaZhj6D2AXyLrrfp0vyd79nMU0kefop2cZFCXJHuFe2ZJTrdQv6N0MKsgHpFEOYie61qOZPEXBsmIlat4Xr9phz0ncLCScvS4sPMrnj76dGhLf5OqVjeQ1tfe%2BR6iEkecPgx5vUhvzj3i3yeCVCG2C9rDZiS3NnnZLIluuvmTYV5dzMkZ6b3BeQ38G%2BE7mz%2B9F6PiINdLUrxcr22LVbz9ByedwnYSo096faQQ4MdYaT5HQBORTJxvYCVER4SWQOJktOL2aXst7QG0%2B7VF8Yw47X3jQY6pAEdxRyzY4j0668bqESkbfF31UsiI7CYUjhAi3uTXvK8KLpDL2PIR4GTiopZTZ5lfCFGQkmJkR%2FEKAC6Moa3ZHQMRh9yQIWKi029TztE0a3ogj8fRM%2FLFeZ6E%2FLSX0IV%2FOv1c8ZvSJ0clO%2Btu4P2uHMjNJBrXhuv6K%2FnQLvCkIbrPS7iPBp6zZjIh1AfYmcO0vd4SK1Cp%2F1bpZ0Op5ZGoM21rskcqw%3D%3D&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20211218T131901Z&X-Amz-SignedHeaders=host&X-Amz-Expires=300&X-Amz-Credential=ASIAQ3PHCVTYVZNZ6VN6%2F20211218%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Signature=6cdb362f9a770fcb942d796f7510fd672142d26e9c5c007ef981e799e51d5009&hash=14befa0d3bbfdc5d83818fb47bc9c7425e1713c2b0e483a30690579f1c4034b3&host=68042c943591013ac2b2430a89b270f6af2c76d8dfd086a07176afe7c76c2c61&pii=S0094576521003970&tid=spdf-ed62a37b-f0ec-4ce9-84d1-0076ed9216dd&sid=9c76fb9e8d5c33454e782857ccedd0b76456gxrqb&type=client): Additional fuel must be reserved for this maneuver, and the technologies necessary for reliable and accurate autonomous landing are not simple. SpaceX, however, has demonstrated the reliable recovery of first stages and is currently [moving toward routine reuse](https://www.nasa.gov/sites/default/files/atoms/files/space_portal_edgar_zapata.pdf). Plans for a reusable second stage have been scrapped due to the high technical difficulty of returning practically from orbit. The [Starship concept](https://www.spacex.com/vehicles/starship/) has become the mainstay for SpaceX for a reusable second stage and is meant to be part of a fully recoverable launcher system.

So far, we have focused on multi-stage launchers. However [single-stage-to-orbit](https://en.wikipedia.org/wiki/Single-stage-to-orbit) (SSTO) vehicles would be technically possible. Such a vehicle would provide a significant launch cost decrease by eliminating the costs associated with using different stages, reusable or not. Several SSTO designs have been proposed over the years, including [rocket-based,  air-breathing](https://scholar.afit.edu/cgi/viewcontent.cgi?article=4552&context=etd), [nuclear-powered](https://arc.aiaa.org/doi/pdf/10.2514/6.2015-3958), and [jet-engine-powered](https://www.wired.com/story/the-rocket-motor-of-the-future-breathes-air-like-a-jet-engine/) vehicles. The main challenge for SSTOs is producing the necessary engine performance while at the same time drastically reducing structural weight and reliably delivering a meaningful payload in orbit. Recent advances in materials and engine development might bring SSTOs [closer to eventual implementation](https://www.colorado.edu/faculty/kantha/sites/default/files/attached-files/70494-96876_-_kyle_borg_-_may_8_2015_853_am_-_borg_matula_skylon_report.pdf).

Several less conventional methods for launching payloads into orbit [have been proposed](https://arc.aiaa.org/doi/10.2514/1.46148) over the decades, including [nuclear powered rockets](https://www.energy.gov/ne/articles/6-things-you-should-know-about-nuclear-thermal-propulsion), [beamed energy propulsion](https://www.colorado.edu/faculty/kantha/sites/default/files/attached-files/72875-96876_-_nishant_agarwal_-_may_7_2015_532_pm_-_rocket_propulsionfinal_report.pdf), [electromagnetic or gas guns](https://ntrs.nasa.gov/api/citations/20110005535/downloads/20110005535.pdf), and the momentous [space elevator](https://www.nbcnews.com/mach/science/colossal-elevator-space-could-be-going-sooner-you-ever-imagined-ncna915421). These concepts are currently relatively immature; however SpinLaunch [recently tested a prototype](https://www.space.com/spinlaunch-first-test-flight-success) centrifugal “gun” for launching payloads.

The space launcher market [has been and arguably still is](https://link.springer.com/chapter/10.1007/978-3-7091-4860-0_12) in a quasi-commercial state, with a monopoly or an oligopoly of launch providers often matched by a monopsony (single-buyer) from governments. Moreover, governments subsidize and buy from providers based not only on market but also political considerations, such as strategic independence and economic development. The current relative dynamism in the launcher market [can arguably be traced back](https://www.frstrategie.org/sites/default/files/documents/publications/autres/2017/2017-wohrer-these.pdf) to the difficulty of American launchers to keep up with the reduced prices and increased reliability offered by the European Arianne launcher in the first decade of the 21st century—and the further reduced prices offered by Russian, Chinese, and Indian launchers. 

During the last decade, SpaceX has further reduced prices and has become a leader in the market. This includes payloads requiring high performance, e.g., those that are national security-related or for the human spaceflight program. Initially it would appear that this price reduction can be attributed to the impressive and much publicized developments in reusability that SpaceX has developed. It has been argued, however, that the dominant driver in this price drop [is not technical, but is instead the result of institutional and cultural effects](https://ttu-ir.tdl.org/bitstream/handle/2346/74082/ICES_2018_81.pdf?sequence=1&isAllowed=y), i.e., the trio of lean manufacturing, vertical integration, and flat management. To these can be added the [implicit subsidies](https://link.springer.com/chapter/10.1007/978-3-7091-4860-0_12) by the US government for strategically important payloads. Other launch vehicle companies are reacting to SpaceX’s takeover of the market, with, for example, Ariannespace restructuring and aiming to [integrate reusability for its launchers](https://www.esa.int/Enabling_Support/Space_Engineering_Technology/ESA_plans_demonstration_of_a_reusable_rocket_stage). 

High launch costs have been a bottleneck for space utilization. The current high cost of reaching orbit means that satellites must be built to maximize their yield per kilogram and their reliability. Lower launch costs would allow satellite designers more freedom and could encourage more innovative solutions, eventually even bringing [economies of scale to the space market](https://link.springer.com/chapter/10.1007/978-3-7091-4860-0_12). With the recent developments in the launcher market, we might be on the cusp of a benevolent cycle that will significantly increase the use of space and its benefits to mankind.