Editing Rocket engine (section)

====Solar thermal====

The [[solar thermal rocket]] would make use of solar power to directly heat [[reaction mass]], and therefore does not require an electrical generator as most other forms of solar-powered propulsion do. A solar thermal rocket only has to carry the means of capturing solar energy, such as [[Concentrating solar power|concentrator]]s and [[mirror]]s. The heated propellant is fed through a conventional rocket nozzle to produce thrust. The engine thrust is directly related to the surface area of the solar collector and to the local intensity of the solar radiation and inversely proportional to the ''I''<sub>sp</sub>.

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Solar thermal rocket]] 
| Propellant is heated by solar collector
| Simple design. Using hydrogen propellant, 900 seconds of [[specific impulse|''I''<sub>sp</sub>]] is comparable to nuclear thermal rocket, without the problems and complexity of controlling a fission reaction.{{citation needed|date=January 2011}} Ability to [[Solar thermal rocket#Proposed solar-thermal space systems|productively use]] waste gaseous [[hydrogen]]—an inevitable byproduct of long-term [[liquid hydrogen]] storage in the [[Radiative heat transfer|radiative heat]] environment of space—for both [[orbital stationkeeping]] and [[Spacecraft attitude control|attitude control]].<ref name=aiaa20100902>{{cite web|last=Zegler|first=Frank |title=Evolving to a Depot-Based Space Transportation Architecture |url=http://www.ulalaunch.com/site/docs/publications/DepotBasedTransportationArchitecture2010.pdf |archive-url=https://web.archive.org/web/20110717150155/http://www.ulalaunch.com/site/docs/publications/DepotBasedTransportationArchitecture2010.pdf |url-status=dead |archive-date=2011-07-17 |work=AIAA SPACE 2010 Conference & Exposition |publisher=AIAA |access-date=2011-01-25 |author2=Bernard Kutter  |date=2010-09-02 }} See page 3.</ref>
| Only useful in space, as thrust is fairly low, but hydrogen has not been traditionally thought to be easily stored in space,<ref name=aiaa20100902/> otherwise moderate/low [[Specific impulse|''I''<sub>sp</sub>]] if higher–molecular-mass propellants are used.
|}