Hiatus

There is a going to be a pause now, a break in spacewordgame. Depending on a host of factors, it may resume shortly, or not.

Thanks!

Maria

Maria are the plural of mare. A dark, flat, large region on the surface of the Moon. The term is also applied to the less well-defined areas on Mars. Although maria literally means “seas,” watery regions do not exist on the Moon or Mars. Marias on the Moon and elsewhere may be evidence of past volcanic lava flows. 

Ablative

Ablative means 'able to be eroded or flaked away'. An ablative heat shield is one in which the shield material itself vaporises and takes the heat away with it as it goes. The Apollo command module used an ablative heatshield made of a resinous material held in an aluminum honeycomb, and most entry and reentry vehicles use some form of ablative aeroshell in the same way.

Catadioptric

Referring to an optical system which uses both reflection (mirrors) and refraction (lenses). This also describes the unwanted effect of lens elements reflecting images inside a compound camera lens. Undesirable catadioptric effects include ghosting and lens flares.

Cislunar

Cislunar comes from the Latin, and is just a handy way to refer to all the space between the Earth and the Moon.

Cislunar Transfer

Ullage

This is almost a second part to 'bladder'. Ullage is the volume in a closed container which is not occupied by the stored material, such as fuel. Its also sometimes used to refer to a manoeuvre deliberately to move floating fuel in a tank to the tank exit pipe. Dedicated ullage thrusters have been used during the Saturn IV-V era.

http://www.astronautix.com/craft/blo1s861.htm

Retrograde

Retrograde means contrary to the normal direction of motion or rotation. A retrograde orbit is one that goes in the opposite direction of the rotation of the body being orbited. A retrograde manoeuvre opposes the direction of travel. Weirdly, 2 of the planets in the solar system have retrograde motion (on their own axes): Venus and Uranus. Venus' axial tilt is 177 degrees, so its spinning almost exactly in the opposite direction to its orbital rotation.

Reseau

A reseau is a grid of points or marks placed in a photograph by a transparent plate very carefully and precisely aligned with the camera's optics. This provides a stable and reliable basis for measuring objects in a photograph and for detecting and correcting distortions in the photograph. The Hasselblad cameras used on the moon were fitted with reseau plates.

Reseau grid crosshairs just visible in the famous Aldrin shot

Bladder

Bladders ought to be a fairly familiar concept, a stretchy membrane for containing fluids/gases. Bladders are relevant to space technology because they are used inside fuel tanks for at least 2 good reasons. Firstly, they confine the fuel into a volume roughly equal to the volume of fuel remaining, which prevents it from sloshing around and causing disturbances to the attitude control or GNC systems. Also, in a microgravity environment, it means you can keep the fuel in a partially filled tank close to the exit valve so you can use it. Easy really. Check out this page from Astrium about their bladder tanks.