Previous: Chapter 1 - Heat and Radiators

Chapter 2: Science

This chapter of the Illustrated Guide to KSP Interstellar will cover the science experiments that Interstellar offers in the early to mid-career, before nuclear power or advanced engines. Some are in the traditional mold of go to place, activate sensor, receive science, but some are more interactive.

Seismic Impactor Experiment

In addition to measuring natural vibrations and impacts, the seismic sensors placed by the Apollo landings were used to measure the impacts of several discarded S-IVB upper stages and Lunar Module ascent stages. The known characteristics of the impactors aided scientists in interpreting the seismic readings to draw conclusions about the structure of the Moon and the nature of other impacts.

Interstellar modifies the stock Double-C Seismic Accelerometer to remove the stock experiment that could be performed whenever a craft is landed, and replaces it with an experiment that requires you to provide impacts to analyze.

Placing seismic sensors

Land a sensor anywhere on the surface of the body of interest, right-click it, and select "Record seismic data" to begin monitoring.

For the best possible science yield, land multiple sensors at different points on the surface. Five sensors spaced about 90 degrees apart will be enough to achieve maximum science.

Data on active sensors is stored in WarpPlugin.cfg in your save folder. The data is associated with the internal ID of the vessel, so if you jettison a sensor from a ship you will need to stop and restart it afterward. For instance, I like to equip the descent stage of each lunar module with a probe core and a seismometer. When the ascent stage departs, the vessel ID that the combined lander had before separation generally refers to the ascent stage, so I've found it necessary to start recording only after the ascent stage has departed and the descent stage has had its final vessel ID assigned.

Performing an impact

Once all probes are recording, switch to the ship or debris that will impact. I left a transfer stage in orbit with a probe core on it so I can direct it to impact at my convenience.

The impactor doesn't need control or engines; any old piece of debris will do if you can arrange to jettison it on a trajectory that will impact after you've landed. If the impactor is very small, it may have too little impact energy to produce usable data. Comments in the source code indicate that the intended threshold is 800 kJ (a 1-ton mass at a vertical speed of 40 m/s or equivalent), but I've noticed some potential bugs in the code that will need further testing to confirm. I don't advise relying on the exact numbers here; if a small or low-speed impact doesn't register, try a larger or faster-moving impactor.

If the impact passes the checks, a message on the screen will inform you that the science is ready to collect.

Collecting the data

As the message suggested, switch to one of the vessels that was recording on the body you impacted, right-click the seismometer, and select "Collect impact data." A standard result screen will appear from which you can transmit the data or collect and return it as you would with a stock experiment.

One "Collect impact data" will collect all uncollected data for that body; even if you have multiple sensors deployed, you can collect the science from any of them without visiting all of them.

One impact has a base value of 50 science, with a multiplier for the difficulty of the body as shown on the table below. The value is halved for each successive impact on the same body.

Body	Multiplier
Kerbin	0.5x
Mun/Minmus	5x
Duna/Ike/Eve/Gilly	7x
Dres	8x
Tylo/Pol/Bop	9x
Laythe/Vall	11x
Eeloo/Moho	14x

Multiple sensors on the same body provide another multiplier of up to 3.5 times the value of a single sensor. The exact multiplier is calculated based on the number and spacing of the sensors. This is another mechanic where I advise against worrying too closely about the exact numbers. As long as you keep the maximum in mind for its effect on possible transmit sizes, exactly where a particular grid falls between the base and the maximum multiplier is rarely important.

The science result transmits at 100%, but the file size is larger than most stock experiments and may be inconvenient if you're not expecting it. Transmitting uses ElectricCharge faster than solar panels or RTGs provide it, so transmitting a large file without interruption requires significant battery capacity. Later, nuclear-powered spacecraft will have an easier time because the reactor will generally be able to keep up with the power demand of transmitting.

Each seismic result has a file size of 2.5 Mits per science, so more valuable data is more demanding to transmit. A first impact on the Mun with one sensor active is worth 250 science. At 2.5 Mits per science, the transmission will be 625 Mits. The Communotron 16 I'm using draws 5 EC per Mit, so to avoid interrupted transmissions I've made sure I have at least 3,125 battery.

If you need to transmit a result that exceeds your battery capacity, you can take advantage of the fact that time acceleration applies to the rate of electricity generation, but not to the transmission rate. As you time accelerate, packets will be transmitted at greater intervals on the game clock, giving the batteries time to recharge between packets.

Space Telescope

Interstellar includes an infrared telescope to observe objects outside the local solar system without the need to compensate for the effects of a planet's atmosphere. Space telescopes have a particular advantage in the infrared range of the electromagnetic spectrum because water vapor strongly absorbs many of these wavelengths.

When the part is unlocked, one experiment is feasible: a deep-field survey in which observations of the same area of sky over an extended period of time are integrated to reveal details that could not be resolved in a single exposure.

This telescope is a tubeless design resembling a smaller, rigid version of NASA's in-development James Webb Space Telescope, but cooled with liquid helium like current telescopes. The liquid helium that it requires to run is stored in a cryostat that must be connected to the telescope by stack attachment or fuel lines as you would a fuel tank. Helium coolant gradually boils off and must be resupplied to keep the telescope operating long-term.

Each liquid helium cryostat requires 8 kilowatts of electricity to provide cooling. If power is interrupted and the cryostat loses active cooling, the helium supply will boil off much faster. You may recall from the previous chapter that 8 kilowatts is the maximum budget of a ring of four OX-4Ls when they are perfectly oriented and unobstructed. Since perfect orientation is next to impossible to maintain and the spacecraft will have other power demands on it as well, I've opted for a pair of the 18 kW Gigantor XLs. 36 kilowatts of maximum power means 18 kilowatts maximum heating, which is still within the capability of the two small radial radiators. Eclipse time in 100km LKO is 642 seconds, so I have 5,400 battery to ensure that I can keep the cryostat cold all night. A docking port at the other end of the stack permits supply and servicing.

Once you have reached a stable orbit, right-click the telescope and select "Deep Field Survey" to begin collecting data. In Kerbin orbit, the telescope produces data worth 0.17 science per Kerbin day. Telescopes in other spheres of influence are worth greater amounts. Leave the telescope in orbit for a few days, head back to the space center, and fly any other missions you have in the pipeline.

When the telescope has been running for a few days, come back to it, right-click it, and click "Deploy" to collect the accumulated data. Note: The text "Deploy" is a bug; in future versions of Interstellar this will likely read "Collect Telescope Data."

This will generate an experiment result with a value based on how long the telescope has been running and where it is located, which you can then recover or transmit in the usual manner. Transmission size is 1.25 Mits per science.

Servicing the telescope

As the telescope runs, the helium coolant in the cryostat will boil off, and the "Performance" listed in the context menu will go down. Performance acts as a multiplier to the science generation rate, and when the helium supply is depleted the telescope will cease to function at all.

A servicing mission can dock with the telescope and transfer additional helium, and a kerbal on EVA can right-click the telescope and "Perform Maintenance" to restore the performance multiplier to 100%.

These maintenance requirements create a trade-off. A telescope orbiting Kerbin produces science only slowly, but is easy to maintain. A telescope in a more remote orbit outside Kerbin's sphere of influence will produce science faster, but you may find yourself with a telescope in need of servicing and no way to reach it before it shuts down.

Resource scanning experiments

Some of the instruments that we will use in future chapters to detect harvestable resources can also supply science.

The Dual-Technique Magnetometer can run as an experiment in low or high orbit. Without biome sensitivity, it makes only a small contribution to the science totals that other experiments offer at a similar stage of the game. It's still one of my favorite experiments because the boom has been such a prominent feature of iconic real-life probes.

The Gas Chromatograph Mass Spectrometer that measures atmospheric resources can also run as a science experiment. It will operate on the surface, lower atmosphere, or upper atmosphere of any body with an atmosphere and is not biome-specific.

Despite its similar appearance, the Liquid Chromatograph Mass Spectrometer lacks a science experiment.

Coming soon: Chapter 3 - Nuclear Power