# Tag Info

63

A big difference is that you wouldn't need to leave someone in lunar orbit. We now have experience and confidence in the remote operation of an uncrewed vehicle. So you could have a crew of two instead of three. Or perhaps a crew of three to the surface with a larger LM. Overall, there would be much more automation, especially for the landing process, ...

50

The short answer is it would cost a lot of money. In order to get a 1G force, you'd either need something really big, or rotating very fast. For example, the reference design for the space colonies I'm working on calls for a structure with a 900 meter radius rotating once a minute. For something the size of the ISS, it would have to be rotating much ...

45

Yes, there are people whose sole job is "mission design." They design the trajectory that a spacecraft should follow to fulfill its mission and all of the maneuvers needed for that to happen. Some companies specialize in mission design consulting, like Space Exploration Engineering, Advanced Space LLC, or the X Team from JPL (although the latter ...

37

This mission study came up with a 900 kg nuclear-electric-propulsion spacecraft launched on an Ariane V with a C3 of 100 km2/s2 and a Jupiter gravity assist along the way. 1.05 kW electrical power at Pluto from RTGs is required. That would be four "classic" NASA RTGs, or about nine MMRTGs. It has a 20 kg science payload. (New Horizons has ~30 ...

35

The drop in acceleration around 40s into the flight is the shuttle throttling down to reduce the aerodynamic load on the vehicle. It then accelerates when past this point. The drop in acceleration at 2 mins into the flight is due to the solid rocket boosters running out and being discarded. Acceleration then continues to build, as the thrust from the engines ...

34

I do not think your assertion that "other rockets were just as capable of performing the task at that time" is correct at all. I'd love to hear your counterexamples, if you have any. Perhaps you are referring simply to their payload-to-LEO capability? If so, that is only the tip of the iceberg. No other vehicle at the time provided all the elements of EVA ...

34

A lot of launch costs are independent of rocket size. It's no cheaper to clear the flight path for a smaller rocket, for example. It also takes a lot longer to do 10 launches instead of one large launch, and spaceflight is full of cases where you have limited launch opportunities. A larger vehicle will have higher throughput and lower costs per kg. Smaller ...

32

The long distance to the Sun mandates long exposure times. The New Horizons spacecraft needs to be relatively stable and its pointing accurate throughout these long exposure times. New Horizons does not have a scan platform. The cameras and other science instruments are fixed with respect to the vehicle. The satellite has to turn as a whole to keep the its ...

32

Launching and assembling the ISS in its current design could not have been accomplished without the STS (Shuttle system), but that is largely because the ISS was designed with the STS in mind as its launch vehicle. The ISS could be designed to be assembled in orbit using a large number of spacewalks because designers knew they would have the shuttle ...

31

This was one of the questions just now during the Rosetta press briefing. This video was shown during the presentation: The triangular trajectory are hyperbolic orbits with respect to the comet and they'll (also, among other tasks also mentioned in the image you're attaching) serve to establish its mass. In essence ...

29

The diagram you show is the digital version of a drawing by someone with an Etch-a-Sketch: completely inaccurate. The diagram below is accurate, showing Pioneer 10 & 11 and Voyager 1 & 2 trajectories in a heliocentric, inertial reference frame, of course with the ecliptic N-S dimension collapsed. No retrograde, no dog-legs between planets. Every now ...

29

A solar sail with an areal density of $1~\mathrm{kg}/\mathrm{km}^2 = 1~\mathrm{mg}/\mathrm{m}^2 =0.001~\mathrm{g}/\mathrm{m}^2$ is impossible by known materials science because graphene has an areal density of $0.77~\mathrm{mg}/\mathrm{m}^2$. Being a single atomic layer of a light atom, graphene is the absolute lower bound for the areal density of pretty ...

28

Space is basically a vacuum, so there's no air resistance. A probe that's been launched will travel at the same speed indefinitely. Because New Horizons is moving away from the Sun, it loses some speed to overcome the Sun's gravity. New Horizons was launched on the fastest rocket they could get. Then it used a gravity assist from Jupiter to gain some more ...

27

In order to use the direct ascent method of landing on the moon, which is where the entire vehicle descends and leaves the moon, you would need a rocket an order of magnitude bigger than the Saturn V, not just a bit bigger. Here's an early comparison NASA made back before they decided to use Lunar Orbit Rendezvous: The C1 became the Saturn I, the C-5 ...

26

The uncrewed Surveyor probes landed on the moon before Apollo did. They provided visual images of the landscape and pictures of soil samples that were dug up robotically. All the visual indications were that the terrain was fairly firm: Surveyors also took pictures of their own footpads to see how deep they went into the soil: The ground pressure of the ...

26

Ulysses, the shuttle-launched joint NASA/ESA probe to study the sun's polar regions, ran through three comet tails, more or less by chance. Ulysses Catches Record for Catching Comets by Their Tails ...comet Hyakutake ...On May 1, 1996, while Ulysses was cruising through space studying the solar wind, its data suddenly went wild for a few hours. The once-...

25

Dawn has several mission objectives, including to continue testing the Ion Thruster. But why Ceres? Ceres and Vesta were chosen, because they have contrasting content, one icy and one rocky. Also, they are among the protoplanets that remain intact since formation, which (hopefully) leads to a better understanding of the formation of our solar system, ...

23

This is probably the easiest to answer if we take the same mission profile and just track from the Pluto flyby backwards. I'll make some rather broad assumptions and first order approximations, like that NASA had their NEXT ion thruster developed to the highest technology readiness level (they did exist when New Horizons launched, but not at TRL required to ...

23

If you want an example manifest for one logistics flight, that's available. Search terms...suggest "ISS Cargo Manifest" From SpaceX 2 Cargo Manifest (see link for details) 81 kg of crew supplies (food, clothes, paperwork) 25 kg of international partner experiments 323 kg of NASA experiments 3 kg of EVA tools 135 kg of ISS hardware 8 kg of PC parts ...

22

While many missions have been able to continue beyond their design lifetimes (Cassini and the Mars Exploration Rovers being prominent examples), the type of mission and orbit Juno must undertake to accomplish its goals will subject the spacecraft to a truly massive radiation dose. In order to meet the mission’s science goals within the budget set by NASA, ...

22

Propulsion Until someone solves the N-body problem every spacecraft needs some kind of propulsion to correct its course during the mission. New Horizons uses a Hydrazine based propulsion system including four 4.4 N main thrusters and twelve 0.9 N attitude control thrusters. Its 77 kg fuel tank allows a total post launch delta-v of somewhere over 290 m/s (...

22

Since you have tagged the question apollo-program, I will explain the Apollo era consoles. Sources are from this Ars Technica article, which interviewed flight controller Sy Liebergot. The flight controllers' consoles were "dumb"—they contained no computing elements and just displayed what came in from the mainframe. In the Apollo era, the consoles ...

21

The STEREO satellites used multiple gravitational assists from the Moon to significantly decrease the amount of fuel needed to put those two satellites into heliocentric orbits. The first flyby resulted in STEREO ahead (STEREO-A) being ejected from the Earth-Moon system with a semi-major axis slightly less than that of the Earth-Moon system. STEREO-A has a ...

21

During the early part of the Apollo program, the "direct ascent" mode was favored and Lunar-orbit rendezvous (LOR) was considered far too complex. In fact, the specifications of the Apollo service module were set by the direct ascent plan: the SPS engine is sized to lift off from the moon, and the fuel tankage is sufficient for lunar ascent and return to ...

21

Power and Mass From this paper (emphasis mine): The specific power of an 241Am-fuelled RTG cannot match that of a 238Pu system (except perhaps at small power output levels); however, the design work undertaken provides confidence in potential capability and performance of 241Am systems for future space missions. Medium-sized RTGs in the 10 W to 50 W range ...

20

The first, experimental redocking was performed on Soyuz 29 (though by crew of Soyuz 31) with the Salyut 6 station. Afterwards, the maneuver was repeated several times, usually between different ports of a station, moving a docked craft from one port to another, in order to make room for a new arrival, although other purposes happened too - e.g. visual ...

20

Are launch windows to Mars avoided if they result in landings during dust storm season? No. It's pretty well known that the gusts of wind on Mars are relatively harmless to a person standing on Mars (one of the big things the movie The Martian got wrong). Even though winds on Mars could reach up to 130 km/h, the atmosphere is very thin and thus does not ...

20

There is a extensive summary report on possible improvements of solar sail materials: "Ultra-Thin Solar Sails for Interstellar Travel - Phase I Final Report" December 1999, Dean Spieth, Dr. Robert Zubrin When reading this report one has to keep in mind that they only look for the properties of the sail itself, not taking into account structural ...

19

There's an assumption in your question. the Apollo configuration of 3-person CSM and 2-person LM, launched atop a single vehicle was considered the optimal choice for its day. The simplest mission profile would have been a direct flight. The docking required for both EOR and LOR schemes seems to have been distrusted at the time; hence a major objective ...

19

Not very quickly, for a number of reasons. Here's a list of some of the reasons: Soyuz requires 2 astronauts just to fly it (Under nominal operations) It can only take down 3. Thus, 6 Soyuz launches would be required. (Note, this might be a reference to manned flight, Soyuz does have remote capabilities). Some work could probably be done to reduce that to 1 ...

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