Hot answers tagged

71

Hobbes' answer focuses on why we might want to build SLS. There are also significant barriers to rebuilding Saturn/Apollo. In addition to the (vast) amount of existing technical documentation on those designs, there's a (probably vaster) pool of knowledge that the individuals who actually built the things collected during the process. Nearly all of those ...


56

One of the keys to SpaceX's cost advantage is standardization on common parts. One example is the Merlin engine, which is used on both the first and second stages of the Falcon 9 and Falcon Heavy (though a slightly different vacum optimized version on the second stages). This is also done for fairings. Fairings are very expensive to make (around $6M). ...


47

Preface: I am far, far from an expert in space electronics; I don't think I can weigh in on how much these sensors actually are, which is the title question; all I can offer is an uneducated inane ramble on where that money might be going. Let's take your analogy of a bargain-basement thermal sensor; actually, let's specify a common off the shelf Melexis ...


38

There are several reasons: We can do better these days. Saturn and Apollo were designed in the early 1960s, so the design tools used were mainly pen and paper, with some primitive computer tools thrown in here and there. These days CAD can be used to create a design that performs far better (because you can design parts closer to the strength they need, ...


28

NOTE All dollar values are in present day values accounting for inflation. Another reason we're not reusing the Saturn V is the same reason it was cancelled in the first place: cost. The SLS is supposed to be half the cost per launch. Whether that works out remains to be seen. The Saturn V was expensive. The Saturn V program cost \$47 billion over 10 ...


28

This is due to a variety of reasons which I will detail further down in my answer, but let me first correct a few of the points you raise. Corrections Contract Awarding These contracts represent the amount of funds requested by each company, and is essentially their "bidding price" for the services they can provide. NASA then selects companies from those ...


28

Ars Technica has a pair of articles that give some insight in why it's desirable to use new designs: NASA has been working on an updated version of the F-1 (the first stage engine for the Saturn V). Some of the major differences: Another clear difference is the construction of the exhaust nozzle itself. The F-1's nozzle was made up of two parts: the ...


28

I'll chime in with the other two well-stated answers. In addition to all the testing, there is the issue of "What do you do when the instrument fails a test?" Most COTS (Commercial Off-The-Shelf) instruments you might get at Home Depot or even Omega Engineering are designed to work in an Earth environment, with some margin. But not too much margin; that ...


24

Has anything been "built" in space before? Absolutely. Perhaps not "built" in the sense you're talking about, but certainly assembled. A sterling example is the International Space Station. There are about a dozen distinct modules in the ISS that are pressurized and fit for occupation. The first was Zarya, and the latest is Leonardo. They've been ...


23

Three big factors: The energy required is large (http://en.wikipedia.org/wiki/Specific_orbital_energy). For a low orbit like the one the ISS is in, it's about a 33 MJ/kg addition from the surface to orbit -- and that neglects atmospheric drag. The rocket equation (http://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation). In a nutshell, you must not only ...


22

A 3D printer on station isn't likely to lead to direct cost savings; the range of items it can replace are limited, and it has to be supplied with feedstock mass in any case; it won't allow for significantly fewer supply launches. The primary benefit is that it can allow for the repair of a system the astronauts would otherwise have to do without until the ...


22

Necessarily speculative, but here goes... Let's look at what "the initial concept" really was. The post-Apollo vision was to build space infrastructure that would enable the manned exploration and exploitation of the solar system. The surface-to-low-Earth-orbit reusable shuttle was but one part of this grand plan, as shown in this 1970 slide from Marshall ...


21

Yes, humans definitely have been to outer space. The easiest proof I can think of immediately is this video of commander Chris Hadfield demonstrating wringing of a wet towel on the ISS. Or this one — it contains more than 200 seconds long uncut shot of a̶b̶s̶e̶n̶t̶ micro-gravity. It also shows vast interiors of the ISS, which are technically challenging to ...


21

Yes, it is unfortunate that the space station is not quite fully in space. It is in Earth's upper atmosphere, which is why it requires such frequent reboosts. From this Wikipedia entry: The ISS requires an average 7,000 kg of propellant each year for altitude maintenance, debris avoidance and attitude control. ... Multiple supply vehicles are ...


21

As Mike Wise elucidated in his comment, this is rather speculative, since SpaceX as a private company can (and do) choose to keep their cost structures and breakdowns secret, and the prices vary between launches. We can, however, use a few bits of information to get a coarse overview of the prices involved. Customer-facing costs SpaceX currently sells an "...


21

The EU and ESA are not related. They have different member states, where neither is a subset of the other. The only potential issue is simply economic. If the British exit from the EU results in a depressed UK economy, then they may elect to participate less in ESA.


21

Okay, this is misleading. They received beyond their normal salary the government Per Diem, which amounts to $8/ day. Also, this was reduced somewhat because they didn't need to pay for their sleeping locations. This is the same as any government travel, if they were traveling in a location where they didn't need to pay for their housing, they didn't receive ...


20

1.87 km/sec Δv between low lunar orbit and the surface. Thus you need 3.74 km/sec plus some reserve because suicide burns are for KSP, not real life. To make a trip from low Earth orbit to low lunar orbit is 4.04 km/sec Δv and I believe the return is 1.40 km/sec Δv. Thus your total Δv is 5.44 for the trip to low lunar orbit (and less if you go to a higher ...


20

The cost depends on the rocket, and on the percent capacity of said rocket, but here's a few numbers for you, cost in U.S. dollars/kg to LEO (Wikipedia*). It should be noted that not all rocket prices are publicly available, in fact, most aren't. Falcon Heavy: \$2200 Falcon 9 v 1.1- \$4,109 DNEPR- \$3,784 Ariane 5- \$10,476 Delta IV- \$13,072 Atlas V- \$13,...


20

I realize that the equipment is awfully expensive and probably takes a small army of people to maintain, but that still boils down to a few thousand dollars per hour of radio time ... The cost in 2017 dollars ranges from \$954 per hour of contact for use of a 34 meter High-Speed Beam waveguide antenna to \$4770 per hour of contact for use of a 70 meter ...


20

With current technologies, this is unfortunately well outside our reach. However, there is promise on the horizon! Chemical Engines The Tsiolkovsky equation is always your friend when calculating Δv for conventional engines (or your enemy, depending how you look at it!): $$ \Delta v = I_{sp} \times g \times \ln \frac {Mass_{full}} {Mass_{dry}} $$ ...


18

The problem here is that your standard of proof is ridiculous. By the same token, you'd have to doubt the existence of Moscow because you've never met anyone from that city. the only face to face eyewitness event that I can remember where humans actually observed an attempt to fly into outer space... Then your memory must not be very good. There have ...


18

The 3-D printer on the ISS is more for testing purposes than anything. The idea is that for really long duration missions, a 3-D printer will allow them to make something in case something breaks, or they realize they need something that didn't come initially with the ship. So far I can only find a few things that have been made, including a ratchet, several ...


16

Jack did a great job describing how to do it using propulsive engines. I have a different answer: We already (almost) planned to do it (inadvertently). The original plan for the recently launched Parker Solar Probe was to do a gravity assist at Jupiter for a subsequent fly-by of the Sun at a relative speed of more than 300 km/s. So, to get to a speed of ...


15

Here is a basic rundown of the effects of the shutdown: 97% of NASA was furloughed. That is the highest percentage of any agency listed. The only known NASA direct operations are those related to Mission Control, and astronauts on the ISS. Everything else was shut down completely. JPL and APL are technically NASA contractors. This is really good news as ...


15

The number of actual collisions with orbital debris is incredibly low, all things considered. (Number of actual debilitating impacts vs number of active satellites divided by time. Odds are very very low). Sure flecks of paint have hit the Shuttle and ISS, but really a very small number of actual collisions causing damage, to a fairly large number of ...


13

Per https://standards.nasa.gov/documents/viewdoc/3315318/3315318 . NASA Policy Directive COMPLIANCE IS MANDATORY NPD 1210.1G Effective Date: April 28, 2010 Subject: Acceptance and Use of Monetary Gifts and Donations Responsible Office: Office of the Chief Financial Officer POLICY The National Aeronautics and Space Administration (NASA) may accept and ...


13

When the amount of evidence, circumstantial or direct, for a given proposition vastly outweighs evidence against that proposition, most reasonable people are willing to accept the proposition as true. This does occasionally lead to having to change your mind about a proposition when new evidence comes along; this is how the scientific method works. In the ...


13

Yes. And even worse, there are no planetary launches planned in 2017, 2018, or 2019! Zero. Zippo. Nada. As you can see from the Planetary Society plot, this is due to not having such missions in planning in several preceding years. Here is the source of the graphic with some more information.


13

First of all, let's figure out how many satellites per launch vehicle. The estimate of the mass of these satellites is 386 kg. The mass for a launch of a Falcon 9 is 5500 kg. That means one could launch 13-14 satellites per rocket. I suspect 12 is more realistic, because part of the payload mass is the structure to mount all of the satellites, and that is ...


Only top voted, non community-wiki answers of a minimum length are eligible