# Tag Info

46

LAGEOS satellites This has, in a way, already been done, with the Laser Geodynamics Satellite (LAGEOS) satellites. LAGEOS satellites, (the second of which was launched from the shuttle on mission STS-52), have a projected orbital lifetime of over 8 million years. They are in a very stable medium Earth orbit. They are completely passive, but are ...

43

NASA have deployed 4 rovers to Mars, and are working on the fifth. ESA is working on nr. 6. Sojourner: tiny, limited. Spirit and Opportunity (MER): much larger than Sojourner. No reuse possible. Spirit and Opportunity were identical. Curiosity: much larger than MER. No reuse possible - but it does use technologies proven on MER, like the suspension design. ...

42

From STS-3, the tank was left unpainted, the brown color is the natural color of the insulation foam, see this PDF. The color would get darker from exposure to the sun. The tanks of STS-1 and 2 were painted white, but this took several hundred kg of paint, and after STS-1 and 2 tests showed that the paint wasn't necessary.

39

Neither has much financial purpose without the other. A BFR cannot perform any useful function without an upper stage, and that is the BFS. Since the whole platform is a major investment in a new architecture, they are starting with the smaller piece - the BFS. Since it uses some of the same engines as the BFR, it can act as a testbed for both BFR and BFS ...

29

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 ...

29

Elon Musk stated in a news conference after the Falcon Heavy launch that the BFS will be the focus because they think they understand designing booster rockets pretty well, and thus they decided to focus on the more difficult piece first. He answers this in response to a question that starts at 20 minutes 52 seconds here, and speaks specifically to starting ...

26

For supersonic flow, the Sears-Haack body offers less drag than the shorter teardrop that's optimal in the subsonic regime. Sears-Haack is pretty similar to the German V-2 rocket body. (Note that the proportions of this particular example aren't part the definition of the Sears-Haack shape; for minimal drag you'd have to have an impractical body of infinite ...

26

Has any research into actually producing anything larger than the F1 been seriously carried out? The M-1 was a hydrogen engine just a little larger than the F-1. Parts of it were built and tested and the engine would likely have worked just fine if completed and flown. Lack of need for a super-heavy lift vehicle larger than a Saturn V prevented it from ...

25

The problems would be many to transmit a radio signal for 10,000 years. However there is nothing about a 10,000 year lifetime that would violate physics. It would just be extremely difficult engineering. I would use a thermally driven Stirling engine for power, magnetic torquer for attitude control, and vacuum tubes for the electronics (which are much more ...

24

I think you answered your question in the first sentence. I am reminded of this image: Aerodynamics is but one (albeit a large one) of many concerns in the systems engineering of a rocket. Others include manufacturability, propulsion, changing flight regimes, safety, structures, economics, etc... All of these seem to have converged on a simple, more-or-...

23

The material used for the seal is silicone rubber. Example materials considered for NDS iLIDS are: Parker S0383-70 (as part of Gask-O-Seal product) Esterline ELA-SA-401 Silicone rubber is the only class of space flight-qualified elastomeric seal material that functions across the expected temperature range. NASA Glenn has tested three silicone ...

22

To complement, not attempt to replace, the other answers, I would like to propose a difficulty I see nobody having mentioned so far, but which could potentially be very problematic over such long time scales. Micrometeorite bombardment. Even after only 15 years in low (550 km) Earth orbit, we know that the Wide Field Planetary Camera II (WFPC2) on Hubble ...

21

The expression $v_e = \sqrt{\frac{2Vq}{m}}$ is a non-relativistic approximation. This is quite valid when the exhaust velocity is small compared to the speed of light, which is the case for ion thrusters made to date (exhaust velocity is on the order of $10^{-4}c$). A more precise expression is $${v_e}^2\left(1+\frac{2Vq}{mc^2}\right) = \frac{2Vq}m$$ No ...

20

Apparently the issue could not be addressed in time for the Apollo 13 mission as is evidenced by this note in the NASA archives available online. During the Apollo 13 flight the pogo effect had reappeared, this time on the second stage. Severe oscillations had forced an early shutdown (two minutes ahead of schedule) of the inboard engine. The NASA ...

19

I can answer the Shuttle part. The test in question was the Mated Vertical Ground Vibration Test (MVGVT). Here's how the stack looked in the test stand. Five configurations were tested Liftoff First stage (SRBs attached) early, mid, and late 2nd stage For the launch testing, the SRBs stood on hydrodynamic supports which "provided the vertical support ...

18

I thought it might be interesting (and hopefully helpful) to take a look at the education that astronauts actually have. For that, I decided to look at the list of current NASA astronauts (and current but not flight-eligible), and former NASA astronauts (there are some extremely interesting people in there, by the way). For the sake of this answer, I'm ...

17

They're part of the SpaceX reusable launch system development program. The intent is to make both first and second stages of the Falcon 9 and the Falcon Heavy reusable by returning them both to the launch pad, where they are to make vertical landings. Their technology demonstrator, Grasshopper, made eight successful test flights. Yes, it reduces the payload ...

17

Nitrogen is a relatively inert diatomic (N2) gas, but also importantly, while there are other gases that refuse to react with much anything even more so, like e.g. Helium, Nitrogen is cheap since it's often a byproduct of industrial processes. It is also frequently readily available at scientific facilities in its liquid form for being an extremely ...

16

The big difference is in weight. Satellites in Earth orbit can be much heavier than deep space probes, simply because it takes a lot of energy to launch something into an Earth-escape trajectory. Satellites are often in the region of 8 tons, while deep space probes are rarely above 1 ton. The materials are mostly the same. Aluminium for the structure, the ...

15

The biggest challenges are going to be what people have already mentioned - the funding (don't skirt over that comment, you did ask for the challenges), an energy source for 10,000 years, and how to make a flash or radio pulse based on parts that can last that length of time. Electronics, by the way, is a particular problem. I've heard people boast low ...

15

Radio may reduce some complexity, but it will introduce problems that wiring doesn't have. Limited bandwidth. Interference. You can separate wiring so it doesn't influence each other. Can't do that with radio: each receiver can hear all transmitters. You're introducing new points of failure. A radio transmitter or receiver contains loads of active ...

14

NASA has done an extensive report on this, and in fact, cryogenic hydrogen tanks are considered to be one of the greatest technical achievements that NASA managed. Much of this is specific to the Centaur upper stage, but here's a few interesting quotes from the article: Page 38 Bossart led Mrazek out into the factory yard, where a Centaur tank stood ...

14

This article provides great summary of Falcon 9 evolution, including changes in the Block 5 version. In short (from this article): Black interstage, landing legs, and raceway Retractable landing legs Redesigned composite overwrapped pressure vessel (COPV) which hold helium – Both to account for Amos-6 disaster and to handle many reuses Redesigned ...

13

You need a massive facility that can maintain a near vacuum while dealing with the engine exhaust. There are (were) a couple in the US. Plum Brook Station (Part of NASA Glenn) includes the In-Space Propulsion Facility (picture from this informative paper) Arnold Engineering Development Center (run by the DOD) includes the J-6 Large Rocket Motor Test ...

13

It is indeed difficult to find information on this building. As you can see in the photo below, it was part of a massive test facility at Marshall Space Flight Center: (Overview of MSFC; Mike Jetzer/heroicrelics.org) Some details of how the test stand worked can be found in the nomination form for the US National Register of Historic Places Inventory: ...

12

The issue with Sea Dragon and pressure instability is that the likelihood of pressure instability increases exponentially as the size of the combustion chamber and nozzle diameter increases linearly. Sea Dragon's bell was supposed to be over 75 feet in diameter and put out 350 meganewtons of force (about 5000% more than an F-1 engine). The F-1s had huge ...

12

As noted, the SpaceX plan is to build a rapidly reusable rocket. That is the only real way to get costs down. At the moment, no one has ever done what they are trying in several ways. What I find most interesting is the regular testing. Grasshopper and Grasshopper 2 (officially named F9R-Dev1 and it was tested into a lovely explosion as they hit an edge ...

12

This will be a subjective answer to a subjective question (I was not going to answer at all, but @called2voyage's link ([Good Subjective/Bad Subjective])1 (see @called2voyage's comment to the OP, above) emboldened me...). Please keep in mind that the experiences shared below were attained during a period of time lasting from the mid 90's to the early 00's. ...

12

tl;dr - each bay of the mast collapses as it is pulled into the cylinder. The ISS solar array mast is a truly ingenious mechanical structure which can be retracted into a remarkably small canister. It was developed by ATK and is called a Folding Articulated Square Truss (FAST) mast. This picture shows a FAST mast without arrays. The mast is composed of ...

12

The question seems to be primarily about rovers, which is covered in Hobbes' answer. However, there have also been a large number of landers, which have seen a fair amount of re-use: The Soviet Mars 2-7 landers of the 1970s were built in identical pairs. Even between the pairs, many components were re-used. The two U.S. Viking landers were essentially ...

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