# Tag Info

75

+1 Good question! It's not actually gold, but I think this is a common misconception, so allow me to elaborate for a bit. The stuff that you see satellites covered in is not normal foil, its just the outer layer of so-called "Multi Layer Insulation" or MLI. That means that there are several layers of foil, each separated by a spacer, so that transfer ...

62

I've done a lot of work on this subject with researchers and engineers at JPL, NASA Langley, and NASA Ames. There are some interesting things that come out of high-fidelity CFM (Computational Fluid Mechanics) modeling of entries or re-entries, and also from flight experience. This FAA tutorial segment is a good general reference for the principles involved. ...

49

No, heat shields are not as necessary on launch, at least not the same type as used in re-entry, which is what most people think of when the term "heat shield" is used in space. A re-entry heat-shield is only one type of Thermal Protection System (TPS), which is the more technical term for heat shield. There are heat shields in your non-electric car to ...

41

To reduce the force of the impact on landing the heat shield was designed to separate and be held on by a skirt that acted as an airbag. From the NASA list of Mercury illustrations: Figure 46: Impact attenuation When the heat shield was released the impact skirt would fill with air, but when the heat shield hit the water the air being forced out the holes ...

38

There is an atmosphere on Mars. An atmosphere ~1% as thick as Earth's sounds like it ought to 'basically not count as an atmosphere' but 1% earth's atmosphere is still quite a lot of gas! The pressure of Mars's atmosphere is about ten million times larger than outer space. I can't find it right now, but there's a quote about the Martian atmosphere, that says ...

37

Heat shields are only good for braking, not for acceleration. Remember that the key to being in orbit isn't to be high up but to go sideways really fast. Launching a spacecraft means accelerating it all the way to orbital speed. Conversely, reentering and landing means shedding all that speed again. It's fairly obvious that you need some means of ...

30

F9 can enter engine first because it isn't returning from orbital speeds. While fast, it's a fraction of the speeds something returning from orbit (or further) comes in at. So the engines are out as an entry surface, you need more protection. One way to achieve this is Dragon-style: put a heat shield on the bottom, and engines in the sidewalls. Great for ...

24

There's a Spinoffs from the Space Shuttle Program page hosted on the NASA Marshall Space Flight Center portal. According to it: Jewelry Design — Jewelers no longer have to worry about inhaling dangerous asbestos fibers from the blocks they use as soldering bases. Space Shuttle heat shield tiles offer jewelers a safer soldering base with temperature ...

22

The columbium jet nozzles themselves can take the heat, but "penetrations" of the spacecraft heat shield are a definite potential failure point, including penetrations for the Reaction Control System (RCS) jets. The design to preclude hot gas intrusion while preventing damage to the surrounding Thermal Protection System can be quite complex. The forward ...

17

The dimpled sphere may produce lower drag (though as Uwe points out I’m not sure if that is true in hypersonic flight). However, this does not mean that it will be better at surviving reentry. Higher drag implies a faster reentry and shorter exposure to extreme temperatures. Conducting heat to the core takes time, so even if the outer layer is ablating, the ...

17

An atmosphere does not need to be very thick to heat up a reentry vehicle significantly. And it should be noted that reentry vehicles entering the Earth's atmosphere get heated up at a pretty high altitude with thin air as well. The point of maximum heating is also not necessarily the same as the point of maximum acceleration. At near-orbital speeds, two ...

15

Musk indicated that Dragon 2 could be reused "with minimal rework and fueling" about 10 times between overhauls. This is the target number but these are early days. The previous ablative shield was dumped in favor of a more advanced design. The goal then, for heat shield, engines and other major components would be at Least 10 flights, in theory. Regards ...

13

If you're only referring to surviving the phase of peak heating, then Mars is easier than Earth. The entry velocity is more like 6 to 7 km/s at Mars vs. 11 to 12 km/s at Earth, due to their respective gravity and typical approach velocities. Everything else about landing on Mars is harder, due to the low density of the atmosphere. The density can be a ...

12

The outside of the Command Module is covered by a heat shield. According to this report (page 5), the forward portion of the heat shield (i.e. the part covering the cone-shaped part of the CM) is a 0.5" thick layer of phenolic resin. It is covered by several outer layers: a pore seal, a moisture barrier (which is white) and the outer layer is a silvered ...

12

Astronaut spacesuits use gold (thin layer) Gold coating protects eyes from harmful sunlight Gold is also used by NASA in the construction of spacesuits. Because of its excellent ability to reflect infrared light while letting in visible light, astronauts’ visors have a thin layer of gold on them to protect their eyes from unfiltered sunlight. Satellites ...

10

It's not the surface area by itself. There are two main factors. The first is the ballistic coefficient, $\beta$, which is the mass divided by the product of the surface area and the coefficient of drag: $\beta={m\over C_D A}$. The second is the lift over drag (L/D) of the vehicle, which for these blunt vehicles is usually obtained with an offset center ...

10

NASA is working on an inflatable heat shield. Not quite a blimp, but a heat shield that's inflatable to a size much larger than the probe it's attached to. The extra area helps decelerate the spacecraft. So inflatable structures can be made to withstand the heat of reentry. Because Mars' atmospheric density is only 0.6% of Earth's, a blimp's lift will ...

10

There is a fixed amount of energy which has to be dissipated. You can, to some extent, choose how fast this is done -- more air resistance (either by getting into thicker air or having a bigger surface) dissipates it faster, with higher g forces. Less air resistance dissipates it slower, but you do have to make sure to get rid of it all before you hit the ...

10

Already a lot of good answers, so just one additional aspect to the explanation: When orbiting Mars, the vehicle has a lot of kinetic energy that has to be reduced to zero before landing. Coming from a low orbit, you have to somehow slow down from 3.5 km/s (8000 mph) to zero. Over non-atmosphere bodies like the moon, the only chance to slow down is firing ...

9

The outside of the Soyuz is covered in multilayer vacuum-screen thermal insulation. Its Russian acronym is ЭВТИ, long for экранно-вакуумная теплоизоляция or Shield Vacuum Thermal Insulation. It apparently is in many layers of metalized film and fiberglass cloth. Its purpose is to protect the modules during ascent and orbit. It doen't seem to be designed to ...

9

There are several misconceptions in your question/proposal: The Orion and the Dragon as well as other reentry capsules do not fly with the cone tip forward. They fly with the blunt "bottom" side forward. (fixed in the revised question) Plasma is created by the very passage of the vehicle through the air at high hypersonic velocities. At lower velocities, ...

9

Surprisingly the answer is yes there was studies done on that subject. A simple google search could yield this result: BUOYANT PLANETARY ENTRY https://apps.dtic.mil/dtic/tr/fulltext/u2/642361.pdf In this study, it was assured that the large buoyant volune is deployed prior to atmospheric entry. The effect of buoyancy on the entry dynamics was ...

8

The CST-100 heat shield is replaced each flight because it is discarded as part of the landing process. The capsule has airbags, between the heat shield and bottom of the capsule. As the parachutes slow it down for landing, it discards the heat shield, inflates the airbags, and lands on the ground. Thus they can never reuse a heat shield, they throw it ...

8

The heat shield (TPS) is not meant to protect the spacecraft from dust impacts. The statement is not quite accurate and (from a recent search) seems to have been removed from site. As an engineer on the Parker Solar Probe team, I have been involved in the Preliminary and Critical Design Reviews for the mission which include presentations on Dust Protection ...

8

Take the super-optimistic 500 kJ/kg energy density of flywheel energy storage. In reality 10% of that would be a great result. $E_k = {1 \over 2} mv^2$ so 0.5*1kg*(8km/s)^2 = 32MJ per kilogram of orbital mass. If the craft was nothing but the flywheel, you'd still receive 64 times more energy than you can most optimistically contain. Your flywheel would ...

8

Apparently, black was chosen despite its thermal properties. This 2005 paper was written at the end of the assessment phase where technical feasibility of the mission has been demonstrated. It shows several options were studied, including a white shield. Materials with a/e (absorption/emission constant, ed.) close to 1 could also be used. Typically ...

8

The problems with temperature insulation for a situation like Venus, where you are surrounded by very high temperatures on all sides: Insulation is heavy. Insulation slows down the gradual spread of heat inwards towards your vulnerable interior, but it cannot stop it. All power sources, electronics, and other active, useful equipment that would be found ...

8

Aerogel doesn't have much mechanical strength. Orbital velocity is say 7800 m/s and you have to decelerate over say 300 seconds. Even if it's done carefully there are 2 or 3 gees of peak deceleration. So imagine your spacecraft sitting on the ground resting on its aerogel heat shield with two or three more spacecraft stacked on top of it. It will likely be ...

8

Some of the information here comes from Wikipedia, some of it comes from my engineering intuition which may be wrong. There are probably at least three reasons for building the leading edge in many sections. Making single large structures is much harder than making several small ones, so it is a lot easier to make the leading edge out of a number of ...

7

The main problem is thermal control: you need a heatshield on your spacecraft to survive through the close pass. It is a solved problem though, meaning that NASA is planning to send a mission in 2018 to explore the close environment of the sun as low as 8 solar radii: http://solarprobe.jhuapl.edu/mission/index.php https://en.wikipedia.org/wiki/...

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