48 votes
Accepted

What eliminates the velocity when occupants return from ISS to earth, and how much?

Nearly all the velocity is cancelled by atmospheric deceleration of the descent module, before its parachutes are deployed. ISS orbital velocity is around 7700 m/s. An initial retro-burn of the ...
44 votes
Accepted

Why are spaceship capsules frustum shaped?

The capsules designed to reenter the atmosphere have to slow down from about 8 km/s to zero by the time they get to the ground. They actually don't use the part that looks like a cone to do that. They ...
28 votes
Accepted

Do exploration spacecraft enter Mars atmosphere against Mars rotation, or on the same direction?

There is always a benefit to entering a planet's atmosphere with matching rotation. In the case of Earth, the difference is a rather huge 920m/s effective airspeed between reentering prograde or ...
26 votes

What eliminates the velocity when occupants return from ISS to earth, and how much?

The process is described here, which answers nearly all of your question. The reentry burn removes about 120 m/s of velocity from the capsule (that's your 1) and the final impact is 15 miles per hour ...
  • 19.1k
24 votes
Accepted

Bounce off the atmosphere at reentry?

Yes, a capsule cannot literally bounce off the atmosphere and its kinetic energy must be reduced by an encounter with the atmosphere, rather it would just pass through the atmosphere and back into ...
  • 4,183
18 votes
Accepted

Why are LEO satellites not aerodynamically shaped?

Why are LEO satellites not aerodynamically shaped? The need for electrical power overwhelms the need to reduce drag. That means a sizable cross sectional area to incoming solar radiation. Sometimes ...
  • 68.6k
18 votes
Accepted

What is the word for using atmosphere to dissipate kinetic energy during reentry?

I can't say that the terminology is consistent across all users, but where I work (at JPL) we use aerobraking to refer to many light dips to lower an orbit, aerocapture to refer to a single deep dip ...
17 votes
Accepted

Can a reentry be done slowly?

Not without propellant. Or at least not easily. However the "why" is a bit tricky. This is far from the whole story but one of the problems is that generating enough lift to keep you from diving too ...
  • 3,382
17 votes
Accepted

Would it be feasible to decelerate a crewed vehicle from ~25 km/s only using the atmosphere of Mars (in the context of an "express transit")?

Nope, sorry. Completely disregarding the (enormous) heat factor of the aerobraking. The requirement specifies manned. The path through Mars' atmosphere will be very nearly a straight line. A bit of ...
16 votes

Multiple aerobraking

This works well in reality too, and helps to reduce heat loads. The reason this is not used is the fact that you must then pass through the Van Allen radiation belts multiple times, where you ideally ...
16 votes

How do we control a Reentering Capsule in the denser part of the atmosphere?

The entry vehicle for the Apollo missions is the command module (CM), which has a symmetric body with an offset center of gravity (c.g.). This offset c.g. causes the CM to trim ...
15 votes
Accepted

Multiple aerobraking

This is used in reality, although it is not as easy to do in real life as it is in Kerbal Space Program. Such passes dramatically increase the heat that the capsule is forced to deal with, and as a ...
  • 120k
14 votes

How do we control a Reentering Capsule in the denser part of the atmosphere?

For Gemini, Apollo, and Soyuz capsules, lift is achieved by offsetting the center of gravity of the reentry module from the center line of the craft. This is represented in your diagram by the "...
13 votes

How can delta-v and aerobraking as shown in this chart be explained?

Here's the original source of the diagram: https://www.reddit.com/r/space/comments/29cxi6/i_made_a_deltav_subway_map_of_the_solar_system/ Your concerns are also discussed there. 27000m/s is a very ...
12 votes
Accepted

What are the difference in energy costs for entering Venus vs Mars vs the Earth?

Aerobraking is most definitely used at Mars. Going from about 6000 m/s down to 100 m/s is done entirely with aerobraking, first with a heat shield, and then with a parachute. The last bit from 100 m/...
12 votes

Gliding into the atmosphere

It most certainly won't hurt anything. From FAA's document on returning from space, there is a very interesting chart, which I've included below. So the maximum g load is almost always at around 4500 ...
  • 120k
12 votes

Can a reentry be done slowly?

It is possible to do a slow and cool reentry. But it would be extreamly expensive. Just slow down from orbit speed to subsonic speed above the atmosphere and then fight gravity until it is possible ...
  • 47.9k
11 votes

How can aerobraking be used to enter high orbit without landing?

The idea with aerobraking is usually to do something like the following: Make your orbital insertion burn as usual, but instead of slowing all the way down into your final orbit, slow down just ...
  • 120k
10 votes

How can delta-v and aerobraking as shown in this chart be explained?

The calculations for Ulysse Carion's chart were done by Curious Metaphor. If you go the this Reddit thread, you'll see a conversation between Curious Metaphor and I. For years I made delta V charts ...
  • 15.3k
10 votes
Accepted

Mathematically, what is the argument in favor of skipping reentries?

The two systems that I know of that were qualified for skip entry, Apollo and Shuttle, did so purely for cross-range capability. The skip entry would have been used for an emergency return that could ...
9 votes
Accepted

When does an aerobraking space craft create a sonic boom?

How many grains of sand does it take to form a heap? An orbiting spacecraft is flying many times faster than the speed of sound. It's starting in atmosphere too thin to sustain an audible shock wave. ...
9 votes
Accepted

Could a reentry powered monorail and flywheel make a kinetic engine for lift?

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 ...
  • 53.4k
9 votes

Do exploration spacecraft enter Mars atmosphere against Mars rotation, or on the same direction?

Space craft will tend to enter orbit counter clockwise as viewed from the northern hemisphere. This is due to the fact that most objects in the solar system orbit and rotate this way with the ...
  • 6,483
7 votes

How can delta-v and aerobraking as shown in this chart be explained?

A 250km periapsis Earth orbit won't produce significant atmospheric drag. The inbound-aerobraking-possible notations for orbits are assuming that you dip lower into the atmosphere in order to slow ...
7 votes

How can delta-v and aerobraking as shown in this chart be explained?

Adding to @Rikki-Tikki-Tavi answer. For destinations where aerobraking is possible, and you have a sufficiently heat and acceleration hardened vehicle, it's possible to cheat. The map shows how much ...
  • 168
7 votes

Gliding into the atmosphere

You can't just slow it down over many orbits I think the question is suggesting letting a little bit of drag slow the Cessna down until it's at a normal speed before gliding through the atmosphere. ...
  • 2,041
7 votes

What will Max Q for descent be?

According to https://www.flightclub.io/results/?code=SS10 , reentry Q for flights like SES-10 peak at almost 92kPa at T+434 sec, about 3x the ascent max Q. The reentry prep burn brings velocity down ...
7 votes
Accepted

Starting refueled in LEO, how much payload could a heat-protected Starship softly land on Mercury after a gravity assist from Venus?

A single Venus flyby helps, but it does not make the journey possible for Starship. Below is a plot of 2025-2030 trajectories from Earth to Mercury that flyby Venus once. They are plotted by the Earth ...
6 votes

How can aerobraking be used to enter high orbit without landing?

The "high Mars orbit" being referred to is an elliptical orbit with a low periapsis and a high apoapsis. I usually see something like a one-day period orbit. The idea is to reduce the amount of fuel ...
6 votes

Gliding into the atmosphere

First of all, the heat shields aren't there just for the dense atmosphere with high deceleration, the upper atmosphere part of reentry also generates heat. If you had a craft that could fly in the ...
  • 511

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