54
votes
Accepted
How did the Apollo 11's Eagle ascent stage find the CSM after leaving the Moon?
The process was a great deal more sophisticated than pointing and thrusting, and the CSM was cooking along at over 1600 m/s, circling the moon every 2 hours.
Mission control, however, had fairly ...
- 164k
40
votes
Accepted
Given small computational resources, how was navigation implemented? (Not samples of old guidance software)
In many of the early probes, up until close to Apollo there were not true computers on space probes. All computing was done on Earth and the onboard electronics was known as a sequencer, for Pioneer ...
- 19.2k
33
votes
Accepted
How did astronauts using rovers tell direction without compasses on the Moon?
The Lunar Roving Vehicle did have a (form of) compass. It was gyroscopic rather than magnetic, thus it needed calibration when first powered up using the sun angle as a reference. It's in the upper ...
- 164k
30
votes
Accepted
How did astronauts navigate the Lunar Roving Vehicle (LRV) over the surface of the Moon?
The navigation system used a combination of magnetic pickups in the wheels (to count how many turns each one has taken) and a directional gyro. This allowed both turn angles and distances travelled to ...
- 5,168
28
votes
How will DART be able to hit a 170 meter rock dead-center at over 6000 m/s? What technologies will be use and how will they work together?
Didymos will be roughly 11 million kilometers (6.8 million miles) from Earth at the time of the DART impact.The round trip time for a radio signal from DART to the control center on Earth will be ...
- 48.3k
27
votes
Given small computational resources, how was navigation implemented? (Not samples of old guidance software)
(originally answered to "Samples of old guidance software")
The first that comes to mind is the Github repository of the Apollo 11 Guidance Computer (AGC). The repository has both Command Module and ...
- 13.6k
26
votes
Accepted
Lunar Terrain Model in Apollo Guidance Computer
It was very simple. Five sloped straight lines.
The terrain is modeled by a series of line segments leading to the
nominal landing site. Each line segment is
defined by a pair of single-precision ...
- 171k
25
votes
How would blockchain be integrated into spaceflight? Have any methods been proposed yet?
Blockchain is a very poor solution to a specific problem: achieving ledger consensus among a large number of agents when there is substantial incentive to corrupt the record, and the entries in the ...
- 164k
22
votes
Accepted
Radar altimeter in a space shuttle
The radar altimeter was intended only for landing, to provide a direct, precise measurement of the altitude of the vehicle above the runway. It locked on around 5000 feet altitude but was primarily ...
- 171k
21
votes
Accepted
How does a space vehicle which carries Curiosity or Spirit rover reach a planet?
Movies are misleading.
Space is enormous, and almost entirely empty. Even our ”asteroid belt” is mostly empty space; we have flown several missions straight through the belt to the planets beyond ...
- 164k
19
votes
Most accurate attitude determination system in spacecraft?
TL;DR
Star trackers are by far the most precise. Sun sensors are used for coarse knowledge and IMUs only for estimating the attitude during a maneuver.
Details
Attitude determination typically relies ...
- 6,080
16
votes
Accepted
Accelerometer in space
Yes, a properly functioning accelerometer that is stationary relative to the surface of the Earth will read the acceleration due to gravity. If it's a very good accelerometer, you could also see the ...
- 58.2k
16
votes
Accepted
What was the globe instrument in Vostok 1?
From russian wikipedia:
Another instrument helped to the pilot to decide when to start manual operation to return to Earth - it was a small globe with a clock mechanism, which shows the (calculated, ...
- 2,994
16
votes
How did astronauts using rovers tell direction without compasses on the Moon?
The rovers used a gyroscope-based navigation system.
The Lunar Roving Vehicle (LRV) navigation system consists of a
directional gyro, a set of incremental odometers, and a hybrid
analog-digital ...
- 171k
15
votes
Given small computational resources, how was navigation implemented? (Not samples of old guidance software)
I am a software developer and with all the resources available today I cannot fathom where one could even start such an endeavour.
There are plenty of computer-based systems to this day that have to ...
- 71.4k
15
votes
Accepted
Which is more accurate, a Saturn V IU or an iPhone?
The ST-124-M3 platform wins, hands down.
The ST-124 was flight tested on the Saturn I flights. I found the corresponding test report "SATURN I BLOCK II GUIDANCE SUMMARY REPORT" from February ...
- 13.6k
14
votes
How did astronauts navigate the Lunar Roving Vehicle (LRV) over the surface of the Moon?
Well if they did slip their navigation they can follow their tracks back to the LM. They planned for this in case of total breakdown, how much more for nav error.
- 852
13
votes
Accepted
How might Earth's location be referenced in stellar terms?
Like the lower left part of the image below.
Define a set of pulsars through describing proportions between their frequencies. Define distances from each of them. This uniquely identifies a point in ...
- 54.1k
13
votes
Accepted
When did Houston figure out where the Eagle had landed?
They used the rendezvous radar on the LM to pinpoint the CSM's relative direction, and worked backwards from that info and the CSM's location in order to pinpoint the LM.
Here's the commentary from ...
- 164k
12
votes
Accepted
Could a swarm of probes autonomously establish orbit around an asteroid?
Let's break your question into separate tasks:
Autonomous orbit determination (autonomous because the DSN won't be there to help you when you need it)
Autonomous attitude determination
Situational ...
- 11.4k
12
votes
Accepted
How are GPS satellite clocks synchronized with each other in the earth's frame of reference?
The satellites' location is very accurately determined using ranging techniques, where a pulse is sent from a ground station to the satellite and the satellite responds very quickly, with a known time ...
- 120k
12
votes
Height of navigation satellites above Earth
For satellite navigation, you are most likely using the Global Positioning System, which uses six planes of satellites at an altitude of 20,180 km. However, many systems can also use the GLONASS ...
12
votes
Spacecraft Navigation
Navigation to high accuracy is done using radiometric tracking. There are scads of references, such as here, here (don't let the Russian language on the title slide scare you off!), and here, that ...
- 18.1k
12
votes
Accepted
How would the state vector be updated in the Apollo Guidance Computer during coasting to/from the moon if communication with Earth was lost entirely?
The restrictions you are quoting only apply to the LGC, the computer in the Lunar Module. The Command Module Computer does not have these restrictions (compare the section about the Coasting ...
- 1,971
12
votes
Accepted
Perseverance Rover to drive carefully for months while helicopter hangs from underside?
The helicopter and the deployment assembly are protected by a "debris shield" which is only dropped shortly before helicopter deployment. This shield is formed out of carbon fiber and fully ...
- 16.2k
11
votes
Accepted
How do probes locate themselves?
Interplanetary probes generally don't have enough equipment on board to calculate their own position. So the location of a probe is measured by ground control, using data from the probe.
Distance ...
- 123k
11
votes
Accepted
Autonomous Navigation for deep space missions
Positions over time can be used to determine velocity, not just in the obvious way but more accurately than that using a model of the gravity field the spacecraft is moving in, dominated by the Sun ...
- 58.2k
11
votes
Accepted
A gedanken on being able to navigate back to Earth
Answering the corrected question, "I was interested in if we could look at the stars and constellations in the sky to get back to earth. So assume navigation only by looking at the space." The answer ...
- 371
11
votes
Perseverance Rover to drive carefully for months while helicopter hangs from underside?
No, Perseverance will not drive for months with the helicopter stowed on its underside.
From the Surface Phase of the Mars 2020 Perseverance Launch Press Kit I got the information below.
The first 30 ...
- 7,359
10
votes
Accepted
What is the maximum acceptable latency in rocket control computers?
The STS roll control program controlled attitude in response to sensed velocity, rather than attempting to control the trajectory directly. This portion of the flight wouldn't be particularly latency-...
- 164k
Only top scored, non community-wiki answers of a minimum length are eligible