Akatsuki Venus Climate Orbiter |
Akatsuki Venus Climate Orbiter |
Mar 13 2010, 11:29 AM
Post
#1
|
|
Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
I thought it was time to start a separate thread on this mission, launching soon
some good medium-resolution images of the spacecraft are available on JAXA digital archives http://jda.jaxa.jp/jda/p3_e.php?time=N&...mp;mission=4066 |
|
|
May 3 2016, 01:01 AM
Post
#2
|
|
Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
I just want to chime in a note of thanks to you for your work in translating these documents, pandaneko.
-------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
|
|
|
May 4 2016, 12:12 AM
Post
#3
|
|
Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
Page-30
Example 3: Clarifyinng mechanism for complex patterns (UVI+LIR) (1st character set after above in yellow box): In particular, complex abosrption patterns in dark area (2nd character set): Are solar light absorbing materials lifted from lower height? Are they newly chemically produced at cloud tops? Are they moved horizontally? What kind of convection, pulsage, random flow currents are involved? (3rd character set in yellow box): Very clear boundary between dark and light regions (4th character set): In particular, complex absorption patterns in dark area Is there a barrier of horizontal mixture of absorbing material and haze (translation unsure, P)? Is new aerosol produced in a particular area? (5th character set): Clarify air mass transport and change (?) process at cloud top from observing distribution of absorption materials and haze (UVI), cloud temp. variation with height (LIR), wind velocity disribution form cloud tracing P |
|
|
May 4 2016, 12:16 AM
Post
#4
|
|
Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
I have this nagging thought. In fact, I have had it for long time by now.
If Akatsuki was able to enter a kind of orbit around Venus with its smaller engines, then why did they bother with the larger engine that failed? They could have designed a craft with a few more of these smaller engines and made Akatsuki go around in a proper circle? Tha wouod have been a lot cheaper? P |
|
|
May 5 2016, 08:29 AM
Post
#5
|
|
Member Group: Members Posts: 247 Joined: 17-February 07 From: ESAC, cerca Madrid, Spain. Member No.: 1743 |
I have this nagging thought. In fact, I have had it for long time by now. If Akatsuki was able to enter a kind of orbit around Venus with its smaller engines, then why did they bother with the larger engine that failed? They could have designed a craft with a few more of these smaller engines and made Akatsuki go around in a proper circle? Tha wouod have been a lot cheaper? P Hello- You can get into orbit with big engines or with small engines. But if you plan to use a big engine, and then only have small engines, things get difficult. Look at the Dawn mission at Ceres. They have an ion engine, which has very small thrust. But the engine is designed to operate for a very long time. This was in the design, and the approach to Ceres was designed for the amount of thrust available. The main Akatsuki engine seems to have burned for about 3 minutes out of the planned 12 minutes. So the spacecraft did slow down significantly, but not nearly enough. So it went past Venus pretty fast. Later, some burns were performed, but I assume that the spacecraft was still moving fast when it returned to Venus. All they had available were the attitude thrusters. I do not now know anything about the Akatsuki attitude thrusters, but in general they are quite small compared to a main engine, say 1 to 5% as big. And they are not designed to fire continuously for long periods of time. Attitude thrusters are designed to give very short bursts that are very accurate. Akatsuki now had to use thrusters designed for short bursts, for a very long continuous burn. I suspect that the thrusters were never designed, let alone even tested, for such a long continuous burn. If I had been the propulsion engineer on Akatsuki, I would have been very afraid of a failure of one or more of the thrusters. So, the answer to your question is: you can use small engines or big engines. But if your mission is designed for one or the other, it is very very difficult to change the mission design because your hardware may not work. I hope this may have been helpful. Sorry if it is not. -------------------- --
cndwrld@yahoo.com |
|
|
May 5 2016, 08:37 AM
Post
#6
|
|
Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
cndwrid
Gracias y mucho obligado. Le entiendo muy bien. Thaks. P |
|
|
May 7 2016, 02:22 AM
Post
#7
|
|
Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
Page-11
(Page title): Akatsuki's health Akatsuki is currently flying along an orbit nearer to the sun than Venusian orbit. Consequently it is experiencing a harder thermal environment than originally planned. Therefore, we changed its attitude so that the most heat resistance face (+Z) will point to the sun. Akatsuki passed the 9th (final) nearest Sun point on 30 August 2015. At each point of the space craft the temp. is drecreasing as predicted, showing that Akatsuki is in good health (except the main engine). (on the left hand graph, vertical scale is solar radiation strength in W/mxm, and the horizontal scale is date) (Character sets on the graph from top to bottom are): Akatsuki (green) Solar orbit (just above green dotted lines) Transition (or transfer?) orbit (just above red dotted lines) Maximum solar radation on 17 April at 3665 W/mxm Venus (red in middle) VOI on 7 December with 2621 W/mxm Earth (blue in middle) Launch 21 May P |
|
|
Lo-Fi Version | Time is now: 22nd September 2024 - 03:10 PM |
RULES AND GUIDELINES Please read the Forum Rules and Guidelines before posting. IMAGE COPYRIGHT |
OPINIONS AND MODERATION Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators. |
SUPPORT THE FORUM Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member. |