Welcome to Space Exploration Stack Exchange
We're a little bit different from other sites. Here's how:
Ask questions, get answers, no distractions
This site is all about getting answers. It's not a discussion forum. There's no chit-chat.
Just questions...
...and answers.
Good answers are voted up and rise to the top.
The best answers show up first so that they are always easy to find.
The person who asked can mark one answer as "accepted".
Accepting doesn't mean it's the best answer, it just means that it worked for the person who asked.
How close was Philae to escape velocity during its first bounce?
ESA indicates that the first bounce lasted two hours and reached a height of 1 km. With the extremely weak surface gravity and low escape velocity of the body (< 1 m/s), and other publicly available information regarding the comet's mass properties and the landing site location, can we estimate how close the lander came to drifting away into space?
9,9691 gold badge42 silver badges58 bronze badges
2 Answers
It was never close. Rosetta did not have escape velocity when it ejected Philae. So as long as Philae was ejected in the retrograde direction, Philae would not have escape velocity either. After the bounce, Philae would have even less energy due to landing gear attenuation and would therefore be even farther from escaping than it was pre-bounce.
10k2 gold badges39 silver badges71 bronze badges
The new report says Philae was moving at 38 cm/s.
Using Russell's figure of 0.886 m/s as escape velocity, we have 43% of escape velocity.
52.9k10 gold badges161 silver badges327 bronze badges
Get answers to practical, detailed questions
Focus on questions about an actual problem you have faced. Include details about what you have tried and exactly what you are trying to do.
Not all questions work well in our format. Avoid questions that are primarily opinion-based, or that are likely to generate discussion rather than answers.
Questions that need improvement may be closed until someone fixes them.
Tags make it easy to find interesting questions
All questions are tagged with their subject areas. Each can have up to 5 tags, since a question might be related to several subjects.
Click any tag to see a list of questions with that tag, or go to the tag list to browse for topics that interest you.
How close was Philae to escape velocity during its first bounce?
ESA indicates that the first bounce lasted two hours and reached a height of 1 km. With the extremely weak surface gravity and low escape velocity of the body (< 1 m/s), and other publicly available information regarding the comet's mass properties and the landing site location, can we estimate how close the lander came to drifting away into space?
9,9691 gold badge42 silver badges58 bronze badges
You earn reputation when people vote on your posts
Your reputation score goes up when others vote up your questions, answers and edits.
As you earn reputation, you'll unlock new privileges like the ability to vote, comment, and even edit other people's posts.
At the highest levels, you'll have access to special moderation tools. You'll be able to work alongside our community moderators to keep the site focused and helpful.
Improve posts by editing or commenting
Our goal is to have the best answers to every question, so if you see questions or answers that can be improved, you can edit them.
Use edits to fix mistakes, improve formatting, or clarify the meaning of a post.
Use comments to ask for more information or clarify a question or answer.
You can always comment on your own questions and answers. Once you earn 50 reputation, you can comment on anybody's post.
Remember: we're all here to learn, so be friendly and helpful!
It was never close. Rosetta did not have escape velocity when it ejected Philae. So as long as Philae was ejected in the retrograde direction, Philae would not have escape velocity either. After the bounce, Philae would have even less energy due to landing gear attenuation and would therefore be even farther from escaping than it was pre-bounce.
10k2 gold badges39 silver badges71 bronze badges
Unlock badges for special achievements
Sign up to get started
Signing up allows you to:
- Earn reputation when you help others with questions, answers and edits.
- Select favorite tags to customize your home page.
- Claim your first badge: Informed
Space Exploration Stack Exchange is part of the Stack Exchange network
Like this site? Stack Exchange is a network of 181 Q&A sites just like it. Check out the full list of sites.
