Communities

Writing
Writing
Codidact Meta
Codidact Meta
The Great Outdoors
The Great Outdoors
Photography & Video
Photography & Video
Scientific Speculation
Scientific Speculation
Cooking
Cooking
Electrical Engineering
Electrical Engineering
Judaism
Judaism
Languages & Linguistics
Languages & Linguistics
Software Development
Software Development
Mathematics
Mathematics
Christianity
Christianity
Code Golf
Code Golf
Music
Music
Physics
Physics
Linux Systems
Linux Systems
Power Users
Power Users
Tabletop RPGs
Tabletop RPGs
Community Proposals
Community Proposals
tag:snake search within a tag
answers:0 unanswered questions
user:xxxx search by author id
score:0.5 posts with 0.5+ score
"snake oil" exact phrase
votes:4 posts with 4+ votes
created:<1w created < 1 week ago
post_type:xxxx type of post
Search help
Notifications
Mark all as read See all your notifications »
Q&A

Comments on High-Energy Exhaust Shielding for Far-Future Drive

Post

High-Energy Exhaust Shielding for Far-Future Drive

+2
−0

Imagine a far-future spacecraft drive that accelerates its reaction mass to a small fraction the speed of light (say, 1,000 km/s). Say the mass flow rate to the drive were 1kg/s, and say the reaction mass were hydrogen. what effect would the resulting exhaust have on humans? On other spacecraft? If fired within an atmosphere comparable to Earth's at sea level, how would these effects change? What sort of shielding would be needed to protect a spacecraft or EVA suit and the people inside from damage or injury? How far would you have to be from the nozzle to safely remain inside the exhaust jet in a vacuum? In an atmosphere comparable to Earth's at sea level? How would this change with higher exhaust velocity, say 30Mm/s?

Such a jet would put out 500GW of power, and assuming the jet diverges, the intensity drops with the inverse square of the distance. This question was discussed here, but the provided answer deals primarily with the force exerted on spacecraft in the jet and is more focused on less powerful engines with a much lower exhaust velocity (40-100km/s). This question deals more with considerations that must be made with exhaust velocities at a significant fraction of the speed of light.

History
Why does this post require moderator attention?
You might want to add some details to your flag.
Why should this post be closed?

2 comment threads

Your numbers don't add up. (2 comments)
Relativistic speed (2 comments)
Relativistic speed
Canina‭ wrote about 2 years ago · edited about 2 years ago

I'm not sure 1000 km/s (1 Mm/s) really qualifies as relativistic speed. Even 30000 km/s (30 Mm/s) seems borderline. Consider the special relativisitic colinear velocity addition formula; the factor c² likely still dominates, suggesting that relativistic effects would be small. Compare for example Accretion by a Neutron Star Moving at a High Kick Velocity in the Supernova Ejecta, which indicates velocities of that order of magnitude (10³ km s^-1); also Wikipedia says Type II supernovae can propel Sun-mass objects at >500 km/s, which again is about the same order of magnitude.

Josh Hyatt‭ wrote about 2 years ago

Thank you for pointing this out. I had been under the impression that something moving at 10% the speed of light would experience some relativistic effects on a significant scale. I've corrected the question.