Re: Russia and ESA start to Mars and Venus again

From: Hop David (hopspageHATESSPAaMmM_at_tabletoptelephone.com)
Date: 02/03/05 

Date: Thu, 03 Feb 2005 09:19:23 -0700

Anthony Frost wrote:
> In message <11004o2r3ftvr1f@corp.supernews.com>
> Pat Flannery <flanner@daktel.com> wrote:
>
> > Anthony Frost wrote:
> > > >Err, why? A Soyuz launcher can put a 1223kg orbiter in place around Mars
> > >so a 1300kg straight in lander to Venus sounds plausible. Using a Proton
> > >would give you about 3 times as much, around 4 (proper) tons.
> > > The atmospheric entry on Venus is pretty severe, so generally they would
> > have the lander proper ride inside of a spherical heatshield on the way
> > down. Then there's the matter of power supply for the vehicle in transit
> > as well as course correction and communication gear-
>
> I got the impression from the article that it was the all up weight,
> Mars Express included its "cruise stage" in that mass, as well as a
> reasonable science payload.
>
> > ...but isn't the Delta V change
> > needed for Venus higher than that needed for Mars?
>
> I'll possibly get Henry'd on it but I thought the difference wasn't that
> great. It is a bit higher, but nowhere near Proton over Soyuz higher.

This is what I get:

                 Depart DV Arrive DV Total DV Trip time Window each
Earth to Mars 2.94 km/s 2.49 km/s 5.59 km/s .71 years 2.14 years
Earth to Venus 2.65 km/s 2.71 km/s 5.20 km/s .40 years 1.60 years

These are for Hohmann transfers between circular, coplanar orbits. Mars
can vary substantially from this ball park because of its more eccentric
orbit.

>
> > * In fact, if you made the entry vehicle into the shape of a flat
> > conical aeroshell, you wouldn't even need parachutes for the landing due
> > to the high atmospheric pressure on Venus.
>
> If they're doing some atmosphere science on the way down I'd guess at a
> bit of parachute being used. A big aeroshell would get in the way of the
> nearby surface after landing unless you dropped it.
>
> Anthony
> 

-- 
Hop David
http://clowder.net/hop/index.html

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